water proofing your wood

[atahoekid]

I'm having trouble balancing the desire to have waterproofing under the fiberglass in case it cracks against the unknown of how well the resin will adhere to the varnished wood.

Anyone have some experience they can share on this?

IMO I'd be more inclined to fiberglass the edges then use the varnish. When building kayaks, I know you can varnish over epoxy but I'm not sure if you can epoxy over varnish. I know you were thinking about polyester resin but it's probably the same

[angib]

What is the general thought on which one to do first?

Definitely put nothing under the fiberglassing - whatever you put there reduces the adhesion.

And in a general point about wood protection, the thing most people don't seem to realise is that everyone has completely different standards about how much coating to put on - so what one person says works may not work for someone else, because they only put on a quarter as much of it. Thickness of coating is at least as important as what coating material you use.

I always remember the epoxy-wood boatbuilder I used to work for who said "epoxy resin is varnish that can be applied six coats at a time".

[GPW]

When waterproofing , More is better !!! ^ Can’t argue with a boat builder ...

When using “the mix" we apply as many coats as possible , or until the wood will no longer accept any more ... just pools on the surface ... Thinking the “theoretical ideal “ would to be to totally encapsulate every fiber of the wood , eliminating any chance of water intrusion ...or the dreaded Rot ...

Fiberglass can be laid over most anything (within reason ) as long as the underlying surface is “prepped" properly , which usually involves much sanding and cleaning ... For trailer building , I could see/understand waterproofing under fiberglass , otherwise , if the glass cracks , the literal “sponge" of untreated wood anxiously awaits the water intrusion ( we’ve seen much of that on older FG boat transoms ) ... You would have to wait for the first surface preparation to totally cure , and then re-sand (tooth) and de-grease , before applying the glass ... Lots of work , Yes , but then you’re ... “protected” ...

Ps. It’s always BEST to use fully compatible products ... read the can ...

[angib]

Some people take a pride in seeing how far they can make a brush's or roller's worth of coating spread - which is the exact opposite of good practice, which is to apply as much product as you can without runs. Unless you're going for a really fine varnished finish when many thin coats and some light rubbing down in between give the best result. But then in this context 'many coats' means at least into the teens and maybe into the twenties.

I'll be the heretic and say that any product with solvents in it will always be a second-best waterproofing method. When those solvents evapourate, they will leave behind little voids that can allow moisture through. And I'm quite unconvinced about the benefits (except possibly psychological) of 'soaking in' - I think what is needed is as thick as possible a water-resistant surface layer above the wood and having the water-resistant layer in the wood is not as good.

[GPW]

I believe in the foamie' world , wood is used to a minimum and mostly for floors , door and window frames ... or generally as little as possible , and those pieces should have some kind of waterproofing , one would think , given the unlikely possibility of a skin failure ...

[ghcoe]

Choosing Between Oriented Strandboard and Plywood

Good article on the differences of OSB and Ply.

http://bct.eco.umass.edu/publications/b ... d-plywood/

From this article it seems that if you cut OSB that you should treat the cut edges (paint or mix) to prevent edge swelling. That is why the edges are painted at the factory. Good to know just before I start my floor.

One question though. If you use this mix will it cause a paint bonding issue if you plan to paint over it later?

[GPW]

GH, Thanks , that was a good read and certainly reassuring !!! Good to know about that Edge thing' ....

We’ve painted over many surfaces treated with the mix , either oil or Latex , no problems ... the plan is to use the mix on my OSB floor too !!!

Just from experience , when I had a commercial RV trailer , the floor was made out of some kind of cheap “sawdust” board... soaked up water like a sponge and immediately turned to Oatmeal ... Repair areas , treated with the mix , became quite waterproof .... a step that should have been done by the manufacturer...

[davidc]

I just painted over "the mix" with primer and then exterior latex, and had no issues with bonding. One tiny frustration in certain parts where I had super-smooth areas (body filler covered in glazing putty) that was sprayed with the mix was that the primer "beaded up" (not quite the right description, but there was some sort of surface tension thing going on) to create a couple pea-sized unprimed areas. A second covering of primer in those areas took care of it easily.

The only issue I did have related to "the mix" is that glue is less likely to stick to it. I used the lowest-end PL Premium glue, and it popped off the side with many coats of mix. I then used the 8x strength PL Premium, and it seemed to stick much better with that. If you build completely first and then waterproof later, I don't expect you would have any issues

[ghcoe]

Good to know. Thanks.

[lthomas987]

Has anybody made the mix with "odorless" mineral spirits instead of the regular sort?

I am getting domestic complaints about the smell of my garage. The complaints might be worth the extra couple bucks.

[GPW]

L’ I tried some odorless paint thinner, turns to be some kind of milky soapy stuff ... not good ... Not good for the Mix ... Best just hook up some kind of exhaust fan , and assure the domestic complainers that it will all be done quickly ...

[rebapuck]

I'm about to have the rotted bottom of my casement windows repaired. I can use this on them before painting right?

I've read the thread and I'm confused. Oil or water based poly? Please write the recipe again.

[GPW]

Oil based Polyurethane varnish , 25% , Mineral Spirits , 75% ... paint on till it won’t take any more (multiple coats ) ... let dry well, then prime and paint as normal ...

[rebapuck]

Thanks. I can use latex over dried waterproofing?

[GPW]

Yes ... A good primer is suggested first ..