My local home center has imported underlayment cheap. $10 a sheet. Is this stuff made with waterproof glue? I need material for a porch ceiling. It will be outdoors, but only rarely wet. This doesn’t need to be structural, just hide the joists. Quarter inch thick would be fine. I’ll put some battens on for decoration and it will get a solid stain. My other choices are T10-11 or hardiboard, but I’d just as soon use something cheaper. Any other good options?
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Luan underlayment, if labeled as such is made without voids in the plys and exterior grade glue.....water resistive...not waterproof.
The price "seems" cheap as compared to todays current domestic plywood market, but in just the past 2 years when 7/16 OSB was ~$7.00 per sheet the then $10 per sheet luan was deemed "expensive"! It's all a matter of perspective.
I would feel that 1/4" materials on a ceiling joist at 16" or 24" would "bag" down for the lack of rigidity.
......my preference would be 1/2" u/l grade luan ply for a stiffer/flatter ceiling.
Ultimately paint/varnish will be your first line of defense against humidity and rain....don't for get to backprime and the seal at the edges.
.................Iron Helix
what you said..and 1/2 '' MDO is even nicer for paint.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
According to the Plywood Institute or whatever they call themselves, plywood used for soffit, porch ceilings, etc need not be "exterior" grade, but can be the next grade down in water resistance (which I'm thinking is "exposure 2", but don't hold me to it). Whatever you use should be grade stamped either exterior or exposure ?2?.
As mentioned, the 1/4" would sag and additionally, it will take paint or solid colour stain very unevenly requiring four or five coats to begin to look good. The expense in labour and materials to make this product appear acceptable on the porch ceiling will begin to approach the amt of money it takes to make the ugly ducking in high school look like the Queen of the prom for that all-important photo for the memory album
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I wouldn't have thought it would be too bad to stain, but I've never tried it. Yes, wouldn't be too good to have it sag. An extra hundred in materials will probably be worth it.
I installed 3/8 cdx for my porch ceiling and the moisture had made it buckle. I myself was hoping for some type of PVC panel to go over this maybe ina waincoat style trim.
How about greenboard drywall? I recently repaired a porch ceiling that had this on it. If it weren't for a few leaks in the roof above, it would have worked pretty well.
Al Mollitor, Sharon MA
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The roof won't leak for a while probably, but it will eventually. This porch has a somewhat rustic look. I think I'll check into roughsawn 1x boards next time I get out that way. What I really like is t&g beadboard. A good bit too expensive for this job. But, I'll look around. Maybe somebody has a lower grade thats cheaper. Does not make much sense to spend the time and put up something that won't last a good few years. I'd much rather spend $10 a sheet, but if it won't work fairly well I'll keep looking.
How narrow about T&G cedar siding?
I've used 3/8" beaded plywood on ceilings that weren't wider than 8'. The battens can look a little funky with the beadboard. Might have to put in some blocking, but no sag with framing on 16" centers. Same with 3/8" AC ply and battens, no sag. Don't worry, we can fix that later!
I'll see how the prices work out. T&G would look nice. The ceiling is 9 by 16 or around there. Bigger than a normal sheet will span. Hardiboard comes in 9 x4 sheets. I'm not sure if that's good for horizontal use. For plywood, I'd nail battens every 6 or 8 inches to hide some of the seams. That might keep it from sagging, but maybe not. T&G wouldn't need the battens