stabilizing a very old house. HELP

[Daddy-0-]

I set out to repair some rotten siding and as I started opening up the outside, I discovered some major but old powder post beetle damage. The house is circa 1754 and is post and beam construction. The studs and joists and diagonal bracing seem ok, but the sill beam is completely shot. The sill was 14 X 12 heart pine and has about 2" of good wood left. Will be getting a permit tomorrow. Ugh. I have built a temporary wall in the basement to support the floor joists but I need to support the exterior load bearing wall so that I can remove the sill beam and replace.

I was thinking about bolting an LVL to the studs on the outside and posting down with a temporary wall set on a wide plate on the ground. Thoughts?

Any suggestions welcome. That wall has sagged about an inch over the years. I cant believe it hasn't failed.

 

[GBrackins]

I've had to do this on a couple of projects over the years. Seems the north side sill beams around here are the worst. Your approach sounds dead on. We have lots of rubble stone foundations so I routinely install a pressure preservative support wall (abutting the interior side of the foundation wall)to carry the floor load, install a ledger plate (at the second floor level, a lot of balloon framing) to the outside of the dwelling secured to the studs and use 2x8 diagonal bracing notched (about 30 degree angle to wall) to support the ledger plate down to a 2x12 plate on the ground secured with 2x4's driven into the ground on either side of the 2x12 about every 48". The sill beam is then cut our in small sections and replaced. Typically leave the wall inside the foundation.

You seem to have the right approach, at least per my experience. Good luck!

 

[dhengr]

Daddy-O:

What is the foundation below the 14x12" sill beam, and what is its condition? Draw a full height wall section sketch, showing framing above, dimensions, etc. I assume some of these ext. walls have floor framing above running parallel to the ext. wall, thus fairly lightly loaded; others have floor framing and roof framing onto the wall, thus more heavily loaded. What are the loads on the walls, on the posts? If it’s real post and beam, then most of the loads are concentrated at the posts, and the studs are sorta just infill for the int. plaster and ext. siding; but the studs will be loaded too. Do the posts rest right on this large sill beam, or is there a smaller sill under them, atop the larger sill beam? Maybe do one post at a time, and the posts may have tendons into the sill beam. Lag a shear bracket onto the post and lag a 6' long beam up under this and to the post. Jack on both ends of the beam until you just unload the post, slowly, plus whatever settlement has occurred. Cut about 2' of the large sill beam out and build up a conc. blk., core filled, pier for the post to sit on. After you’ve done the posts, remove the rest of the large sill beam and lay blk. under a new sill pl. That might be one solution.

I’d really have to see the exact sizes, dimensions, framing situation, and details to comment in much more detail. In any case something like this needs some thought and engineering before you get started.

 

[Daddy-0-]

The foundation is 18-20" thick solid brick in multiple layers and is in pretty good shape. The framing is all post and beam with mortise and tenon joinery.

 

[Daddy-0-]

Will try to upload a pic tomorrow

 

[DRP]

Timberframe, wood joinery and connections, post and beam, steel plates and connections.

Also while you're in there, whenever I can get to the timbers I borate them heavily. A cheap mix that is chemically the same as Bora-care is to go to a real farm supply and get a 50# bag of Solubor or 25# of Beau Ron, mixed at 1 lb/gal of warm water makes a 10% solution. Antifreeze, ethylene glycol, mixed in at ~ 1/4 to 1/2 gal /5 gal of solution to aid in wetting and slow the drying. Actually any glycol will work, RV antifreeze (propylene glycol), Go Lytely (polyethylene glycol), etc, they just dry slow and let the borate penetrate deeper. 1.5 lbs borate/gal is a 15% saturated solution, use all of it that day if you mix that concentration, it'll crystallize rapidly as it cools. Rinse the sprayer well when you're done to prevent crystals from clogging it up. Multiple wet on wet coats for as long as you can. The borate ruins the gut in any wood consuming insect and inhibits the growth of decay fungi. I noticed the powderpost hatch beginning here the other day. In heart pine I doubt it is a true PPB but the borate will kill any insect that ingests the treated wood.

If you look at old european frames there are sometimes notches mortised into the lower ends of columns from lifting and refitting the sills.