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I have a question about moisture control. I looked at a job that has a five year old fur. 3/4″ t&g deck boards . Its on a front porch covered with roof , sits on foundation with 9′ high crawl space below. Two vents in one at each end of masonry . The ends of some boards are rotted, others are getting there, some places the damage heads right back to the house wall. My thought is the water getting past the T&G also in from the end , but then maybe sitting on the tarpaper that was install across the joist five years ago to fix the problem.
First off I can change the location of the berry vine hanging across the front, that’s water control. But while I am there fixing, should I change the vapor barrier from tarpaper on top of joist right under flooring , to 6 mil plastic on earth 9′ down . There is no access so best time is with some flooring ripped up. I can add extra vent holes , have the surbs cut back to get some air around and though. Thanks Robert
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Well Robert, I do a lot of porch repairs, and yours sounds like it has a couple of the more common problems.
First, cut back the vines, and any other landscaping that touches or hangs over the flooring. Nothing like overgrown landscaping to help rot out woodwork faster.
Second, more vents would probably not hurt, however, dampness from below is probably not causing the rot along the ends that you're seeing. Usually dampness from the crawlspace (especially from 9' below) only causes the t&g boards to cup because the underside is damper than the top surface.
Third, I assume the tar-paper-on-the-joists you mention is strips of felt laid over the top of each joist in an attempt to protect them from water which penetrates the flooring surface. That's an old and pretty common practice that you should probably duplicate during the repairs.
Fourth, I would check to see if the porch floor slopes away from the building. You need at least an 1/8" slope per foot of porch floor so that water won't just puddle and lay on the flooring.
Fifth, when you replace the damaged flooring, try and stick with the quarter sawn fir (or maybe mahogany or cypress if available in your area. Resist the urge to use lesser woods like southern yellow pine or spruce because they will not last.
There are different theories about pre-priming the flooring before installation. I don't usually do this. I've seen 150 year old porch floors that are still in good shape which had no primer except the one coat on the top surface before it was painted.
One other detail which helps at the ends. After you install the flooring, trim the ends even (I usually just cut against a chalked line with a circular saw). Then, sand the endgrain on all these ends smooth. Use a belt sander, followed by a finish sander to at least 100 grit. It makes for a better paint job.
Finally, if you take a router and round over the ends of the cut flooring top and bottom until you have a full-round bullnosed end, then sand smooth, you'll get an even nicer looking job, which will shed the water a little better than a square cut end.
And don't use cheap paint. Period.
*Jay , thanks for the reply. Makes sense, It may be syp flooring. I'll use fir for the repair. The tarpaper is beening used as a vapor barrier, covering joist and joist space 100% . Do you think this is a problem ? Now is the time to cut it out from underneath (no access) leaving strips ontop of joist. Thanks Robert
*If the paper is "draped" over all the joists, including the spaces between the joist, then, yes, I think it's a problem. All it'll do is hold any water that penetrates the flooring.Cut it out so that you only end up with strips of felt about 3-4 inches wide covering the tops of the joists.
*Um, wanted to ask if the caller meant 9", not 9', CRAWLspace (unless this house is Paul Bunyan's). At that height, would you do anything about ground moisture?Anyone see "This is Spinal Tap?" The Leprechauns?