Building Homes or Extensions/How to install a beam in a large hole cut through a solid brick wall
Similar to a recent project you replied to, I have a situation where I need to cut a hole in a solid brick wall. This hole centers around an existing 3 foot door that needs widened to 16'w x 9'h. Although the wall separates interior spaces, it is an exterior wall above the first floor roof, as it separates a one story portion from a two story portion, and is the original exterior wall with the one story side being a later addition.
The building is a two story Georgian. The height of the existing brick(load)above the new beam supporting the loads is approximately 10', I figure 1200 per ft uniform load of brick, add another 1500 per ft. for existing wood lathe, roof, floor, plaster, etc. loads, were close to 3000 per ft. The brick wall thickness has not been verified I assume 12".
What is a good way to hold up the house above until the steel beam/s are installed, or how best to install a multiple member piece using something similar to your steel angle method prior to demolition?
Should the compressive strength of the antique mortar that remains on either side of the new opening be relied upon? I plan on using steel columns either side to support the steel beam and/or multiple steel elements of some sort in some way. The flange thickness will likely exceed mortar joint width. I think steel angles will be too small for this situation.
New foundations cut into the old wall below grade and under the posts will need to be figured out I can't rely on the old mortar to support the loads.
Base everything on 12", but if you think about it while replying, if I find the wall to be 8" or 17", how might the solution be affected other than steel size?
Thanks for your input.
Hi Roderick, when you were a kid did you ever pick up three blocks with one in the middle being held by pressure from the blocks on each side? As long as you had side pressure the middle block remain suspended between the two outside blocks but the second you relaxed your side pressure the middle block fell. A masonry/brick wall is similar in nature. As long as you have enough mass on each side of an opening it is extremely hard for the middle of the opening to collapse because in order for the middle to come down the sides have to give way much the same as the blocks we played with as kids. The brick in your wall are held in place by friction.
Now that's not to say the center of your opening won't collapse if it goes through enough trauma that the mortar between the bricks crumbles releasing the friction bond between them. That being said you probably can use an angle on each side(inside and outside) of the wall to support this opening while removing the brick provided it is big enough. A 5"X5"x3/8" angle slipped into a saw cut that creates at least 8" of bearing on each side (left and right) of your new opening would probably suffice. Ideally you would make the location of these angles high enough in the wall that after the demolition you can then slip a steel beam and end posts underneath the angles for your final support. The new beam can then be tack welded to the angles to hold the entire assembly in place.
Another option would be to use angles with a longer up leg like 8" with holes drilled every 16" and through bolt the two opposing angles together with 3/4" bolts and then all you would need would be structural supports at each side of the opening as you mentioned in your query.
I have no way of knowing what condition the mortar or structural integrity of the existing wall is so I can only suggest that you have an engineer look at your project to verify my suggestions.
Sincerely Bruce Johnson, bejohnsonconsulting.com