New patio with pressure treated wood

Old 10-13-09, 08:43 AM
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Join Date: Oct 2009
Location: ARKANSAS
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New patio with pressure treated wood

HELLO,I'm new to forum but any info would be appreciated!
We live in new home with ugly concrete slab out back door
(L-10' / W-14')Like to put wood patio on/over it about
(L-14' / W-18')My back door step is 5 1/2" to the slab can i use 2/4 or 4/4 along the back of house and support it by
4/6 on each end in concrete holes and lag? it in slab?

4" WOOD PLUS PLANKs are APPX 4/5= 1.25" THATS 5.25" THAT
LEAVES 1/4 IN FROM TOP OF DECK TO TOP OF STEP,should i raise 2/4 or 4/4 off the slab 1/4" to have it even with step?
can i do any of this or any ideas and help would be appreciated
p.s have more questions if this can be done
thank you
Old 10-13-09, 11:19 AM
Join Date: Mar 2000
Location: Arlington, WA
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Welcome to the forums.

The problem with laying wood, even treated, directly on concrete is that it'll trap water and debris, which will cause it to rot. You could get around that by wrapping each of the 2X4's or 4X4's (whichever you use) with Vycor -- first across the bottom and fold it up each side, then across the top and fold it down each side.

You have 5-1/2" of height to play with. A 2X4 on edge or a 4X4 is 3-1/2" thick. Add another 1" for deck boards (assuming that you use 5/4 decking) and that leaves the deck an inch below the threshold of the door.

The slab (assuming that it was poured properly) slopes away from the house -- probably 1/8" or 1/10" per ft. That's fine, but you'll have to have the sleepers (the 2X4's or 4X4's) run perpendicular to the wall of the house and the decking will be parallel. Are you sure that you want to make the deck 18' wide? Deck boards come in lengths of 4' increments -- 12', 16' and 20'. Also, since the slab is on the ground, how are you going to support the sleepers once they get past the edge of the slab? If it were me and I was going to do it that way, I would add a 1' strip of concrete to each side of the existing slab (or 2' on one side) and make the deck 16' wide. (No waste in the decking.) If you want to go 18' wide, increase the width of the concrete strips, use 12' deck boards and stagger the joints in the decking.

The 14' projection for the deck when your slab only has a 10' projection -- more concrete to support the sleepers.

If you use 2X4's for the sleepers, attach them to the slab with Simpson L30's or L50's that are Tapconed to the slab. If you use 4X4's, redhead them to the slab -- countersink the redheads.

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