PDA

View Full Version : Concrete Floor Thickness for Shop



firbikrhd1
04-29-2013, 07:07 PM
Perhaps some experienced folks here can give me some thoughts on the thickness of a shop floor. Currently I am building a new home with a shop in the basement. The plan is to have my 10" Logan lathe, a 12" Vernon Shaper, an Index Model 40 mill to start. The future may hold a 13X40 lathe and a horizontal mill as well. The concrete floor is planned to be 4" thick but for only the cost of materials I can make it 6" if that is necessary. I also have the choice between fiber reinforced concrete or the use of re-bar or road mesh for reinforcement. The contractor is advising the fiber reinforced concrete but I have no experience with it. Steel is great as long as it is properly placed in the slab and doesn't end up in the dirt or near the top of the finished floor. There is also the choice of 5000 psi material.
All this cost money of course and there's no point in spending it unnecessarily. If a 4", 3000 psi slab with fiber reinforcement is adequate, great, if it's inadequate I'll step up to what is. I have no doubt that 4" will work with the little Logan an the Index mill. The shaper will probably be OK too because it doesn't depend upon the floor to prevent flex. The larger lathe is my real concern as I realize when it comes to machining everything is "rubber" to a certain extent. Any recommendations as to what is adequate for something like this are welcome.
Thanks in advance.

pgmrdan
04-29-2013, 07:22 PM
I had a floor put in my outbuilding about 3.5 years ago. Today I called the guys to find out how much it will support because I'm getting a Bobcat skid steer delivered tomorrow. The specs say the concrete should hold over 10,000 pounds by itself. It can hold more because it's reinforced with 1/2" rebar on 36" centers. The concrete is 4" thick.

HTH,
Dan

flylo
04-29-2013, 07:23 PM
I think 4" is fine with fiber. Remesh is normally left on the dirt so unless done right does no good. JMHO

Duffy
04-29-2013, 07:27 PM
The 4" fiber reinforced concrete should be just fine, with ONE condition:- make sure that the granular base, (crushed stone I guess,) is compacted with a plate compactor. In most cases it is just raked level and cracks are guaranteed.

The Artful Bodger
04-29-2013, 08:15 PM
I think 4" is fine with fiber. Remesh is normally left on the dirt so unless done right does no good. JMHO

I would not say normally around here. The mesh is laid on top of a plastic damp course membrane and is supported by whatever is handy in the way of small wooden blocks or purpose made plastic stools.

mickeyf
04-29-2013, 08:44 PM
Not to over-think this, but you could make the spot where the heaviest machines are going to go thicker, and leave most of it economically thin. (Of course you'll never move them...)

lakeside53
04-29-2013, 08:47 PM
It all depend on the bearing capability of your sub-soil. If you are on glacial till (like me), 4 inches is fine. If you are on peat bog crap, deal with it by applying the appropriate (look up your local building codes for guidance) raft of granular support material before even considering 4 inches. Rebar should be in the bottom 1/3 and supported on small concrete blocks that are wired to the rebar -called "dobbie blocks" around here. 12 inch or 24 inch "squares" (run both directions) of no 4 rebar are typical. Dumping it on the bottom and pullling it up with a rake as you pour is a joke.

Gary Paine
04-29-2013, 08:58 PM
Currently I am building a new home with a shop in the basement. ....... Any recommendations as to what is adequate for something like this are welcome.

A Florida house with a basement:confused:

My basement has a 4 inch floor, lighter machines, tons of metal;) and a lot of cracks. If the power goes out on my sump pump, water will start to come up the cracks. If I EVER did it again, I'd use reinforced 5 or 6 inch.

You may be doing a walk out, but if not, consider an outside exit with a locking Bilco style door on top and steel door at the bottom. It'll make puttting machines inside a whole lot easier.

flylo
04-29-2013, 09:01 PM
That's the way road & commercial work but residential they are supposed to take the hooh on the come along but every slab I've ever peeled up the wire was on the dirt doing no good. You guys do things right!

I would not say normally around here. The mesh is laid on top of a plastic damp course membrane and is supported by whatever is handy in the way of small wooden blocks or purpose made plastic stools.

garyhlucas
04-29-2013, 09:12 PM
I'd go 6" with 6 x 6 steel mesh reinforcing. Ideally the reinforcing should be centered in the slab. Drive some rebar i nthe ground and wire the mesh to it so it stays in the right place. A few years ago I had to level a CNC lathe that weighed about 6,000 lbs. The lathe had 6 feet. As I adjusted the levelers I could tell it was the floor moving up and down, not the lathe! I got it level, but I'll bet a fork truck going by would change it. They also had a 72" x 200 Hp Toshiba blanchard style grinder. I had to do some trouble shooting and had the manual out. The manual said the grinder needed a 4 foot thick reinforced foundation! It was sitting on a 6 inch thick floor. The operator told me he was always adjusting it, wonder why! You will only regret spending a little extra one time. You will regret it being to thin forever.

firbikrhd1
04-29-2013, 09:19 PM
A Florida house with a basement:confused:

This will be a new home in the mountains of NC. S. FL is where I was born and lived my entire life. Sadly, it isn't the same place in far too many ways. It certainly isn't where I want to spend my retired life.

darryl
04-29-2013, 09:27 PM
I was taught that reinforcing mesh or screen- whatever you call it- should be placed from one third to halfway up in the thickness of the slab. One third up helps the concrete bear high loading on small areas, and halfway up helps the slab take an uneven settling of the ground better. I don't recall the specifics, but I think there's a formula for the mesh size and gauge, and it includes the thickness of the slab.

Several years ago I poured a slab to rebuild my garden shed onto, and also to be able to park a vehicle on. I went with 5 inches thickness, and 4 inch wire mesh. Seems to me the wire thickness was about 3/16 or so. The ground under it varies in density- parts were quite soft where a tree had been removed and deep roots remain, while other areas were hard and well packed. I didn't want the slab cracking, and I expected the ground to drop out from under it in places, which has happened. The slab itself has never cracked. I had figured that 5 inches thick with 4 inch mesh would be about optimum, and the cost seemed within reason. I would do it the same way again. And yes, I did suspend the mesh properly.

CCWKen
04-29-2013, 10:06 PM
Four inches is standard but there's more to it than that. There's a big difference between 1500psi concrete watered down for flow that some contractors use and properly mixed and laid 4500psi concrete. If you spec out 2500-3500psi and don't allow the contractor to water it down, you will have no problem over a properly prepared site.

polepenhollow
04-29-2013, 10:35 PM
I had a 6" slab poured in my shop-garage for cars and machines. It was on compacted fill. The fill was let to settle and then there was added gravel w/ a plastic membrane over it to thwart soil moisture infusion.
A 6" grid mesh was used at 3" depth in the slab. The mesh was held in place, mid slab, by junk concrete blocks of fill and re-bar driven into the ground. The re-bar was wired to the mesh to keep the mesh mid slab, at 3", during the pour.
This was for a floating slab in the interior of the shop..
The perimeter foundation walls were set to the proper depth with the required footing, per code.
The contractor wanted one 1/2" rebar on the perimeter. I requested two 1/2" rebars to be used.
Yes, it did cost at that time $100 or so more, but the building is unmoved and rigid.
It has held up well for 20+ years..

Mr Fixit
04-29-2013, 11:09 PM
I built my shop 3 yrs ago with a 6" slab and 8" wire mesh on dobbies. The one thing I might suggest is not only put down a vapor barrier but consider rigid foam board of the non foil type as an insulator. This is what i did and then I put a 3/4" pex piping system on top of the wire mesh for a radiant heat system. I have not gotten to that yet but it's there and for less then $300.00 in parts it can provide a very comfortable work environment. As I use the shop now with a electric heater the shop stays quite warm even when the heat is off. Just another idea to consider,

Mr. fixit for the family
Chris :)

duckman
04-30-2013, 12:08 AM
For what it's worth my slab is setting on 24"s of plate compacted crushed stone, I over killed the rebar front to back it's on 12" centers side to side 20" prior to the rebar foil bubble foil was put down, then 4,000# concrete 8"+ thick, 6 winter in the Northeast hasn't moved or cracked, and no grooves cut into it.

Spend it now and not worry about it cracking or moving, my 16' X 28' slab took 13 yards which includes the front ramp which is 8' wide and 6' long and about 6"s thick.

flylo
04-30-2013, 12:38 AM
If you use foam it has to be the 250 series which is denser & cost more than the 150 series the box stores sell. If you use Dow it's the blue, any other color is a shot in the dark. I'd find Dow blue or pay more & get it from the concrete co. The salesman at the box store will probably say his is or look at you like your nuts.
I would saw cut the top to control cracks & put 2+ coats of cure & seal while it's green.

Paul Alciatore
04-30-2013, 01:05 AM
I would not say normally around here. The mesh is laid on top of a plastic damp course membrane and is supported by whatever is handy in the way of small wooden blocks or purpose made plastic stools.

I am not really sure about the fiber reinforcement. I like steel. If I were doing it, I would go for the 6". BUT, weather 4" or 6", do NOT trust their measurement. Check it BEFORE they pour. Most 4" slabs are 3.5" at the edges and only 2" or 1.5" out in the middle where there are no reference points. But you do pay for the full four inches. They don't because the concrete is metered off the truck and they only pay for what goes into the forms. Stretch a tight string across the hole and measure in the center. I did that for the last shop slab I poured and the concrete truck driver just would not believe how much concrete went into that slab. It was only a standard 4" slab like the local building code required. Every one he delivered to must have been 2" or less. I did all the form work on that one.

The comment above about making sure the fill is completely compacted is also important. I used a sprinkler that ran for a week to settle the fill. The slab I poured did not settle even an eighth of an inch in several years.

As for steel mesh sitting at the bottom, yep that happens. I would not use wood supports as it WILL rot out and then the ground moisture will get to the steel and rust it out. It may only rust in the spots where the wood blocks were, but broken steel does not do much of a job of reinforcement. I do not know how well plastic would work or last. I like using small blocks from bricks. Break the bricks at the holes and the steel bars or mesh fits nicely in the half round slots. That sets it about an inch and a half off the ground, depending on the brick.

A 12 x 12 footer with at least two re-bars around the edges of the slab and every 12 to 16 feet across it will probably do more good for strength and durability than increasing the thickness from 4" to 6" and will use less concrete, but more steel. Be sure to overlap the re-bar at least 18-24 inches where they join and wire them together (or weld them with a shorter overlap).

flylo
04-30-2013, 01:48 AM
I agree with PaUl if all your buying is the extra concrete let them form it with 2x6 & have a 51/2"floor. Also calculate the yards or call the concrete co & you pay the concrete bill so you know you got it correct. I do it also because if they don't pay the lein goes on my house. I just priced a 40'x40' 4" w fibre graded, compacted, formed & poured 4" w/fiber, light broom finish @ $1.90 sf material & labor. It was $3.25 5 years ago.

taydin
04-30-2013, 03:24 AM
My shop is an almost square shaped 60m2. The concrete is 200mm thick, steel reinforced. It is only supported by the 4 corner walls and the underside of the concrete is empty. My mill, lathe and all the steel stock is probably close to 10.000 pounds and they are close to the shop center. Didn't see any cracks and such so far in 7 years.

One additional note: I have poured a 5mm water blocking layer, 100mm cement screed, about 10mm levelling compound, and finally tiles to the bottom. These will also count substantial additional weight, so when calculating the carrying capacity, make sure to take these into account as well.

SteveF
04-30-2013, 09:37 AM
My shop has a 6" floor, 3500 PSI, no steel, fiber reinforced on top of 2" of foam boards on top of 18" of very well compacted gravel on top of stable subsoil. No problems and no cracks except very small separation down in the control joints. With how well the base was prepared it might have been fine with 4" but I'd rather spend more money than be cursing about money I should have spent.

A couple of thoughts:

Foam boards come in different densities and designed for different applications. If you want to use some in the foundation (good idea in NC) go to the manufacturer's web site and RTFM to make sure it is rated for under slab use. I had to go to a specialty insulation supplier.

If you do use steel, make sure it is up on chairs or blocks. The concrete crew will not do an adequate job of getting it off the bottom.

Fill must be settled with physical compaction. Soil/sand gets compacted with a jumping jack tamper and gravel with a vibratory plate compactor. There are specific procedures (like gravel should be compacted in 4" lifts) that have to be followed for the base to be properly compacted. Sorry Paul, but all you did by watering your fill was make it wet.

Steve

garagemark
04-30-2013, 09:55 AM
I don't know if everyone has this issue, but I do not like fiber in concrete because it is VERY irritating to skin if you rub across it. It's just like rolling in insulation. I have a friend with it, and I won't get on a creeper anymore in his building. I'm told you can rub the floor with a brick and make it better, but it won't go away completely. Maybe fiber has improved over the older stuff, but if you will be on your back on the floor for ANYTHING, you might explore the issue further.

I have 6x6 mesh on bricks (about 2" high) in my building and a 5 1/2" pour. No problems to date.

Ian B
04-30-2013, 10:34 AM
Having read the above, I'm feeling happy with my new workshop floor. It's in a cellar, 400m2, and ground conditions were dreadful before the floor was cast. First, 80 concrete piles were driven in about 5m deep to a hard layer. Then, 17 tons of 10mm steel matting went down in 2 layers, properly spaced. Concrete was poured, resulting in an overall thickness of 14".

The cellar walls are also 14" thick, prefabricated and craned into place in 6m sections, then concrete filled. This was all necessary as the cellar floor is 2m below normal groundwater level. So far, it's completely watertight.

Ian

lakeside53
04-30-2013, 11:29 AM
I don't know if everyone has this issue, but I do not like fiber in concrete because it is VERY irritating to skin if you rub across it. It's just like rolling in insulation. I have a friend with it, and I won't get on a creeper anymore in his building. I'm told you can rub the floor with a brick and make it better, but it won't go away completely. Maybe fiber has improved over the older stuff, but if you will be on your back on the floor for ANYTHING, you might explore the issue further.



There is a couple of different fiber types - fiber glass and polyester. With polyester you simply burn off the surface with a weed-burner - it vanishes instantly. I use that for exposed aggregate surfaces. Fiberglass needs a hard-panned surface if it's going to be exposed to contact.

garagemark
04-30-2013, 01:11 PM
There is a couple of different fiber types - fiber glass and polyester. With polyester you simply burn off the surface with a weed-burner - it vanishes instantly. I use that for exposed aggregate surfaces. Fiberglass needs a hard-panned surface if it's going to be exposed to contact.

My buddy must have the glass floor. It'll turn your arms into hamburger (OK, maybe not QUITE that bad, but it is irritating). So maybe it wasn't finished correctly to begin with, or it needs another step, or coated, or something. I'm just glad it isn't my floor!

michigan doug
04-30-2013, 06:38 PM
I did my shop floor (30 x 70 feet) at 5.5 to 6" thick. 1/2" rebar both directions every 16" sitting up on plastic chairs to make sure it's the right depth in the finished floor. It's insulated with 4" of high density foam. I put a nice bed of gravel under the foam, and compacted the shyte out of it with a rented vibratory plate compactor, twice, several weeks apart. That was after driving back and forth over it with the tractor several times. Oh yeah, 4500 psi mix. Nary a crack after five years. Not even a hairline crack. I hate flimsy concrete.
It feels like you could park a tank on it, but maybe that's an exaggeration. No trouble keeping the bridgy and the grizzly 14 x 40 dead level.

My previous house had cheapo weako thin concrete floor. I hated it the whole time. Couldn't wait to move...

finest regards,

doug

Tony Ennis
04-30-2013, 08:14 PM
Having read the above, I'm feeling happy with my new workshop floor. It's in a cellar, 400m2, and ground conditions were dreadful before the floor was cast. First, 80 concrete piles were driven in about 5m deep to a hard layer. Then, 17 tons of 10mm steel matting went down in 2 layers, properly spaced. Concrete was poured, resulting in an overall thickness of 14".

The cellar walls are also 14" thick, prefabricated and craned into place in 6m sections, then concrete filled. This was all necessary as the cellar floor is 2m below normal groundwater level. So far, it's completely watertight.

Ian

So, is it a cellar shop, or a fortified underground tarmac?

lakeside53
04-30-2013, 09:00 PM
He wants it to float with a low center of gravity when the dike breaks ;)

In any case, he needs the weight - 6 feet below water table ....

darryl
04-30-2013, 09:18 PM
You guys are talking chairs, etc- supports to keep the mesh above ground. I made my own by starting with a package of plastic cups and some wire. I cut the wire into 4 or 5 inch sections, then folded each one in half leaving a bit of a loop. Poked a small hole in the bottom of the cups, then inserted the wire so the loop was inside the cup. I set up two 2x4s with a small gap between them to set the cups on so the wires could stick out downwards.

I had some holes to fill with cement, so I figured to mix up a bag, fill the holes, then fill the cups with what's left. Once you peel the cups off you end up with a wide bottomed cone shape with wires sticking out. When you have your mesh laid out, these become the chairs- you twist the wires around the mesh and there's the supports.

Rich Carlstedt
04-30-2013, 09:40 PM
5 inch thick 4500 PSI concrete, with 6 x6 =9 gage wire mesh placed on top of vis-queen vapor barrier ( 6 mil)
Have the crew hook the mesh and lift it during the pour - standard procedure here in Wisconsin .
They lift it about 2 inches, when the first pours are made, not when the leveling pours occur later.
no blocks needed.
Compacting is critical beforehand.
Most important----after the surface is leveled/trowled , and the finish can be walked on ( 3 hours?)
Wet the floor and cover the floor with plastic and keep it real wet for seven days !
Don't use the floor , except to wet it.
This long cure will double the strength of the concrete. No need for 6 bag mix, or heavy rebar and 6 inch floors

My 24 x 24 floor has no cracks period, and supports 2,000 and 4,000 pound mills
Most people are in a hurry to use the floor...don't be !
Rich

cameron
04-30-2013, 10:38 PM
Have the crew hook the mesh and lift it during the pour - standard procedure here in Wisconsin .
They lift it about 2 inches, when the first pours are made, not when the leveling pours occur later.
no blocks needed.


The second part of the standard procedure: the crew walk around in the wet concrete, step on the mesh, and push it back down.

This is not really necessary, however. Steel is denser than wet concrete and will settle down quite nicely on its own before the concrete sets.

garyhlucas
04-30-2013, 10:57 PM
Three quick concrete stories. Neighbor poured his own concrete floor and walked around half the day in regular shoes in wet concrete. Burned his feet so bad he got gangrene and nearly had both feet amputated! Watched a plumber installing a 4" PVC sewer line that was to be encased in concrete. Asked how he was going to keep it from floating. He didn't believe me, had to jackhammer up about 50 feet of it! Looked at an in ground concrete water tank 15 feet wide 10 feet deep and 300 feet long. I said "Hey you better fill that with water, if it rains it'll pop out of the ground!" He said "Wish you told me that last week, we just finished excavating under it to put it back in the ground!

becksmachine
04-30-2013, 11:47 PM
I see many references to cracks or the lack of cracks in concrete.

Now I am no expert with concrete, so somebody correct me if I am wrong, but this is my understanding.

Yes, concrete will crack due to mechanical stress, but even the best compaction and slab prep won't stop cracks due to shrinkage. And as more water is added to the mud, this increases the likelihood of cracks due to shrinkage. Consequently it behooves the owner/contractor (YOU!) to specify and monitor the slump of the poured mud.

Shrinkage is the main reason for control joints and steel reinforcement will help keep these cracks from becoming chasms.

Dave

Paul Alciatore
05-01-2013, 01:56 AM
My shop ....<snip>..... Sorry Paul, but all you did by watering your fill was make it wet.

Steve

No way. It settled over 2" over the week. It was a fine, sand like fill and very loose when spread in place. The constant water draining through it did compact it better than any mechanical process you could suggest. But it did take some time and that is probably why contractors do not use this process. Also, in South Florida where I lived at the time, the water was from my sprinkler well and only cost the electricity to run the pump.

The slab was in direct contact with the house slab which had been in place for over 20 years so it was well settled. I scratched matching lines on the two slabs and watched them. After several years there was no detectable motion. It was solid. The technique does work if enough time is spent watering it.

Paul Alciatore
05-01-2013, 02:03 AM
...<snip>...

The second part of the standard procedure: the crew walk around in the wet concrete, step on the mesh, and push it back down.

...<snip>....

Yep. I have watched it happen. They carefully lift it and then walk on it. Duuuuhhh!

And none of them has the slightest inkling of what has happened.

DO use some kind of supports that WILL support the weight of the fattest member of the pour crew. That's why I like bricks and a lot of them.

Paul Alciatore
05-01-2013, 02:09 AM
THE biggest cause of cracks in concrete is a cheap contractor who decreased the thickness to save money (for him, not for you). There are stresses and the thinner concrete cracks. Oh, and of course if the steel is omitted or also skimped on. I heard stories of whole subdivisions being built with one set of steel. Dig foundation and set up forms. Put steel in forms. Get inspection. After dark, remover steel and put it in the next foundation, next door. Pour concrete early the next morning. Get inspection of next door in afternoon. Repeat for entire subdivision.

And the money just rolls in.

And the concrete just cracks and cracks.

If you do not believe that, I have some slightly moist land for sale that I would like to show you. Only six or eight inches of water on it - in the dry season.




I see many references to cracks or the lack of cracks in concrete.

Now I am no expert with concrete, so somebody correct me if I am wrong, but this is my understanding.

Yes, concrete will crack due to mechanical stress, but even the best compaction and slab prep won't stop cracks due to shrinkage. And as more water is added to the mud, this increases the likelihood of cracks due to shrinkage. Consequently it behooves the owner/contractor (YOU!) to specify and monitor the slump of the poured mud.

Shrinkage is the main reason for control joints and steel reinforcement will help keep these cracks from becoming chasms.

Dave

garagemark
05-01-2013, 07:00 AM
You guys are talking chairs, etc- supports to keep the mesh above ground. I made my own by starting with a package of plastic cups and some wire. I cut the wire into 4 or 5 inch sections, then folded each one in half leaving a bit of a loop. Poked a small hole in the bottom of the cups, then inserted the wire so the loop was inside the cup. I set up two 2x4s with a small gap between them to set the cups on so the wires could stick out downwards.

I had some holes to fill with cement, so I figured to mix up a bag, fill the holes, then fill the cups with what's left. Once you peel the cups off you end up with a wide bottomed cone shape with wires sticking out. When you have your mesh laid out, these become the chairs- you twist the wires around the mesh and there's the supports.

Good Lord man, how long did that take?! I had a 36'x 50' slab. Broken pieces of brick here and there.... done.

vincemulhollon
05-01-2013, 08:26 AM
You may be doing a walk out, but if not

Toss some money into the stairs, I split a step hauling a very old school drill press into my basement. Didn't fall thru but it was nervewracking seeing the split wood later and realizing how close I came to a bad situation. Most stairs are built for a "fat dude" not a 500 pound press AND a fat dude and another dude helping him all on the same step. I bet we had way over a half ton on a cheapie stair step.

I painted all the walls with dry loc water blocking paint. This does NOT prevent visible leaks, like if you have water pouring out of a crack, but it does make the humidity drop practically to zero when its dry or in the winter. "Dry looking" concrete none the less pumps tons of moisture into the air. I figure in dehumidifier electricity alone, aside from comfort, the couple gallons paid for themselves in less than a season. I'm probably one of the few people who sometimes needs a humidifier in his basement...

Check your design. The good news is I have a mcmansion style utterly ridiculous "walk in" sized closet that I framed my very small shop into. So there's the den/rec/play room, then two three foot wide swinging closet doors open into a shop. Close the doors and it looks like a big clothes closet. The bad news is this means my basement stairs terminate in a wooden wall about 4 feet from the base of the stairs and there's other obstacles. I have not had issues moving small machine tools into the basement but I cannot get a couch into the rec/play room. If I had a similar sized 8 foot long lathe I'd either be screwed or really lucky depending how you look at it.

I put loud stuff like an air compressor under my stairs. The bad news is when I inevitably drop a milling machine thru the stairs it'll make a mess of the mill AND my compressor, but the good news is its much quieter than being out in the shop (assuming your stairs are "framed in". I had fireproofed foam insulation screwed into the wood, also. I went to great effort to obtain good but quiet ventilation in the semi-enclosed area. I also made a centralized vacuum cleaner system by putting the wet-dry which sounds like a small jet turbine underneath the stairs and running extension tubes thru a hole in the wall. Looks ugly but its the best hole I ever drilled in my opinion. Then I had to replace that piece of wood. I feel like drilling another hole tonight and reinstalling that! Most people are used to mind numbingly loud vacuum cleaners and its a trip to have one thats merely a calm "woosh". Where many people use compressed air to blow chips away, I vacuum them up! I have melted plastic hoses with blue hot steel chips so beware!

Best money I ever spent was after painting the white dryloc on the wall I bought those home depot type adjustable shelves, the kind with rails, bars, and wood shelves, I standardized on 12 foot wide brackets and picked random shelf lengths and stuck the rails on the wall on like 8 inch centers as I planned to load em up. Which I surely did. Obviously making all the rails line up is a job for the laser level. Anyway with 8 inch rail spacing I feel pretty confident putting "my size" of barstock on that homemade rack. I think 1 inch aluminum round is big, people who think 6 inch brass barstock is small, aside from being much richer than I, should not try this stunt. I imagine 10 feet of 8 inch brass probably weighs more than my little car and a couple hundred tapcons aren't going to hold that... or would they? Supposedly under ideal conditions in ideal concrete they're crazy strong like 2000 pounds on one little screw, but those conditions are never the case. I would never put something valuable underneath something mounted/shelved on a wall. If my bar stock collection falls off the wall it'll land on, and not destroy, my scrap metal collection, for example. If my circular saw shelf collapsed it would take out a bottle of tide detergent.

I dropped what felt like a ridiculous amount of money on lots of advanced lighting down there, and almost immediately felt glad I spent every penny. I like track lights because I can move a bulb to the perfect spot to work on a project. Its the brightest room in the house and I'm glad of it. LEDs are the way to go or you'll cook yourself down there in the summer. Yes LEDs. Remember what I wrote it was a ridiculous amount of money but I'm glad I spent every penny...

I don't know how I'd survive down there without the sink. Oh and the bar, too. And the bar fridge. And a pretty nice first aid kit that thankfully doesn't get used much. I've only got one fire escape route so I've got fire extinguishers and smoke detectors like every couple yards, seriously.

Banish extension cords to the garage. Trip and fall on concrete is not cool, and bare basements are trivial to wire real dedicated high current outlets. Speaking of wiring, never put a lamp or light bulb on the same circuit as a motor, or at least try never to do it, and never put all the lights on the same breaker. My nightmare scenario is something like a circuit breaker blows and takes out all the lights but the lathe keeps spinning in pitch blackness. That could be very awkward.

I use open top 5 gallon buckets for trash cans but never put rags with drying oils in the trash (at least until they dry..) and never put food waste in a open top trash can for bugs/rodents reasons. If vermin got in my basement they'd simply starve. Feeding them would lead to big problems.

Oh and I vacuum up all the spiders every couple weeks so my shop doesn't look like a dungeon.

And comfy chairs. My butt is in that chair for hours, my chair gets used more than any other tool in the shop, and I spent appropriately. I wish I had an aeron chair like at work but I DO have a pretty comfy executive chair or whatever its called. Those guys who sit on flipped over 5 gallon buckets for 8 hours all day in front of a $10K lathe and then complain about being sore make me laugh. I have comfy upholstered bar stools too for some tools/jobs.

I tried the rubber floor mat thing but they look awful after a couple years and the total soreness from cleaning them (and tripping on them) exceeds the small comfort to the feet. If you want comfy feet, try spending more than $15 on your shoes and skip all the floor mat stuff. I did end up tiling the floor with $1/sq cheapie tile and that makes cleanup easier than bare concrete. Also an "accident" means replace a $1 tile instead of trying to fill in a concrete divot or something. I've swept damaged worn bare concrete and I've swept cheapie floor tile and I know which I prefer.

Its the little stuff that makes the shop livable. Hey george that might make an interesting article in your magazine, the little things that make a shop livable.

SteveF
05-01-2013, 08:32 AM
No way. It settled over 2" over the week. It was a fine, sand like fill and very loose when spread in place. The constant water draining through it did compact it better than any mechanical process you could suggest. ...................

Find a civil engineer whose license depends on the soil under his project being properly compacted, and who agrees with you, and I'll send you a check for $100.

The fact that your slab didn't settle had much more to do with the fact that it was a very light building on a slab that, if you work the numbers, put less than 1 PSI load on that soil.

Proper soil compaction methods and Proctor tests and such are well established and information is easy to find.

Steve

firbikrhd1
05-01-2013, 10:03 AM
Find a civil engineer whose license depends on the soil under his project being properly compacted, and who agrees with you, and I'll send you a check for $100.

The fact that your slab didn't settle had much more to do with the fact that it was a very light building on a slab that, if you work the numbers, put less than 1 PSI load on that soil.

Proper soil compaction methods and Proctor tests and such are well established and information is easy to find.

Steve

I won't argue with anyone on proper soil compaction, I'm all for it. That said I'll pass on something I saw in S. FL recently that surprised me but is apparently an acceptable method of compacting soil.

A large lot was cleared and filled, about an acre or so, and a dike built around it about 18" high. Then water was pumped into the diked area for a period of a few of months, the diked area continually kept filled with water about a foot deep. Afterward the dike was removed and the lot considered ready for construction.

I'm not promoting this idea, nor defending it. I'm simply reporting what I saw. Whether this is a newer low cost method of compaction or not I can't say.

vincemulhollon
05-01-2013, 12:49 PM
Maybe they wanted to see if the sinkhole underneath the lot could support the weight of a house? Or a septic tank perc test gone horribly wrong?

1-800miner
05-01-2013, 05:29 PM
In the area where my mill and lathe were going to go I used a post hole digger and drilled holes where
I thought the corners of the machinery would be. Eight inch diameter and three feet deep.
Cased the holes with sona tube and placed 90 degree bent rebar down the holes and tied to the main mat.

It cost me an extra yard of mud and a couple of bucks in extra rebar. But I know those two machines are solid in the ground.

Peter S
05-01-2013, 08:08 PM
According to my industry guide book (BRANZ), slab reinforcing must be in the top half of the slab, but with a minimum cover of 30mm. So for a 100mm thick slab the reinforcing will be withing 30-40mm of the surface.

I am surprised by the drama about mesh. Get some plastic chairs, they are made specifically for holding mesh at the right height, they are cheap and do the job perfectly. There are several height ranges, the type I use each have two height options per chair. They are placed about 1 metre apart, no tying required and you can walk or barrow concrete on the mesh, no problem.

I am waiting for driveway concrete at present, here is a chair with height options of 75 and 90mm, concrete will be about 125mm thick.

http://img.photobucket.com/albums/1003/PeterS/chair75-90_zpsc3e77a10.jpg (http://smg.photobucket.com/user/PeterS/media/chair75-90_zpsc3e77a10.jpg.html)

Re. watering hard fill. My guide recommends keeping the hardfill wet while you are compacting, this gives better density.

Threads like this are of dubious value IMO.....

Paul Alciatore
05-01-2013, 11:06 PM
Steve,

Save your $100. I never said it was acceptable for a skyscraper or other commercial building. It was a single story, CBS structure (concrete block, stucco). The fact that it did not settle, at all, shows that the method was probably sufficient for the purpose. The local building code and the building inspectors, who I DID consult on the project, did not require even that much. The only comment he made was that I needed to completely clear off the existing grass before the fill was added to the site. That was to prevent settling after that grass decomposed.

Again, it may not be sufficient in all areas or with all types of fill. I guess my real point is that any added fill or disturbed soil does need to be compacted by some EFFECTIVE means. Do check with your local codes and talk to the inspectors. They have a pretty good knowledge of local conditions and of what works and does not work. I have found the ones that I have worked with, in more than one state, were very helpful.




Find a civil engineer whose license depends on the soil under his project being properly compacted, and who agrees with you, and I'll send you a check for $100.

The fact that your slab didn't settle had much more to do with the fact that it was a very light building on a slab that, if you work the numbers, put less than 1 PSI load on that soil.

Proper soil compaction methods and Proctor tests and such are well established and information is easy to find.

Steve

dian
05-02-2013, 07:18 AM
very weird reading all this. i have not seen any new built house over here with a concrete slab of less than 10". rebar goes in in two layers and is spaced 1" from top and bottom. the slab in my house is 13".

jep24601
05-02-2013, 10:19 PM
Civil/Structural Engineer here. The only way to compact sand is to flood it (have a standing water level above the level of the sand). It is a lot more dificult to do than it sounds on account of the serious volume of water needed when dealing with an area of ground. This only applies to sand. "Jetting" of clay fill as practised by our local sewer district is a total joke.

jep24601
05-02-2013, 10:22 PM
very weird reading all this. i have not seen any new built house over here with a concrete slab of less than 10". rebar goes in in two layers and is spaced 1" from top and bottom. the slab in my house is 13".

It is the same in the US where a slab foundation is used - usually post-tensioned.

jep24601
05-02-2013, 10:32 PM
5 inch thick 4500 PSI concrete, with 6 x6 =9 gage wire mesh placed on top of vis-queen vapor barrier ( 6 mil)
Have the crew hook the mesh and lift it during the pour - standard procedure here in Wisconsin .
They lift it about 2 inches, when the first pours are made, not when the leveling pours occur later.
no blocks needed.
Compacting is critical beforehand.
Most important----after the surface is leveled/trowled , and the finish can be walked on ( 3 hours?)
Wet the floor and cover the floor with plastic and keep it real wet for seven days !
Don't use the floor , except to wet it.
This long cure will double the strength of the concrete. No need for 6 bag mix, or heavy rebar and 6 inch floors

My 24 x 24 floor has no cracks period, and supports 2,000 and 4,000 pound mills
Most people are in a hurry to use the floor...don't be !
Rich
Best advice in the whole thread except for "hooking" the reinforcement which is not an approved practice (and doesn't work but saves contractors a lot of money)

Fiber reinforcement is good for impact resistance. Claims of the ability to resist cacking vary. When I asked a fiber manfacturer how much further apart I could space the crack control joints he said I had to space them the same as if I had no fiber.

GEP
05-03-2013, 08:36 AM
What makes concrete strong is the amount of cement in it. I would never poor concrete unless there are 6 bags of cement per yard and at least a 1 foot sand base under it and steel rod if you park a tank on it. Fiberglass fiber concrete was to be used for exterior only. fiber will not allow you to trowel it and make it nice and smooth. A home shop floor with a 6 bag concrete mix 4" thick floor will support all the weight you need. If you happened to run a heavy CNC machine a extra heavy footing is recommended with a stone base and concrete on top separated from the shop floor to stop vibration transfer

dneufell
05-03-2013, 07:45 PM
"10" Logan lathe, a 12" Vernon Shaper, an Index Model 40 mill to start"

No one knows what future holds. When I built my garage I figured some day to have a mill and lathe. Concrete was cheap in those days. I tend to overbuild. Here i am now with 5 cnc lathes, 4 manual lathes, Bridgeport and a full size machining center. I looked at it as how hard is it to redo something after is plucked up from just doing the minimum the first time. :) Dean

Rich Carlstedt
05-03-2013, 08:46 PM
Surprised that no one here, other than jep24601 is aware of the cheapest and easiest way to get free concrete.
I was made aware of this 50 years ago, working in construction
As said earlier, 'keep the concrete wet for 7 days" and you will double the strength.
SO your 4 inch floor will have the strength of a 6 + inch floor ...simple yet, not known apparently.
Why pay for 6 inch floors when you can have a 4 that is equal in strength ?

here is a link
http://www.concretenetwork.com/concrete/slabs/watercure.htm

Not only does it work, you eliminate cracks as well
The State built a concrete overpass near me and they kept the concrete wet for 3 +weeks. I know , as my car got wet everyday going under the bridge, after the work was done and the road under where I drive was opened ( but not above !) . Finally about a month later, the fire hydrant was shut off

My 24x 24 shop floor is flat and smooth, and has no "expansion grooves" in it . It is 23 years old and no cracks !
A perfect slab !
Rich

jep24601
05-03-2013, 09:23 PM
A few years ago some research found that if you keep new concrete wet for 28 days you will considerably reduce the porosity of the concrete - a major factor where highway bridges are concerned. The majority of the strength is gained with 7 days of wet curing though I have never seen the need to keep passenger cars off driveways for more than a couple of days since it usually has enough strength to allow light use after that time (still being kept wet)

Concrete sets by a chemical reaction between the water and the various complex compounds which constitute cement. Let it dry and you remove one of the chemical constituents and you halt the chemical reaction converting the constituents into hardened concrete. Concrete does not harden by drying.

jep24601
05-03-2013, 09:35 PM
The OP does not say what kind of soil he intends to build on. Here in St. Louis on firm clay 4" of compacted rock with a 4" slab might be perfectly adequate but a few miles away in an area of plastic clay (which has a shrink and swell susceptibility with variations in moisture content) it might be necessary to go with 4' of rock (yes- 4 feet!).

In the residential market it is difficult to get any material compacted properly unless you do it yourself so for deeper bases it is safer to use clean rock which is self compacting (like marbles in a jar) but vehicles can't operate on it (cos it's like marbles) but if the surface is choked off with fines then it is good to work off for foot traffic and rebar chairs. However with a deep base of clean rock you can get soil washout into it causing a hole in your yard or driveway if it is not well graded away.

firbikrhd1
05-03-2013, 10:10 PM
Update:
First, thanks to all who have responded with advice and experiences. I still haven't made a final decision but I have enlisted the advice of a geotechnical engineer. He has tested the soil, we have spoken about fiber reinforced concrete, wire mesh reinforcement, etc. Based upon his advice at this time I have decided to use 4" heavy gauge wire mesh flats in the shop area and I will place it on concrete bricks so it cannot be mashed into the dirt by workers. If I place the bricks a couple of feet apart the wire should be of sufficient strength to support the weight of the finishers, much like a trampoline. The concrete will be 3500# mix 6" thick. According to my engineer, the use of 4500# and above concrete can be a cause for cracks because it doesn't flex under load as much as concrete of lower strength. In other words a little flex will prevent cracking where the super hard stuff is more brittle. The slab will be poured on a compacted crushed stone base with vapor barrier, stone thickness as determined by the engineer. This guy builds dams for a living so I trust his expertise.
He also echos what others have said; if concrete wants to crack it will crack. It may be due to shrinkage or other cause. Most cracks develop at outside corners, but can occur anywhere, regardless of thickness, reinforcement, stable base soil, expansion joint location, pretty much no matter what.
I haven't yet decided on whether I will use fiber reinforced concrete or not. My engineer isn't a big fan of it and prefers steel or mesh while my contractor who has about 35 years experience and is working on a fee basis (he doesn't make a dime more or less no matter which I choose) has had excellent results with the fiber reinforced stuff. He has offered to show me several of his completed slabs that have had some age and wear on them before I decide. I am concerned about smoothness of finish and whether it will be too abrasive. I do my own automotive work and don't care to feel like I've been rubbed raw after a day of lying on the garage floor. Part of the contractor's job is to see that the building comes in within budget, or close, so no doubt he sees fiber reinforced concrete as a cost saver. That's fine as long as it will do the job required.
Ultimately, I'll probably go with the engineer's advice but if the fiber reinforced stuff looks good I may use it in lieu of steel in the remaining areas of the basement which won't receive the heavier loading.

valleyboy101
05-03-2013, 11:11 PM
One thing to make sure of.
Cut the concrete in a grid pattern about a day after it is poured. I cut mine in a 12 - 15' grid and after 6 years no cracks or water seeping up. I used clear crushed stone in the basement and compacted gravel in the garage.
Michael

oxford
05-03-2013, 11:40 PM
I didn't read every reply so maybe someone mentioned this. My father told me a story of when they repoured some floors where he worked with fiberglass reinforced concrete. He said people were bothered by it with fibers coming out and getting airborne. They eventually ended up tearing it up and re-doing it. I have no direct experience with this, so maybe someone with more experience can comment on this.

GEP
05-04-2013, 06:43 AM
Oxford
I believe of what you are saying. Fiber concrete was only to be used outside. I did forget to mention earlier , i always kept concrete wet for as long as i could.

oxford
05-04-2013, 09:41 AM
^^^Maybe. It could have been the contractors that did it didn't know what they were doing or maybe it was done in the early days before it was perfected. I just remember him saying a lot of guys were getting irritated from it. I don't know if it was there skin, throats or both. It may also have been from forklift use over it.

I would like to hear if anyone else has ever heard or experienced this. I know if I was ever going to have a new floor poured and they were wanting to put it in I would be doing a lot of question asking.

The Artful Bodger
05-04-2013, 04:14 PM
We had a house built two years ago, 200 sq metre concrete slab, steel mesh, plastic vapour barrier all on top of 200' of well settled gravel. We had a pretty nasty earthquake (much of a city destroyed) two days after the slab was poured and I fully expected cracks to appear because of it but no signs as yet.

flylo
05-04-2013, 04:53 PM
That's another reason to use a vapor barrier & cure-n-seal. it holds the moisture in so it cures slower. I'm sure not as good as keeping it wet for 28 days. As far as fiber they use a different one now that doesn't irritate & finishes well. I'm sure they have several fibers for different apps.

The Artful Bodger
05-04-2013, 04:57 PM
We were offer steel 'nails' as reinforcing but the contractor had not had experience of them and was not keen so we stuck with the steel mesh. He did say they are not to be used on exposed concrete floors as they could produce rust spots.

firbikrhd1
05-04-2013, 09:02 PM
That's another reason to use a vapor barrier & cure-n-seal. it holds the moisture in so it cures slower. I'm sure not as good as keeping it wet for 28 days. As far as fiber they use a different one now that doesn't irritate & finishes well. I'm sure they have several fibers for different apps.

Flylo, can you tell me more about the fibers that don't irritate or your experiences with them? From what I have learned there are steel fibers, fiberglass fibers and polyester fibers, each with strengths and weaknesses. Although I have not personally seen any examples of any finishes yet, I am told and have read that with fibers (other than steel) you cannot expect to end up with as smooth a finish as with conventional concrete and may have a "fuzzy" floor due to wear or finishing technique.
I certainly wish I had the straight dope on these points. I certainly don't want a floor that is irritating, fuzzy or rough. As of now I am leaning towards conventional concrete with steel mesh reinforcement. That seems to be the least risky, time proven method.

flylo
05-04-2013, 09:42 PM
I think on mine they used poly fiber then power troweled it & it finished very smooth, much nicer than when fiber 1st came out which I think was FG. I can call the concrete co monday & verify it. I know it has fiber because I paid the concrete bill. I'll verify it monday.
Also I had an 8000# lathe sitting right next to a saw cut, a 14,000 forklift next to that & no visable cracks but I was concerned.

firbikrhd1
05-04-2013, 10:07 PM
Thank you Flylo, I'll watch for your Monday update. I certainly appreciate your help with getting the info.

GEP
05-05-2013, 07:40 AM
Here is a link that will explain fiber. I never used fiber on my work in 35 some years
http://courses.washington.edu/cm425/frc.pdf

jep24601
05-05-2013, 09:21 AM
I have specified polymer fibers in concrete where impact damage might be likely but have not designed with it for strength purposes. In sufficient amounts it will help against shrinkage cracking. If it is to be used as an alternate to steel bar reinforcement the literature suggests
apppropriate steel fibers at a dosage rate of 40 kg per cubic meter. It is suggested that a thinner slab of equal strength can be achieved. That makes sense because the concrete beyond the rebar in a bonded bar system plays no part in the bending strength of the slab where the steel fiber system, with the fibers all through the slab, would be effective for the full depth of the slab.

Personally I would go for a really well compacted base, steel mesh reinforcement properly supported, and a 7 day wet cure followed by chemical sealer such as V-Seal applied to the damp concrete.

flylo
05-05-2013, 10:56 AM
I found this from the UK. I think this is the type they used on mine but will still check. Thanks! http://cemexliterature.co.uk/pdf/Concrete_1_DS_Poly_Fibre.pdf

257
05-06-2013, 01:54 AM
i did the prep myself 6 inch floor 8 inch on the outside 4 feet 1/2 inch rebar and fiberglass in concrete. 4 years no cracks no problems there is 8 inchs of crushed limestone for a base

darryl
05-06-2013, 03:52 AM
Bit of an aside- what might be the norm for the edge of a slab where your vehicles would be driven onto it? The slab would be at the same height of the approach, which would either be compacted gravel, or topped with asphalt. I'm thinking that the edge of the slab might be thicker and have some re-bar in it. What might be some good numbers here? I'm thinking the slab would be about 5 inches thick, with 4 or 6 inch mesh in it, but the edge where you'd drive vehicles onto it might be 8 or 10 inches thick, for perhaps 12 inches or so, and have some re-bar in it also.

I suppose this is typical of a commercial garage, where a paved surface butts up to the edge of the concrete floor of the shop. I'm supposing that there's a minimum requirement or a standard for the construction of the slab where a large door would open and vehicles driven in.

jep24601
05-06-2013, 08:19 AM
Bit of an aside- what might be the norm for the edge of a slab where your vehicles would be driven onto it? .

I would put a footing under that edge of the slab.

flylo
05-06-2013, 10:11 AM
Just called my concrete co & yes it is poly fiber & he said when you power trowel it the fibers get pushed under the surface so you get a good finish. I guess like the stone gets pushed under the surface when you bull float. Good Luck!

lakeside53
05-06-2013, 11:37 AM
And if it stick ups (it does with exposed aggregate) you just take a weed burner and make a quick pass. Gone instantly.

jep24601
05-06-2013, 01:15 PM
Keep in mind that the polymer fiber manufacturers DO NOT claim that it takes the place of steel reinforcement.

flylo
05-06-2013, 02:19 PM
If you want the very best 6" floor money can buy why not use mesh, rod & fiber? Each has it's own advantages. I know I worried when the heavy leg of the 8000# lathe sat 2" inches away from a cut joint, actually near the intersection of 2 cuts for a year & 1/2 & the forklift on the other side, but all was well. I had a base of crushed concrete & sand over that.

firbikrhd1
05-06-2013, 11:00 PM
Thank you to all who who have responded and Flylo, thank you for taking the extra time to speak with your concrete company.
Today I went to a house under construction and looked at a garage floor my contractor has done using FRC. I gotta say, the finish was excellent. No fibers of fuzzyness. My contractor tells me that sometimes there is a bit of a fuzzy surface but it wears away very quickly with use. No doubt a torch would cure the problem as well.
As of now I believe I will use 6" of FRC with 4 X 4 wire reinforcement in the shop floor & garage floor. The remainder of the basement will only use FRC. The front edge of the garage floor will have a total of 24" thickness of concrete, including the footer and steel from the footer will be bent horizontally into the slab and extend into the slab about 2 feet from the edge. Given the floor will be 6" thick FRC will likely be as good as 6 X 6 welded wire mesh and much better than the same mashed into the dirt by indifferent workers.