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  • New opening in an existing CMU wall

    I need to put 2 new openings in existing interior CMU walls. One wall already has an opening, but the lintel is at 6'-8" and we need to raise it.

    I understand that in the new opening I have a couple choices with cutting the mortar, inserting angles on both sides and then removing the blocks below.

    Where there is already a lintel, do I need to do the same, but have the angles be supported 6" beyond the existing lintel? Is there an easier option? Or an option where the steel is not exposed? The walls are inside an athletic center with a pool in the next room so moisture will be an issue.

    Attached are a few options I found on the internet.
    Attached Files

  • #2
    Re: New opening in an existing CMU wall

    Your talking about a commercial building. What you found, may work in one state and be legal to do, code wise. But code in your state may not find a certain method legal. Consult your building inspector of your options when you go to get the permit to do the work.
    Great Link for a Construction Owner/Tradesmen, and just say Garager sent you....

    http://www.contractorspub.com

    A good climbing rope will last you 3 to 5 years, a bad climbing rope will last you a life time !!!

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    • #3
      Re: New opening in an existing CMU wall

      Thank you. I'll search through the codes.

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      • #4
        Re: New opening in an existing CMU wall

        Precast lintels are available in some areas. It is common in Florida where masonery construction is more common to use precast lintels for all "outside" openings (doors and windows). These are all for 8" block construction. I don't know if they are available in lessor thickness or not??

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        • #5
          Re: New opening in an existing CMU wall

          What is the width of the new opening(s)?

          Have you thought about inserting the temp lintel as you describe a couple courses above the opening and installing a precast lintel (depending on the opening size you may need a WF beam faced with 4" CMUs), then rebuild the wall up to the bottom of the construction aid which can then be removed once the wall has set up for a few days. Then go back and tuck fill the saw cut joints used for the construction aid.

          I did a similar job installing a small (6-0W x 7-8H) roll up door in an exterior wall, and that in a nutshell is how we handled it. We used two pieces of 4x6x3/8" angle with the 4" leg inserted in the joint and the 6" leg vertical above. The two angles were through bolted with 1/2" rod to one another. Angle length if I remember was two full CMUs longer than the new opening, but you need to size everything depending on your particular situation. Is the CMU cores empty or filled with mortar?

          There are a number of variables that you as an Architect should be able to answer or should know to take to an structural engineer. We had to show sealed drawings of how the work would be accomplished as the building was still occupied during remodeling. This is a grat forum with loads of useful information but this internet engineering is not one of our specialities.

          Remember the Kansas City Hyatt Regency disaster? How's your E&O insurance
          Last edited by Bob D.; 01-24-2009, 01:04 AM.
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          • #6
            Re: New opening in an existing CMU wall

            This is exactly why I'm concerned. I have no way of knowing how the wall was constructed until they open it up. Neither wall is load bearing but I don't feel I know enough information about the wall construction to move forward.

            The company I work for is the 'owner' and the 'contractor' for all small jobs on the campus. It seems everyone including the BI seems to think this is a quick, easy job and that the wall will hold itself up during the demo. That very well may happen, but I would like to prevent any minor collapse by providing temporary support.

            Thank you for the response. The new openings are 40"w x 88"h openings. I am 90% sure that the existing lintel is a W beam faced w/ 4" CMUs - I need min. 4" bearing on either side by the MA code. The contractor wants 12" on either side to be safe. I agree. I agree with the temporary lintel being a few courses above as well.

            The BI is not requiring that I stamp these drawings either. I would think they would want that, but they are not concerned. I think sometimes too much info. is left off drawings in expectation of the contractor knowing sound building techniques. This can be dangerous as you show in the link to the Hyatt disaster. I am covered for insurance, but would not want any collapse on my shoulders for many reasons. The guilt I should probably lay on my shoulders is having the company pay extra $ for an engineer to look at it.

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            • #7
              Re: New opening in an existing CMU wall

              Originally posted by engineer View Post
              Precast lintels are available in some areas. It is common in Florida where masonry construction is more common to use precast lintels for all "outside" openings (doors and windows). These are all for 8" block construction. I don't know if they are available in lessor thickness or not??
              We can get precast lintels in MA. The wall is an 8" wall. I will look into which will be better, but the existing has a W beam, so I feel I should go with what is existing. I may be able to reuse it for the one of the openings if it is in sound structural condition.

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              • #8
                Re: New opening in an existing CMU wall

                Well, I guess I don't have much to worry about since this was a drawing for a previous alteration to the same existing building. (see attachment) I guess my 40" wide openings in non-load bearing walls don't quite compare...
                Attached Files

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