Plywood outside

[DiscoStu]

I am keen on using some plywood to make an outside bench. I want to use ply because I want to cut strips and stick them together to get all the stripes and make a feature of them.

However I am concerned about using ply outside. Are there any good oils that I can use that will enable it to survive outside? I appreciate it may need a few coats! I don't really want a shiny finish so not to keen on a glossy varnish.

 

[jumps]

It's all about the ply...what it's laminate from, the adhesive used in it's manufacture and the processing itself. Once upon a time you would just purchase 'marine ply' from any supplier and expect some chance of success - but it never seems quite that simple any more!

After that you are left with the usual wood treatment issues.

 

[Phil Pascoe]

Even if you find proper marine ply (and it's unbelievably expensive) it's not designed to be left with that amount of end grain left open.

 

[gavinr]

i use quite a bit of marine ply and there is marine ply and there is marine ply. once upon a time i was even sold some that went mouldy almost overnight, suffice to say that was an interesting chat with the supplier and they definitely got no more of my business.

i would be honest, from my experience, marine would not be my first choice for an outdoor bench but if you want to bend then yes it would be easiest.

the very good stuff would be a must, if you want natural oil then danish would be ok, varnish better and the one i like if i have to use some is 'le tonkinoise' which is well revered in boat circles.

decent ply is also costly. depending on thickness, lets say 12mm, at least 85 ex vat per sheet. you definitely need to track down a marine specialist supplier not your local b&q.

 

[Newbie_Neil]

As jumps says it used to be easy buying marine ply. You need to look for "Marine Plywood to BS1088". There is also "Marine Plywood Lloyds Approved", but this will cost a small fortune.

I would recommend Le Tonkinois Varnish. This is an excellent product and can have a matt finish.

HTH,
Neil

 

[DiscoStu]

I want to use ply because of the look. I might have a little play with some and leave it outside and see what it looks like.

 

[AES]

DiscoStu:

Back in "the good old days" it was also possible to get ply used for shuttering. As it is/was used to support concrete while it dried it was "waterproof" without any treatment for at least a couple of days, and when I worked as a labourer on building sites (at least 40+ years ago!) it was often used more than once. And it often had at least one good side too.

Now I am most certainly NOT an expert, especially not as far as modern materials are concerned, and I do not work in the trade at all, but perhaps others here with more knowledge than I could offer some comments on such ply today - it used to be quite a bit cheaper than "real" marine ply, and if you're going to protect it anyway, it MAY be a possibility for your bench?

Krgds
AES

 

[No skills]

Are these for a customer or yourself?
If there for you then ld consider these benches as perishable items that might need replacing every few years. For the money you will have to spend on some very good marine plywood you could easily make them several times over from cheaper stock.

With a bit of care and plenty of finish I think they would last longer than expected even from cheaper ply.

Imo

 

[jumps]

there are some interesting angles coming up here - interesting in that they are quite divergent.

personally if I was doing a labour intensive project such as a garden bench, and had decided to use ply for the aesthetic impact ( I fully understand this as I make rocking horse chairs in both ash and ply with the latter looking more stunning!) then I would want the damn thing to last for ever!

given the reduced expansion/contraction of ply in the first place I would probably look to encapsulate the thing in a 2 pack clear coating and bring it in in the winter etc...

I've also just done a number of Owl/Kestrel bird boxes in a medium priced ply then well treated (2 coats Sadolin's Classic/2 coats Extra) but here the use of cheaper materials is consistent with ease of manufacture - 1 x RAS, 1 x brad gun and glue - means that the treatment becomes the cost in terms of labour!

then again I suppose I can also see the argument that the labour side is the enjoyment element rather than the cost (or sitting on the bench!)

interesting.

 

[DiscoStu]

This is for me and I'm not against replacing in a few years as I'll probably want something different then. So assuming I'm going to use some cheap ply: what's the best options for giving it some longevity.

 

[Phil Pascoe]

Prayer.

 

[kostello]

Coat with epoxy.....?????
It's not a brilliant idea imho

 

[wizard]

the house next to me have a compost bin made from shuttering ply it was there when I moved here 20 years ago and it's still there

 

[No skills]

I've got raised plant beds made from 12mm shuttering ply and timber frame that are fine after 5 years so far. No delamination. If you make some effort with the treatment it will help.
Interestingly I have some bits of wbp ply that have sat round doing nothing that are coming apart.
Dont forget that cheap ply will have the odd void here and there that will show on the edge. Will need to be filled obviously as this is where delamination will start.

Epoxy would be good but spendy. As this is a 'temporary' project (years not decades) I'd try loading it up with an outdoor polyurethane, lots of coats.

Again all imo. Nay sayers say nay and all that..

 

[DiscoStu]

I do understand people's concern and "prayer" did make me smile. It is only for myself and if it doesn't last then so be it.