Plywood floors

[flatplane8]

Hi,

 

My new boat has chipboard for the floors, and not surprisingly, this is breaking up in places.

 

I'd like to replace the chipboard with plywood, which I'll then either paint or stain. The floor bearers are about 2 feet apart.

 

From what I can gather 18mm plywood would be about the right thickness, what I'm not sure about is what type of plywood to use.

 

For a 8x4 sheet, 18mm thick, the price can vary from low £20s for spruce or softwood ply, up to £70 for birch ply.

 

Are all these plywoods suitable from a strength/structural point of view, and the higher cost is for a higher quality finish, or are there other differences?

 

I'll need about 23 sheets, so the total cost is of interest. Having said that, if a more expensive material is justified, that'll be fine

 

Thanks,

 

Simon

[John Orentas]

There is another option Simon, what was close to being a standard at one time was 18mm 'Shutter Ply', as it's name suggests it was made for shuttering of wet concrete so was totally waterproof and structurally strong.. Of course it can only be used if you are planning to cover it in some way, on it's own it looks bloody awful.

 

Very low cost, and not much more than half the cost of the pretty stuff.

Edited May 16, 2008 by John Orentas

[blackrose]

The best thing you can use is marine ply but it's damned expensive and I'm not sure if it's really justified. Others will have a better idea. I've heard that ordinary shuttering ply is not recommended as it can delaminate.

[smileypete]

Hi,

 

My new boat has chipboard for the floors, and not surprisingly, this is breaking up in places.

 

I'd like to replace the chipboard with plywood, which I'll then either paint or stain. The floor bearers are about 2 feet apart.

 

From what I can gather 18mm plywood would be about the right thickness, what I'm not sure about is what type of plywood to use.

 

For a 8x4 sheet, 18mm thick, the price can vary from low £20s for spruce or softwood ply, up to £70 for birch ply.

 

Are all these plywoods suitable from a strength/structural point of view, and the higher cost is for a higher quality finish, or are there other differences?

 

I'll need about 23 sheets, so the total cost is of interest. Having said that, if a more expensive material is justified, that'll be fine

 

For ply I'd look first at exterior/WBP (weather and boil proof) ply, shop around and have a look at it before purchase. Also check it's the right stuff by boiling(!) an offcut.

 

I'd prefer T&G floorboards though, gives more options eg bare floor & area rugs. If on a tight budget then OSB (oriented strand board) is worth a look.

 

Whatever is used I'd make sure it gets a coat of woodstain (not dye!) that's breathable/'microporous', on all sides and edges before fitting.

 

cheers,

Pete.

[Ex- Member]

The best thing you can use is marine ply but it's damned expensive and I'm not sure if it's really justified. Others will have a better idea. I've heard that ordinary shuttering ply is not recommended as it can delaminate.

 

 

Yeah shuttering ply only needs any water resistance for a short time whilst concrete sets, it doesn't have any specific water resistment treatment other than being WPB. It can laminate after time as Blackrose mentions as it's not designed for long term use, it's a short term product really used to form concrete. What I would advise is a 18mm ply with a good finish on the up side and some hardwood layers. If you intend to lay other flooring on top which most people do, having the smooth flat surface makes life a lot easier. We used Hardwood WPB ( Water & Boil Proof) Plywood currently around £28 a sheet now from B & Q there's an offer on in some stores to buy 2 sheets for a cheaper price btw.

Shop around though for quantity.

 

You can treat the underside with a decent wood preserver, not creosote it will stink for ages. We also treated the 3x2 bearers in the same stuff. You can use the softwood but it's only a bit cheaper so just as well use the hard. This is plenty strong enough especially on 3" bearers. Standard quality builders ply will suffice also, usually comes from the far east, or called far eastern ply. Prices have shot up a lot over the past 5 years, I recall paying £17.00 a sheet for 20 sheets just 4 years ago. I think Marine ply is around £60 a sheet, and a bit ott for a floor, unless you're loaded of course LOL

[Mac49]

I've had some pretty good WBP which was from Malaysia or Indonesia recently, it's got at least one good face on it and is much better than the Chinese stuff which seems to have voids in it and be a bit bendy, a specialist plywood place should keep a few different grades in.

Rick

[Ex- Member]

I've had some pretty good WBP which was from Malaysia or Indonesia recently, it's got at least one good face on it and is much better than the Chinese stuff which seems to have voids in it and be a bit bendy, a specialist plywood place should keep a few different grades in.

Rick

 

I bought a sheet of 18mm a few weeks ago from local merchant, cut it up as required and the lamination was pitiful, i ended up filling all the edges with body fillerdue to wide open spaces everywhere, there were also some areas where it was bumpy ie laminate overlapping. Really annoying. Contacted local B merchant where I got it, and you're right, came from China, far eastern is in short supply they reckon. More like more expensive me thinks

 

When you buy plywood look at the edges, manufacturers use filler in the edges to hide any gaps, the filler is a creamy colour, so lots of creamy edges means lots of gaps

[flatplane8]

Thanks all, I've done a bit more digging around, and interestingly enough the only plywood I can find that specifically says its for structural use is spruce ply. Some more information here.

 

My initial plans are to stain or paint this floor, so a reasonable finish is needed. I'm thinking about this 'faux-plank' effect as described here

Edited May 16, 2008 by flatplane8

[kingfisher]

Thanks all, I've done a bit more digging around, and interestingly enough the only plywood I can find that specifically says its for structural use is spruce ply. Some more information here.

 

My initial plans are to stain or paint this floor, so a reasonable finish is needed. I'm thinking about this 'faux-plank' effect as described here

yep thats the right ply to use ,we fix battens at 400 centres and screw at 400 centres .

using it to make a faux plank effect may not look right to the eye probably to many screws but painted would make satifsactory job .you should be able to get it for around £20 sheet ,but go and view it before buying as stated there are different grades i cant remember which is which(to much wine ) our local timber yard harlows in derby have wisa spruce if that helps

[hardastern]

What is the best preserver to use - I plan to line my old 18mm floor with 3.5mm ply to give a surface smooth enough for floor covering (probably vinyl planks)

 

What should I treat the ply with please?

[David Mack]

I'll need about 23 sheets,

 

23 8x4 sheets?? What size of boat is this?

[smileypete]

What is the best preserver to use - I plan to line my old 18mm floor with 3.5mm ply to give a surface smooth enough for floor covering (probably vinyl planks)

 

What should I treat the ply with please?

I'd just give the ply an overall coat of paint or protective wood stain, including edges and back. If it still gets wet enough to rot then there are probably much bigger problems!

 

cheers, Pete.

~smpt~