deck expansion/contraction

do P/T decks expand and contract? floating deck has wall abutments on four sides. Do I need to leave outside dimension space for expansion?

 

The pt will expand and contract laterally with the seasons. That is why you leave space between deckboards when installed in the winter (here in the south). You shouldn't have alot of expansion in the framing lumber in the longitudinal dimension. But since you have a 4 wall abutment, you will be bolting the rim joists to the structure, you can also leave a small space at each intersection if you feel it will expand too much.

 

I want to avoid tying into structures if possible (free floating idea) i layed rubber base over epdm to protect it from 2 x6's but up against this one wall can be cut back if need because one wall has a gutter so 4 inches off wall is useless. my 5 foot latice (privacy wall) will not be able to butt up against this one wall. so if the framing lumber will not expand much i can leave it or to be on safe side cut it back? It is not a big deal to cut 2x6 but if i don't have to better for me. i'm in Rhode Island. This is a roof deck over epdm roof over looking a plaza.

 

OK, additional info is good. Free standing on EPDM on edge is not a good idea. You should use flat pieces of 2x8 along the length of the joists to broaden the pressure on the EPDM. Don't make them solid, as the water has to drain. Your problem of expansion or contraction will be the least of your worries if the EPDM ruptures. Just wanted to interject that so you could prepare yourself in your insallation. If the tolerances you are worried about are less than 1/4", you are OK.

 

thank you my rubber walk pads from roofing supply have round dimples have i 24x24 i cut them to six inch wide layed them end to end 2 inches apart for expansion(roofing guy tip) 2x6 p/t planks on that(lenghtwise). 2x4 studs perp to 2x6 16 oc next. sort of like a lay down wall partition. Decking then will be laid perp to 2x4 taking in to account expansion. nail space between those should be adequate?. 4x4 posts on corners on 2x6 with 2x4 cross beams for for stability. in addition want to put lats diag to post on cormers for more stability i will have to toe screw since i will be locked out of face tacking. (unless i build deck up on end and lay down over planks but my help is no where to be found. between dimples and spacing between pad seems like i will get good drainage to roof drain that will be below deck(will have to box in skuttle hole for access to that. does it sound like my direction is good? I was skeptical without feedback as this is my first try at decking. laid base tonight hopefully finish tommorrow thanks.

 

It sounds as if you have it all covered. I have just seen flat roof decks without the support to spread the weight, sink into the roofing and cause terrible damage below. That is why I expressed concern. Since you won't have outside nailing capability, you may want to consider inside corner brackets with screws. Just a thought. Help always senses hard work, and vanishes, but don't worry, they will return when the first party is thrown.

 

inside corner brackets you say? On my way to lowes now i get those also. thanks

 

Hey Chandler, Should I space my feestanding deck boards? What if you are building a deck in August in Humid southeastern NC? We also have lots of afternoon thunderstorms.
Thanks