Question about 'lateral support' needed for a center beam
This is actually not for a brownstone, it’s only a 1.5 storey home, about 30Lx25W footprint. It’s connected to another building (same address) with no foundation wall in between them.
The center beam spans 25 feet. On one end it’s supported by a post of four 2x8s (about 5′ high, with a concrete pier below them) bound together with several very large bolts. Then there is a load-bearing 2×4 stud wall running perpindicular to the beam about 3 feet later, then a concrete-filled lally column about 6 feet after that, then a 4×4 post (that is itself bolted to a perpendicular stud wall) about 3 feet after that, at which point there is about 5 feet unsupported beam before resting on the foundation. May sound strange but looks normal in context. The reason for the extra support (e.g. the 4×4) is that the beam is not 100% straight (titled/twisted maybe about 5 degrees) and underwent a very slight twisting at some point in the last 5-10 years (possibly much longer; not known). It has not apparently changed in the last 4 years. There are two sections of load bearing walls on either side of the beam, roughly at the halfway point towards the foundation, so not sure if the beam is even needed at this point. I believe the twist was caused partially by the bowing out of the outer walls of the home (due to excessively small rafters and a third layer of roofing added on about 7 years ago). This issue has been solved by slightly jacking the roof out and sistering-on oversized rafters. The floor joists are I believe 2x10s, possibly 2×8, with many pieces of ‘blocking’ between them.
The current plan is to cut out a fairly large basement window in the foundation wall directly next to the center beam (about 3-4 inches away), which will involve cutting about 2 feet down and about 3 feet across. So the center beam will continue to have vertical post support from the concrete foundation wall, but will not have anything next to it on one side going down two feet.
**My question is, is the vertical ‘post’ support provided by the foundation wall the only real consideration, or in normal circumstances can the adjacent portions of the wall come into play in support for a center beam?** (We had one very minor earthquake about 10 years ago that destroyed no buildings I know of, and that’s the only one I’m aware of in last 30+ years.)
As potential overkill (?), we’re considering adding another lally column just before the foundation wall (with a piece of thick angle iron bolted on to help prevent any further twisting), so that less weight is potentially resting on foundation. We may be overthinking this – which is what a contractor I showed it to (not necessarily guy doing job) seemed to think, and scoffed that there was an issue with cutting for the window – just thought would ask for any input.
neelazermi
in General Discussion 4 years and 6 months ago
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neelazermi | 4 years and 6 months ago
OK will check back here afterwards; thanks again
restorationcontractor | 4 years and 6 months ago
I would be interested in hearing about what your engineer came up with.
neelazermi | 4 years and 6 months ago
Thanks a lot for the detailed tips. I will get in touch with an engineer for a basic consultation, then go from there.
restorationcontractor | 4 years and 6 months ago
As far as securing the carrying beam to the foundation wall It’s a relatively simple custom steel fabrication, there are various ways to do it.
You can’t do the bolt you suggested, and the I beam is not necessary. You just want to anchor the end of the beam to the wall.
One way to do it would be a flat steel plate anchored to the block using the Hilti epoxy system with epoxy screens and threaded studs, nuts are tightened after the epoxy is set. Plate would be fabricated with flat bar or angle pre drilled and welded perpendicularly to the plate at the top. Carrying beam is then drilled and through bolted at its end.
You may also need to add a bearing plate under the beam.
You may need to grout (fill) the upper courses of block for the bearing plate.
To be clear this is one potential solution based on my understanding of your description without seeing the actual field conditions.
You really need to have a structural engineer look at this and the other issues you describe.
hkapstein | 4 years and 6 months ago
If it’s not clear, why not have an engineer look at it? There may be other issues with this plan you’re not thinking about, or better solutions than you’ve come up with. The money spent on an engineer may even save you money as contractors tend to overkill when they design structures.
neelazermi | 4 years and 6 months ago
Also should mention, thought foundation wall was poured concrete but it’s actually masonry block
neelazermi | 4 years and 6 months ago
Yes my understanding of the carrying beam (6×10 beam, likely 80-90 years old) is just to hold up the floor joists over the 30-foot span that would otherwise be too much, and hold up everything resting on them (whole rest of house). There are many walls in different directions on the first floor above basement, so lot of load-bearing happening there. Originally it was just a 1-storey home with a fairly high-pitched attic, which was later finished in the 1970s, but the structure remained the same. The load-bearing walls I described are actually in the basement, where a network of rooms was added (office space). I should have clarified when mentioning them – they’re load-bearing in the sense that they are currently bearing a [potential, maybe not actual] load, where previously the space was open and the beam and foundation were doing all the work – but not structurally load bearing in terms of the original design. That said, since the greatest space between said interior stud walls in basement is only about 8-9 feet at any given point, the beam may or may not even be needed , or needed nearly as much.
Based on some other workmanship/decisions made with the house in the past, I also can’t rule out that the beam was put in slightly crooked to begin with. And/or, that when the adjoining building was built (at which point most of the foundation on one side was removed and the bolted 2×8 post installed) 50 years ago, the temporary supports they used weren’t enough and the beam shifted slightly back then. That may well be the cause rather than the bowing. The bowing was caused by too much weight on the rafters (third layer of shingles), which then curved inwards in the middle, putting pressure on top of exterior walls to go out. The bow was slightly visible but since we did that rafter fix it’s not detectable anymore and roof structure is more than strong enough.
*Can you provide a description of how one would anchor that size beam to a concrete wall?* Something like a joist hanger, a 90 degree metal plate fastened to beam and foundation on one side? I’d think a giant bolt through the top of beam down into wall would do it, but space way too tight for that. Was thinking we could put a thick steel I-beam where the cut is made (running the length between basement window and carrying beam), and set that into the concrete below with concrete, and the lumber above with some fastener.
We consulted a structural engineer previously on the roof fix so may give him a call again, he’s a little pricey but like you said, ounce of prevention.
restorationcontractor | 4 years and 6 months ago
It’s a fairly thorough written description, however you should post photos to get a better idea of the existing conditions.
Just going by your description it seems like if the existing concrete foundation wall is in good shape there “probably would not be an issue”.
Is the carrying beam end anchored to the foundation? You might want to do that.
From what you described as I understand it the carrying beam is there to support bearing walls on the first floor that are transferring part of the roof load down to the carrying beam and then down to the cellar column footings.
It’s not a simple carrying beam just there to reduce deflection (think bouncy floors) on undersized first floor joists.
(Don’t forget about snow loads as well.)
I would be more concerned about the cause of the beam twist and the exterior wall bowing.
With the other issues you described I would have a structural engineer and a qualified contractor take a look at this. An engineering consulta tion is not that expensive.
You don’t want to do something stupid that could cause damage and that your insurance company won’t pay out on. Or worse yet someone getting hurt because it’s not safe.