My house is a 1970’s cement-block structure (single story). I want to cut a new window into an exterior wall, which is load bearing. Do I need to put a header above the opening. And if so, what type do you recommend? I have never worked with block houses, so please be detailed with your suggestions.
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I believe the standard technique is to cut a slot, and install a steel angle lintel.
Then remove blocks below.
Thanks. Do you have any additional suggestions?
Depending upon the height of the window relative to the top of the wall, it might be easier to remove all of the block above, and build a wood or metal header to support the roof. Just would have to consider how to handle the aesthetics of applying trim to the window top on the outside.
Another technique is to install a concrete header. They can be purchased prefab, or made in place. Either looks better than steel.
Unless you have unusual loading or a very wide window, the header should bear at least 8" on either side of the opening.
To form one in place you temporarily support the load above and take out two courses above the opening. Build temporary wooden support and lay one course of lintel block. Then put about three pieces of rebar in the block and fill it up solid with concrete (suspending the rebar in the concrete, of course). When the concrete has set, fill in the course above with ordinary block. A cast in place lintel is also sometimes called a bond beam.