# Installing deck ledger board over foam board?



## RickT (Oct 2, 2006)

My house is being resided and I'm planning on building a deck next spring. I thought that as long as the old siding is coming off, now might be a good time to install a ledger board. My house sheathing is 1" foam board, not OSB. Should I install the ledger board over the foam board, or should I cut the foam board away to expose my sill plate, install pressure treated 2x? ledger board to the sill plate? I was thinking that the foam board would compress and would never allow a solid enough installation of the ledger board, but I wanted to ask you guys. 
Thanks,
Rick


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## Big Dave (May 17, 2006)

I would advise to cut the foam out and replace with osb. I've worked for people who nailed over the foam but like you said it just isn't as strong of a bond.


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## AtlanticWBConst. (May 12, 2006)

RickT said:


> My house is being resided and I'm planning on building a deck next spring. I thought that as long as the old siding is coming off, now might be a good time to install a ledger board. My house sheathing is 1" foam board, not OSB. Should I install the ledger board over the foam board, or should I cut the foam board away to expose my sill plate, install pressure treated 2x? ledger board to the sill plate? I was thinking that the foam board would compress and would never allow a solid enough installation of the ledger board, but I wanted to ask you guys.
> Thanks,
> Rick


RickT...your intuition is absolutely, 100 % right..... about the foam...:thumbsup: 

Install your ledger board onto your sill plate....

However, what we do is to make sure that the areas is water and moisture tight:

a.) The area of the sill plate and wall sheathing is covered with a water and ice shield membrane.
b.) Install spacers between the ledger and the sill plate to allow water and moisture run-off.
c.) Install proper aluminim (or other proper material) ... capped & bent ....over the ledger board....away from your house...


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## North Country (Nov 5, 2006)

Cut the foam away, then slide flashing up underneath the foam/bend so it comes out over the top of the ledger board, then install ledger to floor rim joist.


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## RickT (Oct 2, 2006)

Thanks, guys. The foam board goes. Of course I'll be sure to properly flash the ledger board. Now I have another question. The aluminum sill of the patio door I just installed cantilevers aboaut 1 1/4" passed the foam board. Cutting the 1" foam will leave 2 1/4" of the aluminum sill cantilevered passed the rim joist. Installing 2x? pressured treated ledger will leave the aluminum sill cantilevered 3/4" passed the ledger board. Is that OK? I guess I'd like the first decking board to be flush with the aluminum sill rather than tucked under it or above it. I also don't want to leave 3/4" of the aluminum sill unsupported because I expect it will bend over time as it's stepped on. Should I install two pressure treated 2x to make essentially a 3" thick ledger board that fully supports the aluminum sill and stands proud of it by 3/4" instead of coming short of the edge by 3/4"? Also, I have a sample of the decking I plan to use, so I can determine what height to install the ledger so that the decking comes flush with the aluminum sill. 
Thanks again,
Rick


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## Darylh (Jan 2, 2006)

Deck surface is usally 2 inches below the finished floor of your house or at the very least your deck boards should tuck underneath you door cill.I know you don't like this but if the wind blows in a rain storm you could get leakage into the house.


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## tharnden7 (Apr 27, 2018)

RickT said:


> Thanks, guys. The foam board goes. Of course I'll be sure to properly flash the ledger board. Now I have another question. The aluminum sill of the patio door I just installed cantilevers aboaut 1 1/4" passed the foam board. Cutting the 1" foam will leave 2 1/4" of the aluminum sill cantilevered passed the rim joist. Installing 2x? pressured treated ledger will leave the aluminum sill cantilevered 3/4" passed the ledger board. Is that OK? I guess I'd like the first decking board to be flush with the aluminum sill rather than tucked under it or above it. I also don't want to leave 3/4" of the aluminum sill unsupported because I expect it will bend over time as it's stepped on. Should I install two pressure treated 2x to make essentially a 3" thick ledger board that fully supports the aluminum sill and stands proud of it by 3/4" instead of coming short of the edge by 3/4"? Also, I have a sample of the decking I plan to use, so I can determine what height to install the ledger so that the decking comes flush with the aluminum sill.
> Thanks again,
> Rick


Rick, I have the exact same situation. What did you end up doing and how did it work out for you?


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## Nealtw (Jun 22, 2017)

tharnden7 said:


> Rick, I have the exact same situation. What did you end up doing and how did it work out for you?


This thread is more than 10 years old. today you build your deck 6" below the floor the flashing can not be aluminum. Something like peel and stick between ledger and the house is a good idea The siding should start about 1 inch above the finished deck height. Ledger would be lag bolted to the house and that can be done after joists and hung so you don't have a problem with planning their location. If you want to maintain as much foam as you can put one flashing behind the foam and another in front of the foam both right on top of the ledger tape the second one to the foam and start the siding 1" above finished deck.


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## tharnden7 (Apr 27, 2018)

But that doesnt address the fact that there is 1" thick foam between the sheathing and the siding. Plus the thickness of the siding leaves a 3/4" overhang above the ledger. Should I use spacers to bring the ledger flush with the siding or keep it recessed?


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## Nealtw (Jun 22, 2017)

tharnden7 said:


> But that doesnt address the fact that there is 1" thick foam between the sheathing and the siding. Plus the thickness of the siding leaves a 3/4" overhang above the ledger. Should I use spacers to bring the ledger flush with the siding or keep it recessed?


I would leave it recessed, all that just helps keep it dry.
If you are placing decking on an angle you would have to add blocking at that end


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