Rim Joist

Repair help for the do-it-yourselfer.
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Moderators: Mark, Greg, mhrAJ333, JD

Posts: 6
Joined: Sun Mar 30, 2014 9:23 pm

I'm new to owning a MH, but do have some repair knowledge. Found that the rim joist is rotten from rear master bathroom to front door (approx. 50 ft) and most of the floor joists are rotten where they join the rim joist. Wall joists are OK. My plan is to support the floor from underneath the MH & again on the inside from the floor to ceiling before I start replacing rim joist. Any info on doing this repair will be greatly appreciated.
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Posts: 5696
Joined: Wed Feb 28, 2007 8:01 pm
Location: Weedsport, NY

You can do a search on the topic, Many here have done the repair. It is not that hard, But it is time consuming and can be dirty.

"If I can't fix it, I can screw it up so bad no one else can either."
Posts: 79
Joined: Sat Jan 01, 2011 11:25 pm
Location: Huntsville, Alabama

Edit...Get rid of all rotten wood from under there!

The methods that I've used repeatedly on my rentals:
You'll have to remove underpinning and peel open the sides (only at the bottom 1/3) of your mobile home...do only as much as you can repair and close back up in a day's time
CAUTION: If working on a really windy day, the metal siding can slice you wide open!!!!!!

1. Do each floor joist one at a time, otherwise doing several at once will create sag
2. Do not replace entire floor joist; just sister one new joist-piece on either side
3. Each sister joist-piece should extend at least 4 foot beyond the end of the rotted joist area
4. After you've installed two sister joists per each original joist, remove rotted rim joist and install new rim joist boards, use perfectly straight boards; I prefer 12' boards
5. Remove only enough rotted rim joist to get the first new 12' rim joist installed; there will be lag screws run up through the metal outriggers into the bottom of the original floor joists (remove and replace upon finishing the repair)
6. For each new rim joist, secure one end (2 sister joists) of the rim board with three 3" deck screws into your sister joists and do the other end of the rim board; then do the middle joists
7. Secure the rim joist to all butt ends of all sister joists for the 12' span...you may need to use an automotive jack on ply wood on the ground to raise all remaining sister joists to the proper height before screwing into butt ends of the sister joists
8. MOST IMPORTANT STEP OF ALL...find out how the water got there in the first place and FIX IT!
Two 14x66's