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Sealant / Primer for OSB

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Gary_S

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I am going to paint the OSB in my workshop but am told that I need a good sealant / primer. Do you guys have recommendations? What is good value?

Gary
 

Wuffles

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Really? What sort of OSB is it, OSB3 is pretty much waterproof so I would have thought any paint would do. That's what I'm planning anyway, splash of water-based emulsion on it.
 

Gary_S

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Wuffles":35nlw9kb said:
Really? What sort of OSB is it, OSB3 is pretty much waterproof so I would have thought any paint would do. That's what I'm planning anyway, splash of water-based emulsion on it.
It was Wickes general purpose OSB2
 

Wuffles

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It'll drink your paint, that's the only thing I'd be worried about. Don't use a posh base coat :) - again, I certainly won't.
 

RobinBHM

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White emulsion is probably fine.

Ive painted osb3 that way, and its fine. Ive noticed a bit of brown staining coming through, but not enough to worry about.
 

Ali

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Ok treat my words with caution as I haven't done it to OSB but have looked into it for a project once.

What you need to do is use a Latex Primer, I think something like this is suitable but ring up and ask please from wherever you buy in case I have got the wrong product: http://www.decoratingdirect.co.uk/viewprod/z/ZINBE/
 

Wuffles

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I'd use Zinsser Bulls Eye if I had perhaps a metre or two of something I wanted a really good primer on, gets pretty pricey if it's more than that though. Why use a posh primer like that?
 

No skills

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There's a marked different in quality between osb 2 and 3, I had a sheet of 3 out in all weathers for 6 years with no detriment - the 2 I've used on the shed roof that been exposed to the elements for 2 years is cabbage.

I would expect 2 to soak up paint like raw chipboard. Maybe this is the one time in life where somebody says "prime it with pva" (cos that's the universal wrong answer for everything) and it's a good idea????

Obviously try on a scrap first!
 

xtian170174

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How's everyone's OSB performing off the back of this thread?

I have just taken delivery of about 50m² of OSB for workshop roofing and the original notion of torch-on felting is out the window because some of the roof pitches are too steep and sagging/running may result during hot weather...

...What I think will work best is priming & painting the installed OSB, then cladding it in multiwall polycarbonate for complete opacity where required - the thinner PC required with the OSB will make it up to the thickness of the clear stuff used, so it should all come together neatly - but I'm not at all sure about treating the OSB and even after dried what may happen with the PC when affixed to it - check out this chemical compatibility and of course taking into account the possibility of a reaction already taking place with the OSB..., I feel this limits options considerably, but with such a list hopefully being as short as it is exhaustive, I cannot find any useful information to that end - any pointers?
 

xtian170174

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ps
Point to note - I'm considering something along the lines of epoxy resin too, more readily associated with industrial flooring..., open minded going into this as it does not seem like an everyday occurrence, despite seeming like a structurally better and more futureproof solution than all but box profile rigid foam composite panels.
 

Cabinetman

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Never tried painting it, but I used the (Normally used for roofing) tongue and groove 600 mil by 2.4 's 18 mil thick for my floor in the workshop, I used Johnstons floor varnish – two coats and it’s still pretty damn good after 6/8 years. Ian
 

xtian170174

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Never tried painting it, but I used the tongue and groove 600 mil by 2.4 's 18 mil thick for my floor in the workshop, I used Johnstons floor varnish – two coats and it’s still pretty damn good after 6/8 years. Ian
Cheers, I'm awaiting a response from Johnstones', they've recommended Flortred , but a primer will likely be necessary as it's for the roof and all [extra] ways to seal it will be considered - I'm [perhaps vainly] hoping to install & forget - i.e. if it can last as long as the polycarbonate should without issue, that's as much as I could expect...
 

Cabinetman

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Hi Xtian, The Johnstons floor varnish I used was water-based and I wouldn’t recommend it for a roof, what’s wrong with black horrible bitumen out of a tin? That would certainly seal it.
 

xtian170174

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Hi Xtian, The Johnstons floor varnish I used was water-based and I wouldn’t recommend it for a roof, what’s wrong with black horrible bitumen out of a tin? That would certainly seal it.
I think bituminous coatings are possibly bad for polycarbonate - again I'm asking the publisher of the compatibility chart and await their reply as they only list...,
AsphaltD-Severe Effect

...in associated reactions..., ...not something I would take a chance on.
 

xtian170174

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What purpose will the painting serve? If its properly clad why paint it?
I know right - but there's no completely opaque polycarbonate product, the finish is to achieve something complimenting the darkest tint PC sheet [bronze], to see a uniformly dark roof rather than a tan colour board visible under a bronze tint sheet..., which you may say is just an aesthetic detail complicating things and nothing else, and to get over it they way it would look without trying to match for colours - but that's ultimately everyone who sees it, not just me...
 

xtian170174

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[i.e. multiwall polycarbonate - there are solid sheets, but these are not being considered]
 

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