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OT: Replacing a beam supporting concrete block wall?

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  • OT: Replacing a beam supporting concrete block wall?

    I recently purchased a concrete block building made in the 1950's. There is about a 12'-14' section above some windows and doors where the concrete blocks are sitting on top of an old wooden beam/header. There are probably 5 rows of blocks on top, and then more modern construction has been framed on top of those when a second story was added. There is load bearing framing helping to support the beam here and there with the longest span being about 7'.

    This would be years down the road and I would very likely hire it out but what sorts of techniques might be used to replace that old wooden beam? How would someone support the concrete blocks to change the beam? Curious minds want to know!


  • #2
    Precast concrete lintels, sized accordingly. I would support the load above the rows of concrete block, and then just take out the wooden beam. The blocks will support themselves just fine in a 7' span as long as they are in good condition. Then install lintel and pack cement joint between old block and new lintel.
    Last edited by polaraligned; 12-04-2016, 05:27 PM.


    • #3
      Generally acrow or screw supports and strongboys are the order of the day, however it can be done with a length of angle bolted to each block, there are commercial ones available, I'd go with acrow props myself as the last time I used the angle method the span was much less.
      Getting cement mortar in is difficult as a continuous bed is needed so lay a bed on top of 5:1 sand cement or 4:1 as you like, wettish mix in a prism on the top of the Lintol and squeeze it up with the props, if you can't squeeze I've found the old slate shim method is OK although I recently substituted UHMW poly, worked fine.
      Just make sure you don't drop a wall on your head!, don't laugh I've seen it happen!
      6"x4" reinforced concrete or prestressed , minimum wall bearing 6", aim 10-12"
      Last edited by boslab; 12-04-2016, 06:49 PM.


      • #4
        Okay, that all makes sense. I didn't understand how that would work but now I see temporary support it provided by acrows and strongboys. Thanks!


        • #5
          Don't know if there's a way to tell, but there could (should) be some rebar in there above the wood beam. I'd check to see if the beam is actually carrying any weight- there's a good chance there will be a gap there by now if it isn't. You can probably remove the beam and either replace it or put something else in its place without needing to support anything.
          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


          • #6
            My area was built in the 1930s, brick. In these houses, above windows, and any non-arched door is a steel beam across. There are a couple houses built much later, in the 1950s, and they have the same steel beam over doors and windows.

            A wood beam seems a weak substitute, especially for wider spans. Are you sure there is no other beam that is hidden by the wood?

            Keep eye on ball.
            Hashim Khan


            • #7
              Just in case some others here have never heard the term acrow, I did a search. I went through about five or six on-line dictionaries with no luck. Finally Wikipedia had it:


              Even had a picture.
              Paul A.
              SE Texas

              Make it fit.
              You can't win and there is a penalty for trying!


              • #8
                I remember seeing a bunch of those in a home on Holme on Homes (or something like that), where a guy had been hired to install/improve the furnace ducting of a home, and because the basement where he was running the ducting didn't have a lot of headroom, he figured he would maximize the available headroom by cutting space for the duct in EVERY SINGLE joist. Afterwards, the entire house sagged down and the guy just walked away from the project. They used a bunch of those acrow thingamabobs to hold the place up temporarily. I forget if they figured out a way to replace/support the joists or if the house had to be rebuilt.


                • #9
                  Acrows are used extensively over here, I carry one in my van permanently. I would not rely on a 7 foot span of blockwork to self-support - it might be perfectly fine but even if it doesn't collapse it will likely suffer loss of integrity.

                  I would suggest using strongboy tops on acrows to support the blockwork temporarily whilst you replace the joist. If you can't buy them, make some. The design of strongboys and acrows is very basic. A cheap bottle jack under a tube, packed up to height would suffice.

                  Peter - novice home machinist, modern motorcycle enthusiast.

                  Denford Viceroy 280 Synchro (11 x 24)
                  Herbert 0V adapted to R8 by 'Sir John'.
                  Monarch 10EE 1942


                  • #10
                    We call them steel lintels & sizing depends on the roof load, span & code requirements. I've never seen wood ones & live in an a 1880s home. I have seen flitch beams which you may have which is a steel plate with lumber on each side & all bolted thru.
                    "Let me recommend the best medicine in the
                    world: a long journey, at a mild season, through a pleasant
                    country, in easy stages."
                    ~ James Madison


                    • #11
                      You could lag or all thread a heavy angle iron to the block covering the span. Both sides being better. The angle would face out. Support the angle iron with jack posts and remove wooden beam.


                      • #12
                        I suppose it depends what you want to have under that beam in the future, but are the five rows of block worth saving? They seem obsolete. You could just reframe the entire opening (all the way up to the newer frame construction) to accommodate whatever you really want there. We have a number of block buildings around here and the long shallow spans like that always look kind of pointless to me.


                        • #13
                          I'm with AntonLargiader, get rid of the blocks. I once saw someone (an idiot, but whatever) try to
                          remove the wall separating two tenant spaces in a brick building. What he would have ended up with was the brick parapet wall above the roof, about 4' high balanced on a flange beam. fortunately he dropped the whole mess while trying it. Somehow he escaped a Darwin award.

                          I'm picturing a section of the wall you are working on. A flange beam with a few inches of bearing on each end, a 4 block high wall balanced on it, a stud wall above that. That's three potential places for the assembly to hinge and kick out sideways.

                          A simple temporary stud wall just inside of your work area could support the floor above if the second floor joists are perpendicular to it. Would make a simple job.


                          • #14
                            GKman, sounds like you are talking about a townhouse style firewall, they're supposed to extend above the roof to prevent a fire from spreading to other units. In many places removing them also removes the occupancy permit.

                            What I've done before to create or repair doorways is to chisel out the mortar above the (planned) beam and a couple feet into the side walls, then install wide angle on each side to support the span. Then remove and replace whatever was holding it up.
                            Some openings I've worked on have been supported by hidden beams, either an inverted T or a square channel set into the lowest row of blocks, sometimes an I beam and cut blocks on both sides. anything below that is either cosmetic or merely to frame the door/window.
                            I'd try to drill into the beam and see if you hit steel


                            • #15
                              Originally posted by kendall View Post
                              GKman, sounds like you are talking about a townhouse style firewall, they're supposed to extend above the roof to prevent a fire from spreading to other units. In many places removing them also removes the occupancy permit.
                              If the guy was ripping out the block wall under it, I think the deed was done no matter what happened to the parapet wall.

                              Doorways are one thing, but a 20' span that is only 5 blocks high is totally another. Preserving the integrity of the mortar joints seems nearly impossible, and for what?