Hi All,
Just wanted to get an idea as to the rhyme or reason for doubling a rim joist. I’m planning on building a deck and in my reading and observing I see some decks with a single rim joist and others doublod. I’d love to know what the rationale is…
Thanks,
Dave
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Replies
i actually joist, block, joist on outside rim joists because i like the plate to have bearing on width full . exterior walls in certain parts of the country are 2x6 and to have that 5 1/2 " sit on 4 1/2" is more preferable the plate wont roll under the weight. it does cause a problem for the plumbers/electrician some times but structual integrity comes first. just adouble rim for a 2x4 wall for the same reasons,it's a better job. for a deck it gives the rail more to attach too. i notch my post maybe 3/4" so it leaves more the post to attach to the double solid rim . or again joist -block- joist ,and knotch the post to slide in between the two solid joists, hence the block . so there would be ####1 1/2 bayonet like piece protruding from the bottom of the solid post. and lag that pilot the holes and off set them. but for big sprawling decks , i just notch the post 3/4" and the rail is set 3-4" from the edge of the finished deck.... there are a dozen diffrent scenarios.. have fun.. slainte' b
You say deck so I presume you mean porch type deck. sometimes the floor of a house gets called the deck too. Framing a floor , you are over a foundation so the rim is mostly a nailer is all.
But a deck is usually spaned from post to post. Sometimes that happens with abeam under the joists, but other times, the rim joist also functions as the beam, flush settting, so it ne4eds o be doubled or triopled - whatever it takes to span and carry the load.
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Aha...thank you both, now it makes sense to me.
Read up on exterior deck construction before tackling one, if you're building this for yourself and aren't a pro.
There are a lot of things to know about rot prevention. Someone here should chime in and tell us which magazine recently had an excellent reference article on this topic.
For example. Don't double up or triple up 2x members to make beams with more carrying ability. Use 4x or 6x solid sawn members instead. Sandwiched pieces invite moisture retention in the interfaces, and rot quickly.
Learn all you can about ledgers, best practices, etc.
Thanks Gene, will do. Read, read, read, learn, learn, learn, breaktime, breaktime, breaktime!
The last issue of JLC had an article on decks and talked about the sandwich issue. Good reading for anyone about to build a deck. I think if you go to their site you can pay a couple of bucks and read the article online.
that 's a good point ... i built a deck , my own and these are eighteen years old and no rot. what it does need is a real good power wash with an anti-fungicide , but that's another instance. i would probably have them , put some grace ice/watershield over the top of the "sandwiched" components. although weather worn and needs a wash i think the reason mine has lasted so long is its 10 feet in the air and i got good drainage, air circulation, and the sun hits it and it dry' s well ........but still your point is more valid..... regards ...bear"expectations are premeditated resentments"
Espo,
Another reason to Dbl the rim is to leave the outside permitter flush with the top of the deck boards. Kind of a frame so you see no end grain in the deck boards. It will also allow the rim to be used as a carrier for the joist in leu of another beam near the front or ends of the deck.
Garett
Sometimes, to provide a neat appearance, two rim joists are used, one maybe an 8x and the other a 10x. The 8x is placed under the deck boards, the boards are cut off flush, and then the 10x is added so that it's top edge is flush with the deck surface. This provides a neat edge with no exposed cut ends.
Technically in this case the outer board is a "skirt" or some such and not a joist, but most of us tire from trying to remember all those specific terms (and their regional variations).