First post. Trying to repair a deck.
My deck joists go into my house (no ledger board). They are starting to rot at the tops of the boards but are still very strong. I want to sister each joist and add new decking on top.
My question is in regards to sistering. Do I simply nail a new deck joist to the old joist? Does the sister joist need to attach to a ledger board or something to provide support?
It seems odd you can just attach a new joist to an old one. Seems like you are just adding weight onto the existing connection inside of the house.
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Bump
I think the lack of response might be that in my experience with these cantilevered “decks” were that often the damage went in beyond the outside of house. Now, the added exterior repair method relies on how good is it that goes back inside.....
If the deterioration continues over time I don’t think many would bet their reputation on it.
But, you’re there and we’re not.
Best of luck.
Thanks Calvin. And I totally understand that.
My question is only really what is the definition of sistering. Is it simply attaching a new board to an old board. Or does that new board need to be supported somewhere other than just the old board?
Your case is a little different than a normal sistering (attaching) a new joist to an existing joist that was, for example, not sized properly and is sagging/bowing or is bouncy.
In your case, the original joist has deteriorated at a point where it exits the house from exposure to the weather. If there is not enough GOOD SOLID material to attach your new joist too, your right. You would just be adding weight.
If you have say 12" of good solid material, you could just cut off the old joist as far as that goes. Sistering joist that is exposed to the weather is asking for more deterioration from moisture building up between the joist.
Likewise, you need to seal out any moisture where you attach the new joist to the existing existing stub out.
Please understand, this suggestion is based on my understanding of what you have posted and may not be complete or totally correct. Good luck.
"sistering' has to be full depth from bearing point to bearing point to meet code.
Is it possible to install a deck ledger?
https://www.finehomebuilding.com/project-guides/decks/install-flash-deck-ledger-start-finish
How far into the house do the existing joists go? Just through the siding? 3 Joist bays in? What is the connection method? These will determine if sistering is recommended.
It seems the existing degradation is superficial and you're concerned that it's going to get worse, and it's not significant, yet. Cause of rot not stated.
Are you adding decking or replacing decking?
When you replace the decking, run a strip of Ice & Water Sheild (self-stick) or 30# felt along the top of each joist. Overhang by 1" each side. This will stop the potential for damage caused by water and debris caught between deckboards and may stop further decay. Perhaps retreating the PT joists at the top edge is also needed.
Hope this helps,
F