I have vertical grain fir tongue and groove boards for a screened-in porch floor. The deck has “Advantech” 3/4 inch T&G subfloor over 2×8 joists 16 ” OC 12 foot span. Originally the porch deck was going to covered with frost rated tile but we decided that the framing was inadequate to provide necessary stiffnes for this type of floor. Therefore I wound up getting the fir. The floor joists run parellel to the direction that the fir will be installed.
The edges of the deck definitely will get wet secondary to rain etc. The deck is sloped about 1% from the house.
Can I nail the fir down directly to this subfloor? Do I need to have some type of airspace between the subfloor and the fir? Is tar paper between the fir and subflor adequate? I was planning on covering the edges with some type of peel and stick membrane to protect them. Could a waterprroof membrane be used over the entire subfloor?
Any thoughts would be greatly appreciated. This is being done in the northeast(central new york).
Replies
If you have elevation enough to run sleepers to provide a weep and breather space, I would definitely do that.
i've had a few experiences with similar done by myself and others over time.
Definitely seal up all six sides and the grooves before you install it. On one of these, I had laid the fir over bituthene at customer demand and presealed it like this and projected that it would last about ten years.
ten years to the day almost, I was back replacing it, with more learned - another contractor had added to this deck and had not done any presealing. his work was about 3-4 years old and was rotting and turning to swamp muck under the coat of paint on top. Mine - right5 adjacent had some rot spots - maybe five percent of the area i'd done.
If I'd used sleepers, I'm fairly sure that it would have done better.
on a few other spots like stairs and landings and small porches without any subfloor, I have also used gorilla glue in the T&G joints. This is a waterproof ( more or less) glue that helped keep water from leaking thru to the underside spaces which were storage fro lawn mowers, yard tools, propane tanks, etc, etc
So faced with your situation, I would do the ice and water on the advanteck, or paint it a couple coats with polyurethene paint. Then run sleepers, then the CVG T&G fir after presealing it, and use gorilla glue in the joints.
One more thing you don't mention clearly, but I would definitely plan it so the grain of the T&G is running down slope. If you run across the direction of water runoff, it will cut the lifespan in half.
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Thanks for your response. I have sealed all six sides already. The boards are running with the slope.
Any suggestions as to the height of the sleepers?
Thanks again.
as big as you have room for...3/4" would be nice..
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according to statistical analysis, "for some time now, bears apparently have been going to the bathroom in the woods."
"Any suggestions as to the height of the sleepers?"six inches or so;)3/4" will bne a big help.Fact is, you are doing a compromised system from the start. Allow the 3/4" with drainage weeps open and keep the top sealed or painted every couple years.
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The other thing is to not put them in too tight. The stuff is definitely going to expand in wet weather, vg or not. Allow for it.