woodwork protection

[ChrisL]

Ok can I get some advice on wood preparation, should I be sealing the underside of the floorboards on my sail away if so what is the best treatment I should be applying to the plywood, would a marine varnish be best?

 

same question for the side cladding wall panels 

 

thanks 

[MtB]

35 minutes ago, ChrisL said:

Ok can I get some advice on wood preparation, should I be sealing the underside of the floorboards on my sail away if so what is the best treatment I should be applying to the plywood, would a marine varnish be best?

 

same question for the side cladding wall panels 

 

thanks 

 

 

Not worth the effort in my opinion. 

 

 

[matty40s]

8 minutes ago, MtB said:

 

 

Not worth the effort in my opinion. 

 

 

That depends on the quality of the plywood he is buying, there is some seriously cheap and rubbish stuff on the market now which needs some additional protection straight off the lorry.

[MtB]

3 minutes ago, matty40s said:

That depends on the quality of the plywood he is buying, there is some seriously cheap and rubbish stuff on the market now which needs some additional protection straight off the lorry.

 

I've never seen any visible treatment present on the underside of the plywood flooring on any of the NB I've ever had occasion to take the floors up on. And they never seem to have suffered from the failure to treat.

 

 

 

[matty40s]

6 minutes ago, MtB said:

 

I've never seen any visible treatment present on the underside of the plywood flooring on any of the NB I've ever had occasion to take the floors up on. And they never seem to have suffered from the failure to treat.

 

 

 

Most quality builders PVA coated ply before floorboarding, not something you would notice, but something you would eventually find out, especially if you had a bilge fill with water for some reason.

 

[LadyG]

The cost is tiny compared to the benefits. Not varnish.

Have a look at the Sadolin range . I would always ask for technical advice from people who sell the stuff. If they don't have good technical advice find someone else .

To do my cabin sides i primed, two under coats, sanded, topcoat with Zinser, tough stuff. 

 

Edited July 6, 2023 by LadyG

[David Mack]

I would be minded to use up all the spare part used cans of oil-based paint which I have left over from previous decorating jobs. For the underside of the floor boards and back of the lining panels it won't matter what colour they are, or if the paint has gone a bit gloopy or got lumps in it.

[blackrose]

4 hours ago, matty40s said:

Most quality builders PVA coated ply before floorboarding, not something you would notice, but something you would eventually find out, especially if you had a bilge fill with water for some reason.

 

 

Isn't PVA water soluble? 

[frangar]

The underside of my floor was painted with what looks a lot like bitumen….40 years later it seems to still be working! 

[RAP]

I use Screwfix yacht varnish. Two coats, first coat thinned with white spirits, about 70% varnish and 30% white spirits, and the second coat neat varnish. This is applied to the backs and edges of all ply wood floor boards and plywood cabin sides. 

[David Schweizer]

7 hours ago, blackrose said:

 

Isn't PVA water soluble? 

 

Only when it is still in useable condition. When dry all pva gues will resist moisture up to a point, but to be certain use a water resistant type. I use Titebond 11 Premium, which is water resistant, not cheap or easy to find, but much better than the usual DIY pva glues.

 

Added to warn: No wood glues (including PVA) will resist a constantly wet environment if applied to a porous substrate, such as wood.

 

 

Edited July 7, 2023 by David Schweizer

[Bee]

I wouldn't bother except to say that if one side of wood is painted and therefore mostly sealed the other side can adjust to the ambient humidity and could warp / bow / cup and generally make a nuisance of itself. I doubt if ply will do this but t&g could. If you don't mind extra work I would make sure you have removable sections of flooring to get at whatever is lurking under the floor.

[Tonka]

19 minutes ago, Bee said:

I wouldn't bother except to say that if one side of wood is painted and therefore mostly sealed the other side can adjust to the ambient humidity and could warp / bow / cup and generally make a nuisance of itself. I doubt if ply will do this but t&g could. If you don't mind extra work I would make sure you have removable sections of flooring to get at whatever is lurking under the floor.

I'd be more worried that the stuff that you treat the underside of the ply with will seal it and not allow any moisture to go through from the top thus trapping moisture into the board. Which is why it is not a good idea to apply something to the ply floor underneath a caravan

[TandC]

Coating the underside of the plywood is a job that takes an hour or two to slap on - costs very little in the big picture - and while some may say it's not worth it, why wouldn't you... 

 

I just did the underside of my 25mm ply (external grade) floor with Leyland Floor Paint from Screwfix.  Oil based, it's thick and durable.  I rollered one thick coat on the underside and again on the topside once the floor was laid to give it all a seal.   Also - gave it a good paintbrushing into all the edges, which is probably more important as a sealant.

 

One large 5lt tin was more than enough for 45ftx10ft floor underside.  I needed a bit more to also get the top side done too. 

On 07/07/2023 at 00:31, David Mack said:

I would be minded to use up all the spare part used cans of oil-based paint which I have left over from previous decorating jobs. For the underside of the floor boards and back of the lining panels it won't matter what colour they are, or if the paint has gone a bit gloopy or got lumps in it.

I also did exactly this on another boat - good way to get rid, cost zero and there are always friends with a few tins leftover in the shed.   

Edited July 11, 2023 by TandC

[Ronaldo47]

On 07/07/2023 at 08:50, David Schweizer said:

 

Only when it is still in useable condition. When dry all pva gues will resist moisture up to a point, but to be certain use a water resistant type. I use Titebond 11 Premium, which is water resistant, not cheap or easy to find, but much better than the usual DIY pva glues.

 

Added to warn: No wood glues (including PVA) will resist a constantly wet environment if applied to a porous substrate, such as wood.

 

 

Aerolite 306 wood glue is strong and waterproof. I don't know if it is still available though. I got my last pack from Axminster Tools a few years ago.. I have been told that the original Cascamite is waterproof , but haven't tried it myself.

[David Schweizer]

2 hours ago, Ronaldo47 said:

Aerolite 306 wood glue is strong and waterproof. I don't know if it is still available though. I got my last pack from Axminster Tools a few years ago.. I have been told that the original Cascamite is waterproof , but haven't tried it myself.

 

You are correct Cascamite is waterproof, ironic as is a white powder which you mix in water. I haven't used it in years, and gave my last tin to a friend who was repairing a wooden Sash window. Aerolite 306 is still available but is twice the price of Cascamite.