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How do I repair or replace a water damaged band joist

0 votes
I recently pulled out some batted fiberglass insulation that had been up above my basement concrete wall in the band joist area. I have been able to determine where a water leak had originated from and seaped down into the band joist (also sometimes called header joist or just plain band board). I am obviously going to need to repair  the area outside of the residence where the water leak originated. However, I have some significant water damage (rot) to an area of the band joist that I do not know how to repair. The band board is made out of the commonly used pressed wood or sometimes called chip board. Do you have any suggestions on how to repair or possibly even replace a section of water soaked board in between the joists ?  rot covers a length of three joist sections. FORTUNATLY, no damage is evident to the joists themselves.

I know that I need to repair the area outside of the house first where the water is coming in, before work is done on the band board.

Thanks in advance for any help you can provide.
asked in House Foundation by jess (150 points)
    

1 Answer

+1 vote

 

Hi Jess,
 
There are a few possibilities; one would depend on what kind of a wall finish you have on exterior and how easy (if possible at all) it could be removed to access this deteriorated bend joist. This way you could replace the entire damaged section at once. This could be the easiest with vertical types of siding boards and other wall finishes that can be disassembled without damaging them.
 
If exterior access is out of the question, you’re left with cutting out rotted sections from between the joists and replacing it with new boards (I’d recommend pressure treated wood). You can remove existing board by chiseling it along the floor joists in each joist space, using a Sawzal, Rotozip, or any other tool you may have available. 
 
In case there’s a double board or some extra space behind the band joist (between the joist and the exterior wall finish), you might be able to cut one longer (full required width that fits behind 2-3 joists) replacement board from a thinner, treated plywood, and try to slide that longer piece behind the floor joists (one piece at a time / 2 or 3 layers of that thinner plywood to match original thickness).
 
Depending on the design of your floor frame this may or may not work. If one, full width piece will not fit, use smaller sections to fit between the joists.
 
Another option is to remove any loose or heavily deteriorated sections of boards, allow the remaining wood to dry completely, and install new boards over the old ones just to cover the holes. 
 
All of the above can be applied only if this bend board isn’t supporting your floor joists; the floor joists are fully supported by the foundation or other structural formation. If it acts as a ledger board / floor joists have been improperly installed (too short – look at a drawing below) you need to first support them properly so they will not depend on the band board’s integrity.
 
Insufficient floor beam support
 
Let me know if you have additional questions, just click “comment” below
answered by admin (21,370 points)
First of all, I want to say thank you very much for your timely response to my question. Your very first option which was accessing the rotted band joist from the exterior to remove the rotted wood is out because the damage occured behind a brick soldier course in the front door entry system. The second only option would be to cut out the rotted wood from the interior. There is no double board behind the band joist, but there appears to be some extra space between the rotted band joist and the brick soldier course outside. I just don't know though how I would manuever a FULL width replacement board, from a thinner, treated cut of several pieces, just behind the sill plate and into position behind 2 to 3 joists. Based on the design, I'm left with using smaller sections to fit between the joists.  The last option suggested is to remove any loose or heavily deteriorated sections of boards, allow the remaining wood to dry completely, and install new boards over the old ones just to cover the holes. I only had a neighbor's friend take an observation of the problem and that was a suggestion. I thought this option he gave was a little far stretched at first. Now that you've concurred, do you believe installing new pressed board (i.e. chip board) to replace the rotted wood that I would remove be my best solution? Also, how would I know if the band boards are actually supporting the joists? I actually thought the band joist board only served to prevent the joists from swaying in the area before they nailed down the subfloor, which when after the subfloor was added, the band board no longer provided the integrity to support the joists even though they're still nailed to the end of the joists. Is that in fact true?

 

Hello Jess,

Just like on this drawing above, in some cases the band joists are the same thing as the beam. This drawing shows one flat piece of wood (foundation sill plate) / usually a 2x4 or 2x6 inadequately supporting the beam.

If your floor joists sit on a sill plate (picture below) than you can safely remove the band board or parts of it. If the floor joists are “hanging” past the edge of the sill plate (again, drawing above) or the foundation itself than you should provide support for them.

Floor joist supported on the foundation wood sill plate

Covering only partially removed rotten section is not the preferable method but if those band boards have no structural significance and complete replacement might be difficult (or impossible), it’s just your conscience, awareness of some cosmetic issue hidden behind a new piece of wood.

Just make sure the source of moisture / leak has been eliminated and the area completely dry before covering it.

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