How To Repair Your Homes Rim Joist And Sill Plate

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    A friend asks about some water damage he found along his foundation when he removed his deck and he is wondering just how hard it will be for him to do the work himself or if he needs to hire a structural engineer and a contractor.

    The problem is pretty common on homes that have attached decks where the contractor didn’t take care to make sure the home was waterproofed before he attached the deck to the home.

    As you can see there is some pretty serious damage that must have happened over many years. The rim joist which is the 2″x12″ board that runs around his foundation and maybe some other items need to be replaced.

    This should not be looked at as something easy to do yourself if you don’t know how to frame a home but it is well within the ability of anyone that is handy and healthy enough to do the work.

    The first thing you want to do is build a stud wall inside the basement of the home to support all of the floor joists in that area. This might mean taking down a drop ceiling or drywall but you want to get back to the joists and framing lumber and then install a supporting stud wall made of 2×4 studs to support that area. Make sure the stud wall comes in contact with the floor joists and there should be some compression so when you build the wall you want to install the top and bottom plates and then hammer a slightly longer board into place. It is expected that you know the basics of building a stud wall if not you will have to check our other HowTos. You want the compression to take the load off the wall.

    In all probability the inside plate of the wall which is where the floor joists rest is probably not fully rotted out or the home owner would have felt a springy or spongy floor in that area long ago but it is not something that you want to depend on while you perform the work.


    Now that the wall is stabilized you can begin inspecting how much rott there is and what you will need to replace. Hopefully it is only the rim joist and the sill plate and the rot does not extend into the joists, the subfloor or other areas.


    The next thing you will need to do is remove all of the rotted wood and then cut new sections of wood to replace the old. Since the new wood is probably not going to fit in the area if it is sagging you may need to use screw jacks in the basement and then shim your temporary stud wall to support the joists again.

    The sill plate should be made out of pressure treated wood but all other lumber that you need to replace should be standard framing lumber.

    Make sure that you attach the joists securely to the new rim joist with common 16p nails. There is no need to use galvanized nails in this area.

    When installing the sill plate you may find that it was held in place by anchor straps or bolts. Don’t cut these things when you are taking the rotted lumber out you should be able to reuse them on the new sill plate.


    Final Note

    This is a pretty quick explanation of a task that might take you a few days to complete. It will all depend on how much other damage there is and you won’t know that until you look closer and remove the damaged boards.

    If your floor joists are rotted you will need to sister new ones on to the old ones and I like to nail the boards from both sides on a angle and then also use construction adhesive to reduce squeaking.

    This is a project that one person can handle but obviously it will be much easier with 2 or more people.

    Remember be safe and install that temporary stud wall before you start poking around.

    If you are replacing the deck you will need to waterproof that area with a rubberized membrane and flashing so this problem won’t happen again.

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