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Waterproofing ply


Vijay

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Morning :)

 

I'm sure there was a post about waterproofing normal ply but I've searched and can't find it. Is there any suitable way of waterproofing normal shuttering ply so it can be used outside without coming apart?

 

Cheers

 

Vijay

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You could use a water repellent like Thompsons Water Seal (theres a No Nonsense one too) but what you really need to do is treat the edges and use something to stop the edge delaminating, water getting in and so on. Cheaper plys have holes and gaps along the edges. I don't think the "waterseal" types would do it. Maybe Waterseal the faces and black bitumen paint (or even cheap gloss?) the edges? How many to do? On show as a feature? Maybe something like Sadolin if only one or two and do all faces and edges. I have a feeling cheaper, non WBP plys might come apart anyway through temperature extremes aside from water ingress.

Edited by Onoff
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Is this temporary or permanent ..?

 

most shuttering ply is already WBP anyway, marine ply is just certified to have no voids and the more expensive ones have thinner layers and more of them than cheap ply. 

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temporary, it's for the windows and doors shuttering on my ICF build, but I'm hoping to just re-use a lot a of it for the upstairs windows.

 

This stuff definitely doesn't like water, started to laminate when a slight bit of rain got on the ends.

 

Happy to use water seal and a bitumen paint on the edges if that works but would fence paint work on the faces of the ply instead of water seal, as I have some already?

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I painted some brand new OSB3 with No Nonsense Wood Treatment after putting it on the kids playhouse roof. Unfelted but covered by a tarp since. Sure it softened the glue holding the OSB together as the edges have blown a bit.

 

I'd honestly rather use marine ply than OSB on say the side of my dormer when I redo that. 

 

I know I'll be a lone voice on this!

Edited by Onoff
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44 minutes ago, Onoff said:

 

 

I'd honestly rather use marine ply than OSB on say the side of my dormer when I redo that. 

 

I know I'll be a lone voice on this!

 

Depends what the top coating is - OSB is fine as a backing but not as a final surface, and under lead it can show pattern. GRP and I would go OSB as it’s sealed in and the surface mechanically bonds to the sub structure too

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