Subfloor water proofing question

[n74tg]

I'm about ready to start installing my 3/4 T&G OSB subfloor.  It will take me awhile to get it in the dry, and I want to protect it from the elements until then.  I have some tarps and visqueen, but I don't think I want to depend solely on those; so am considering some type of a roll-on sealant.  I'm thinking either paint or maybe Thompson's etc.

Anybody got any suggestions both as to methods I haven't considered and products you particularly like.

Thanks
Tony

[John_C]

When I built my house I used Advantec sub flooring.  I didn't have any problem during construction and a few scrap pieces that sat in the weather for about 10 years didn't seem to suffer much either. I'd get the best material I could find and consider the extra cost an investment.

[n74tg]

The subfloor was bought over a year ago and has been sitting in garage storage since then.  I'm pretty much obligated to use it.

[John_C]

Could you spare a small piece say 6" x 6"?  Throw it in a bucket of water and see how it hold up.  Some of the OSB becomes mush pretty quick, some of it seems very durable.  At least you'd know what you were working with.

[MountainDon]

Everyone who's used Advantec swears by it, whereas some others have ended up swearing at regular OSB. But since you already have the OSB and I suppose have no alternate use for it, that'll have to do.

I would not depend on tarps or plastic. Water will always find the pinholes and leak through overlaps. The wind could cause havoc and whip a trap around. Then once the water is under it it gets trapped.

Working with what you got I think the best bet would be painting it with exterior paint. Maybe you could get lucky and find mismatched paint for cheap at a big box store or specialty paint dealer. Maybe interior would work for as long as it would be exposed. I'm not sure of the real differences between int & ext for short term. 

I've never found Thompson's to be as good as they claim. OMMV.

[ScottA]

Paint it with exterior primer or paint. 

[rdzone]

on our project we used plywood t&g.  A common practice up here in rainy areas is to roll on thompsons water seal.  That is exactly what we did, making sure to really coat the seams well the water just beaded up.  We had lots of rain, which rally made me nervous, but no swelling of the decking what so ever.  There were many days once the walls were up but the roof wasn't on that we used the shop vac to suck up gallons of water.


Our first winter we got the deck done, sealed it, put plastic over it then a tarp. No problems what so ever.

Chuck

[Willy]

on our project we used plywood t&g.  A common practice up here in rainy areas is to roll on thompsons water seal.  That is exactly what we did, making sure to really coat the seams well the water just beaded up.  We had lots of rain, which rally made me nervous, but no swelling of the decking what so ever.  There were many days once the walls were up but the roof wasn't on that we used the shop vac to suck up gallons of water.


Our first winter we got the deck done, sealed it, put plastic over it then a tarp. No problems what so ever.

Chuck

I use a hand pump up sprayer to put it on with. It is hard on the pump but there cheap and do a good job of making the coating real thick. Mark

[rdzone]

rolling worked great, since the can said use only a thin coat.  I will say you need to be careful.  If there is just a light rain the newly treated deck can be pretty slick.

[n74tg]

I really like the mismatched, cheap exterior paint idea.  I think I'll go with that...thanks all

[n74tg]

Well I didn't have much luck finding mismatched exterior paint, but I did find lacquer based primer, white, $15 for 5 gallons.  And boy did that stuff roll on good with a nice thick coat.  Best of all it dried in 20-30 minutes.  So far, all I've got done is the two beams.  Right now, am trying to decide if I should do the mudsill and rimjoist.  They're covered right now with plastic, and I think I can just uncover as I go; so It wouldn't be absolutely necessary to paint them. 

Anybody got any good reasons why I should paint them anyway.  I've got plenty of primer; and as slow as this project is going, time is what I have plenty of.

[CREATIVE1]

My son uses marine paint on porches and as an undercoat, and it lasts great.  This is what I might use when we do our house.  The Advantec sounds interesting too, will follow up.

[n74tg]

Okay, next question.  I rolled this stuff on with a paint roller.  It went on about as thick as latex would go on with a roller.  It dried to the touch in maybe 30 minutes and looked great, appearing somewhere between a semi-gloss and a full gloss paint.  After a week, or less, I have lots of cracks in the paint.  In places it looks like it didn't stick to the lumber (new lumber, not pressure treated).  All lumber was dry when painted.

Anybody got any ideas.  I mixed the paint well before painting; used a drill powered stirring paddle. 

Granted, the primer wasn't real expensive; and it did have a lot of solvent (lacquer) in it, because even when painting with it outside and in a light breeze; this stuff was noticeably giving off vapors.  I didn't get high or anything, but if I had been painting indoors I think I would have.

[PEG688]

OSB does not paint well , that's what I think.   Painting OSB is a waste of paint and time. YMMV , but I know I'm right.

[n74tg]

PEG:
This stuff painted was not OSB; it was regular lumber; yellow pine I think. 

[PEG688]

PEG:
This stuff painted was not OSB; it was regular lumber; yellow pine I think. 

Oh you started out talking about OSB didn't you? I just figured you used the term "lumber" meaning OSB , that happens around here most of the time , misnaming things.

What was the real "no $hit" moisture content ?  Dry to the touch is not necessarily "really" dry. I'd guess the wood was wet and the primer just couldn't adhere like it should. 

Of course it could be 40 "other" things that caused it.       

[n74tg]

Anybody willing to share what some of those "40 other things" might be.  But, probably most important to me, is... should I expect anything to be wrong with the lacquer based primer itself.  After all, it was pretty inexpensive. 

I don't think it's a mixing issue.  After all, I did stir it up well. 

Now, possibly I did apply it when it was maybe a little too cool.  I think it was 55 or so when I did some of it. 

thanks

[glenn kangiser]

Possibly not thinning the primer -- for metal such as auto repair we thin laquer primers around 50  to 100% to get it sprayable.

Waxy coating on pine?

[John_C]

What did the instructions say?   Most of the lacquers I've used needed to be thinned and put on in thin coats.  They were sensitive to temperature and to moisture, both in the material and humidity.

[PEG688]

  You never answered the what was the "real moisture content" question yet!

Where was the material when you painted it , outside ? Installed as decking ??

If so was it installed on a post and pier foundation and the ground under it was still very wet ? If so the ground moisture could have had some thing to do with it.

If it was "dry" to the touch can , if it's not installed , cut a end off to look at the inner grain to see if it is wet ? That's IF you don't have a moisture meter to really check the MC of the stock.

  You say Lacquer based , most ,  not all , wood finishing products that are lacquer based are NOT EXTERIOR Rate products.

Oils based yes , water based / latex are exterior use products.

So there's a few more options to look at.

My personal guess is still interior moisture in the stock.       

[n74tg]

Okay, let's see if I can answer some of this.

Real moisture content - I don't have a moisture meter. 
Installation - on top of a concrete block wall, 3 feet above ground level at shallow end, 8 feet above at deep end.  Wood had been installed and covered with visqueen for weeks prior to painting.  Upon removal of plastic, wood was dry to touch; ie no visable or feelable moisture.  If memory serves, I did paint it same day as visqueen removed; in fact probably painted it within 30 minutes after removal of visqueen.
Ground condition - hadn't rained in a week or so, ground not powder dry, but also not muddy.  Walk on it, pick up no dirt/mud on shoes.
Outside humidity at time of painting - anywhere from 30 to 60 percent relative humidity.
Night time temps - on some occasions did go down to maybe 35, but I think not on the night after it was painted.

Now, here's a possibility.  The salesman did say that this primer is the stuff they use to prime wood trim prior to being sold in stores like Lowe's and HD.  In fact, it was bought from a place that manufactures and sells wood trim.  So, it just may be an interior grade primer.  Since salesmen do sometimes lie, he may have lied to me about it's applicability for outdoor use because I did ask.

Any more thoughts?

Thanks PEG for your input; I really do appreciate it.