Looking at enclosing a porch. Floor is concrete slab, the roof is part of the main house roof. Currently the walls are screened, they will be changed to Pella sliders. Central A/C will probably be added. The porch faces east in South Carolina (far from the coast). The porch slab is about 3-4 inches lower than the house floor, and the porch is at least one step higher than the terrain.
The existing floor is stamped and stained concrete (and not a very good stamping job IMO). Client has decided that the windows will make the porch look much nicer than it cureently does, so maybe a floor change is also needed. Most of the house is oak.
First thought that comes to mind is two layers of 3/4 ply, staggered and 90*, and nail the wood in place. Would you use treated ply for the bottom layer? What about a vapor barrier? (I have no idea if there is a moisture problem, but I don’t think so.) Would you fasten the ply to the slab, or just laminate it and let it float? The porch is about 50 ft long and varies from 8 to 14 ft wide.
Whenever you are asked if you can do a job, tell’em “Certainly, I can!” Then get busy and find out how to do it. T. Roosevelt
Edited 9/28/2004 10:42 pm ET by Ed Hilton
Replies
Since your porch floor is approx 3 to 4 inches lower than your main floor, you have plenty of clearance to put down just about anything. Tape a 1 foot square piece of plastic down on your porch slab and wait a few days before removing it. If the taped area appears wet, then you have moisture migrating up through the slab. If not, slab is dry.
You could attach plywood directly to slab...it's been done this way before....but since clearance height is not a problem, I'd opt to lay down treated wood sleepers and then ply over top. You could use treated 2X4s, or use treated 5/4 deck boards, or even use Trex 2x4s as sleepers.
Easy way to fasten sleepers to slab is with PAF (Powder actuated fastener ) gun...or you could drill holes and use tapcons. PAF does nice work and would be 10 times faster. I'd lay sleepers 12 inch OC if wanting to install Pergo style hardwood floor over top...or install 16 inch OC if planning on installing layer of ply overtop and carpeting or tiling. In between sleepers, I'd opt for Dow ridgid insulation (blue-board). Insulation thickness to be same thickness as sleepers, and simply pressure fit insul in-between sleepers.
I would either install red rosin paper overtop sleepers before installing final flooring, or I would install nothing at all before final flooring. IMHO, plastic vapor barriers promote rot...and 15lb felt might be a little stiff, although if rosin paper was not available,and I wanted a "buffer zone" between the flooring, I'd use the felt paper. After applying the paper install your ply subfloor or your finished hardwood floor.
If wanting a ply subfloor, use 3/4 thick, T&g subflooring by Advantech. This stuff is really good. It's basically water/moisture proof, and strong to boot. I'd use exterior grade screws or stainless screws to hold my subfloor in place; although a nail gun is faster...if nailing, use ringshank style nails for holding power.
Once this is in place, you could easily install carpeting, or even floor tile. For tile, you could install a layer of 1/4 inch hardi backer overtop the ply if you wanted. Some will say you should ...others will say the plywood will hold up if the right type of glue (latex modified thinset) is used. That's up to you.
Should you opt to install a double layer of ply instead of the sleeper method, I think I would use a double layer of the advantech rather than use treated plywood. I would embed the first layer in mastic and then shoot the ply to the floor with PAFs. I would install the 2nd layer of ply flooring using construction adhesive and screws. There is no real need to alternate the 2nd layer perpendicular to the first layer, but you still need to stagger the seams by starting with a half size sheet for your 2nd layer. If your slab is dry, the plywood method will work just fine. The sleeper method gives you a little more insulation and cushioning underfoot, by you certainly could "fly with ply!".
LOL.
Davo
I already knew most of what you said, but had not considered Trex sleepers. I like that idea.
My logic for using treatd ply for the first layer is the same as using treated bottom plates in wall construction.
If there is a moisture problem, could that be handled by putting down a layer of 6 mil poly first?
Whenever you are asked if you can do a job, tell'em "Certainly, I can!" Then get busy and find out how to do it. T. Roosevelt
My two cents on the Trex sleepers.
With my limited experience with Trex, I have found that fastening to it is unstable. I would be afraid that the everyday foot traffic might be enough to loosen the fasteners holding the plywood down.
I`d use the PT 2 x 4`s.....insulation panels between and a layer of poly atop before securing the plywood subfloor.J. D. Reynolds
Home Improvements
"DO IT RIGHT, DO IT ONCE"
Jaybird,
I first got the idea of using Trex sleepers after witnessing my friend ( who is a professional carpenter/builder) do just that when installing a trex deck overtop a flat concrete patio roof/garage. In this case, a rubber (epdm) roof was first installed over the concrete roof. Then extra strips of EPDM were glued down and the Trex sleepers placed over top the reinforced strips. The sleepers were floated, not mechanically fastened. The deck boards were screwed down over the sleepers. The perimeter of the deck was locked in place against movement via skirting boards that were mechanically fastened to the existing garage walls and in-turn the perimeter deck boards were screwed down onto these skirt boards. This and gravity has held this deck in place now for 6 years with absolutley no defects arising from said construction method. Deck is approx. 20 ft X 16 ft.
I do remember that every screw hole had to be pre drilled...it was laborous, but has held up fine. My friend first tacked with nails a regular 2X4 along the front and one along the rear of the sleepers so to keep them all in position..then he placed, drilled, and attached the "field" of actual decking boards to said sleepers...later removing the end boards that were tacked and replacing them with decking as well.
One thing good about the trex ( actual 2x4s by Trex, not the 5/4 deck boards, were used as sleepers), it doesn't rot and it doesn't cup or bow, or shrink after it's installed.
Davo
ED,
I agree with Jaybird, if it was me, I too would probably use the treated sleepers, insulate in-between with the ridgid, and ply overtop...only difference betweeen me and Jaybird is the question about using 6 mil plastic over top the sleepers before installing the plywood subfloor.
The way Jaybird described it is the exact same way as presented in the FHB TOOLS &SHOPS 2002 issue ( No. 160)...article on pages 60 - 63 by Scott Gibson. Mr. Gibson advocated using the poly as a vapor barrier before putting down the plywood. He suggested that any seams in the poly be lapped 6 inches.
Personally, I abhor poly...period. Everything I ever ripped into that was rotten had poly installed directly behind it. I think even putting 6 mil down on the concrete floor before installing sleepers would be a mistake as well. Concrete that stays wet will eventually get moldy, and will crumble. The old timers used to coat concrete flooring with tar and then embed tar paper into that. Nowadays, you could simply trowel on all types of waterproof mastics that are used in damproofing foundations. I'd opt for that if my floor was damp, rather than poly.
This is just my humble opinion only...and probably a lot of posters will not feel the same way as I do...but plastic sheeting has no business ( other than temporary usess) being put into place as part as a final building component...period!
Davo
I`m still a bit leary of poly myself....I wouldn`t be adverse to replacing the layer of poly with a layer of roofing felt.
FWIW, when I purchased my home ten years ago, I renovated the entire thing....all walls and ceilings were opened insulated and polyed prior to a fresh layer of sheetrock. Since then, I`ve made some changes here and there...an addition, a new kitchen..none of the walls I opened showed any problems of trapped moisture....all was as clean as the day I installed. Ten years isn`t an eternity, but it does give me a bit of confidence when I hear of the horrors others have experienced with poly.J. D. Reynolds
Home Improvements
"DO IT RIGHT, DO IT ONCE"