I looked at a deck yesterday that the HO wants to add a sun room to. The deck is 12 years old and in excellent condition. Joist are 2×8 at 16″ o.c.. Ledger board is through bolted to the rim joist of the house and properly flashed. Outside post are 6×6 at 8′ o.c.. Joist at the ledger are in joist hangers, but the ends at the post line are not. The “beam” at the post is a single 2×8 also through bolted through the 6×6 post.
The enclosure to be added is an insulated aluminum panel system with windows that will bare on the outside edge and the 2×8 gutter board nailed to the trusses for the roof panels. Haven’t got the numbers for load that the total system will add yet. (someone else is doing the enclosure)
I do not feel the outside beam is large enough. It should be at a minimum two 2x8s, and the joist should have hangers installed on them.
My proposal is to add another 2×8 to the “beam” and the joist hangers.
All of the nails and through bolts are galvanized, but I do not know if they will survive being sandwiched under the new ACQ 2×8 I add.
What say yee wise and worldy people of great wisdom?
Will the new stuff eat the old galv. fasteners?
Would a better solution be to add new 4×6 beams in hangers between the post? This will lower the head room under the beam, but the deck is 8+ feet high with a patio underneath, so it should not be a problem.
Which option is best?
Dave
Replies
How about bolting a new beam to the posts, under the existing joists. That way, the only hardware to corrode would be the bolts through the beam and posts, and you could use big ones (5/8", maybe) and pre-treat them so corrosion wouldn't be a big concern.
Al Mollitor, Sharon MA
How big is this deck? Double 2x8 on ouside is probably good idea and adding joist hangers also good. Someone posted here that the new ACQ won't corrode fasteners if kept dry--if the hangers are under the now enclosed deck, maybe they'd be dry enough. When the gurus of engineering see this, they will undoubtedly respond with better advice. Knowing size of deck would help though.
12x32'
I am also installing 1/2" plywood inside the enclosur for carpet. The whole deck will be covered, but only half of it enclosed.
My concern is that the single 2x8 on the outboard side won't be enough for the addtional dead load and live load. I have visions of the current patio furniture being replaced with couches, chairs, tables, etc., at least in the new room. The patio furniture and gas grill will move to unenclosed, but now covered half of the deck. The joist are adequate for that span and live load,but not the outside single 2x8.
Dave
Yeah, single 2x8 does seem inadequate. I have a book with tables that tell you the sizes of lumber needed for various applications, but is probably something available on net or at library. Building dept. may have certain requirements too.