Bearing wall replacement

[Countryboy1604]

Hello
I am new to this forum so please excuse me if I am awkward in explaining what I am doing. This is a repair project at my cottage property. The crawlspace is always wet and the untreated bearing wall is always damp. I am concerned that it will eventually weaken and fail.

I need to replace the 2x4 stud wall(16"oc) that currently supports 12' spans of floor joists on both sides. The cottage is 24 x 36 and this wall runs down the centre of the crawl space for the entire 36' length. The structure is a1.5 storey conventionally framed house. I have already researched the girder and columns I need (thanks to some great info on this forum!) and have a firm plan for that part.

My question now is about footings. The current wall has a poured concrete footing underneath (don't know the depth) that is about 6" wide. Since the original construction was done in 2005 I am assuming its fine for supporting a wall with studs at 16" spacing. I am replacing this wall with a girder and posts at 6' intervals. I suspect that the existing footings will not be sufficient because I am now concentrating the load on a smaller number of post locations.

Could the existing footings be OK with the load spread at 6' intervals? Any ideas on how to either enhance the existing footing or how to determine the size for new ones?

[Don_P]

I think the first order of business would be to dry the crawlspace, if it is constantly damp under there you'll have mold problems. Gutters and downspouts directing roof water away and a perimeter drain outside the foundation should take care of that most of the time. There are a couple of schools of thought on proper ventilation methods, basically either naturally vented or sealed and conditioned. It should be dry and then a 6 mil or thicker vapor barrier applied over the soil.

The simplest way of using the existing foundation would be to replace the untreated framing with treated wood by lightly jacking and shoring a section of the floor at a time, replacing that section of the wall, then moving down and repeating. This should have been caught and corrected at the framing inspection, treated lumber as it's closer than 12" to ground.

At 6" wide on damp soil I imagine you are right that the existing footing is inadequate for spot piers. You could either remove sections of the existing footing to gain access to an area large enough for replacements, go down to undisturbed soil for the new or excavate around the existing wide enough, long ennough and deep enough to put in a new footing under the existing one. Do not call the existing footing part of the new one, the existing footing would be supported on top of an adequately sized new one.

[Countryboy1604]

Thanks!
I had not thought of replacing the wall in sections with a new PT framing.  I jumped to the girder and posts idea because I thought I could avoid jacking and potentially disturbing the tile floors above. The missus will have my head if I crack her new tile floors!

The idea was to build a girder on both sides of the wall and sandwich the wall between.  I would over-build the girders for safety... the table says 3 ply 2x8 for a single beam and I would use 2 ply 2x10 on each side. I would then support both with a 12" cross member (3 ply 2x6)beneath and wedge the posts in tight under that. The existing wall could then be cut away afterward. Do you see any flaws in this approach?

The thought of simply framing up replacement sections of wall sounds a lot easier and I may reconsider jacking the floors but I wanted validation that my first idea would work or not.

The wet floors probably can't be fixed. The area is a little swampy and I mis-calculated how high the spring runoff would push the level of the ground water when we sited the foundation. The natural drainage path is blocked by a roadway and the local municipality is unlikely to put in a new culvert, especially because there is another property between. Once I get the wall fixed I plan to thoroughly insulate and seal off the floor above to keep the moisture contained. Unless anyone has a better idea!

[rick91351]

I would first put in a french drain.  I would make sure that there is no leaks under that house like a drain from the bathroom lav that never got sealed up.  You would be surprised!     Get the down spouts way away from the house.  This problem will shorten the life span of your house and maybe health issues.   

You do need to get that dried up.  It is a health problem waiting to happen.....  Mold and mildew are health issues waiting to attack. 

Get it dried out then fix the other issues.........

Just my humble opinion   

 

[Don_P]

I agree, you need to dry it out. Perimeter drains leading to a sump pit with an ejector pump is the way to get rid of water if you are below the water table. We did one pair of houses, a family compound, that the homeowner decided to put the basements 2' below the pond out back. The static level in the basements was 2' whenever we stopped pumping. I'm not recommending ever building that way but we put a large sump in each basement with an electric and a battery pump in each and it worked.

Moving anything structural under tile is asking for trouble, even drying saturated swollen framing under there may crack it. The tile floors should not have gone in ahead of fixing the moisture problem, now its' just a gamble you'll have to be prepared for. A girder assembly is more flexible than a wall assembly and installing new treated girders or framing is going to carry some shrinkage and settling with it, either of these can crack the tile.