Steel shim vs. non shrink grount for a sagged wood beam
https://imgur.com/a/mfTPJyc
Hi All,
This is my first post here. I am going to go through an extensive renovation for my house next year. It is an old house built in 1933. The main floor and second floor are sagging around 1″ in the same position that is close to the beam end in the photos. The beam rests on two concrete foundations and a wood post in the middle.
I will ask an opinion from an engineer when I open all the walls and stuff. In the meantime, my plan is as follows:
1. Jack the beam with bottle jacks.
2. Add some steel shims instead of rocks.
It seems we can also use non-shrink grout but I don’t think I will not have enough space to push the grout under the beam. That sounds simple, right? Please let me know what you think about my plan.
Notes: my old house seems to be pretty level except for one or 2 areas with minor sagging only.
Thanks.
Replies
Be careful here!
Are the first & second floor walls plastered? Do you plan to replace the plaster with drywall? If not, raising the beam 1" is likely to result in cracked plaster in places you might not expect.
Reconsider your terminology. "Sag" is commonly the deflection of a horizontal member near the middle of its span. "Settlement" is what happens at the member's support. Also, with a wood beam of the size shown in your pics, wood shrinkage may have contributed to most of the "dip" in the first floor above.
With homes of this vintage (and older) that have aged well, some anomalies are best left as-is and either considered to contribute to the home's 'character' or concealed with new finishes. Trying to bring a vintage home's structural elements into flat, level and plumb can't be rushed (think in terms of many months or a couple of years) and can often create more issues than the attempted correction(s) will solve. Remember it took many decades to settle into what you see today - it's just not wise to think you can correct it all in a few weeks of home improvements.
My advice - proceed cautiously.
As far as shims go, I'd opt for steel (preferably painted) or HDPE shims. The wood will 'suck' moisture out of any grout used (unless you dry-pack) resulting in cracks in the hardened grout. Make sure you don't seal the end of the wood beam into the concrete supporting wall - the wood needs to 'breath'.
Contemplate carefully but be sure to take time to enjoy the coming Holidays!
[CT structural engineer here]
Thank you for all your notes and they are what I am looking for. I am going to replace all the plaster with drywall for the renovation so cracked plasters or tiles won't be a problem. Some contractors also suggest just to level the floor instead of fixing the settlement. I will wait until I open all the walls and see what the structural engineer says. He may suggest leaving it as is :(
If it were me:
- Jack the beam up
- Clean out any loose material
- Pack in concrete, but not all the way to the beam - leave about 1/8" to 1/4" space. Let it set up. You can use high strength repair mortar and a grout bag to get it in place.
- Shim the beam with asphalt shingles. It won't compress over time, and will make a moisture break between the masonry and wood.
The asphalt shingle suggestion is interesting. All the joists, beams, and posts in my house are resting on concrete directly. Do you think a vapour barrier wrap is enough instead of an asphalt shingle?
I think anything that blocks moisture is fine: vapor barrier, metal flashing, asphalt shingle, etc. I used to work as a mason, and a rule of thumb was to never allow wood to contact masonry in an environment where water could exist. We always used shingle, as we could build it up to a thickness (say 1/4" or less) and not worry about it compressing over time.
If you don't see any moisture damage in the wood beams, considering the age of the house, I'd not worry very much about it. Personally, I always put a moisture barrier in place.