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Sill plate/ Joist evaluation and replacement

516 Views 1 Reply 2 Participants Last post by  Nealtw
I'm living in a home that I'm a renovating and have a few questions about sill plate replacement. The house is 1930's balloon framed and has shiplap sheathing covered in multiple layers of siding. There was a carpenter ant infestation when I first moved in and discovered it when they swarmed one spring. The ants did some substantial damage from the sill plate to the top plate on the second floor.

There are several places where I'm not sure if the damage is significant enough to warrant replacing the material or not. For example, where the ants made their entry into a sill plate the damage only appears to affect a small area of the plate (less the a foot wide). Other places joists were damaged seemingly superficially, where the ants were between drywall and wood, not more than an inch into the height of the joist.

Another issue I've noticed with a sill plate is on an addition from the 1960's. The plate has obviously been water damaged repeatedly. There is no tar paper or gasket between the wood and block foundation. The foundation there leaks like a sieve. It appears to have a white haze and the wood feels relatively soft when I use my finger nail to gauge it.

So my question is, how do you determine whether or not to replace them. If you do replace a plate, does it need to be anchored into the foundation? If it does need to be anchored, I imagine you'd have to pull the floor above and sink expansion bolts through the new wood. Does anyone know what code generally dictates for the anchors?

On studs and joists, does it matter if you pull the damaged wood out rather than just sister or scab along side it? Are there pheromones left behind that would attract the ants? I've read that they need a moist environment so hopefully if I have a weather tight exterior it will be ok. I thought I should coat it all in Boracide or dust it with boric acid after I reframe it. Any thoughts are appreciated. Thanks.


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You can judge the wood condition with a sharp screw driver, ice pick, or awl. By comparing it to good wood of the same grade and age like the other end of the same joist.

There are other ways to anchor a sill plate. Rot is always the next thing to attack wood especially if it has been getting wet. It is never a bad idea to paint any questionable wood that will be left in place with end cut treatment for treated wood

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