Advice about plywood please

[starman]

I need some birch ply for my interior refit but as there’s no ‘proper’ timber merchant near me I have to order some in. And I’m really not sure what to order - there seem to be variations on grades, on structure from birch outer skins only to all birch and obviously on price.  Doesn’t help that the grade system seems to have changed too. 

Can someone steer me through - I want stuff that can be painted, and cut and shaped without exposing internal holes. 

[Tony Brooks]

I don't think birch is very durable in damp conditions so ensuring all faces and cuts are well protected would be good (happy for the timber experts to tell me I am wrong, I may be thinking of beech). As a minimum I would want WBP (water & boil proof) glue for interior boat use.

 

Although probably pricey I doubt you will go wrong with Robbins of Bristol - http://www.robbins.co.uk/index.asp

Edited April 13, 2019 by Tony Brooks

[Murflynn]

Birch ply is almost universally used for high quality joinery (typically shop fitting and the like) because it has many very thin layers and is a hardwood, as a result it is very stiff, and can be cut with great precision; effectively it is an 'engineering material'.   As TB points out, it is not designed to be weather/waterproof, so it needs a good protection layer.  When I have used it I gave it 2 coats of epoxy resin - the first one leaves it rough, a light sanding after it has cured, then a second coat which leaves it smooth and glossy.

 

You need best quality birch ply - my local merchant is Robbins, they will sell you a quality product.

 

For carcassing and bulkheads I would use it in preference to marine ply.  I would only use marine ply for external work and for the floor.

 

PS: I would not try to economise on material like plywood.  I once made the mistake of buying marine ply from Lathams at half the price of Robbins.  Some of the sheets fell apart while I was cutting it (serious delamination).  In their defence, they did warn me that it bore a BS1088 stamp but no Lloyds approval, and that the BS1088 stamp is widely abused by foreign suppliers.

Edited April 13, 2019 by Murflynn

[dave moore]

I use birch for cabin doors, stools etc. The advantage is that there are no voids in the endgrain to need filling and sanding. Local boat fitters sell me the odd sheet that I need, saving a few bob...

[Cheshire cat]

I have a wooden pigeon box on my roof  which I always bring in for the winter. I cover the hole with a wooden cap.

 

Last year I made a new cap from oak and ply and painted it with enamel gloss paint. Despite this it has completely delaminated over the winter and is now scrap. 

 

I know the interior is not as harsh an environment but I'd go with marine ply. 

[Chris Williams]

My bridging pontoon which became the hull of my first boat was made of plywood.  It was thirty years old when I bought it and I had it for another five years.  Originally it was painted in Army green paint.  I stripped that and applied Bitumen.  No trouble with delamination, rot or anything else.

Does modern plywood not last as well as that produced during the war? 

[Boater Sam]

Even so called marine ply is not what it used to be.

For external use I now use Buffalo Board and seal all edges with epoxy.

If it is not cabinet work OSB is the most durable but you need to veneer to get a fair face. The stranded finish can look quite modern painted.

[starman]

I’m not doing any external work, just lining out inside and building a back cabin. TBH if it gets wet enough inside to delaminate the ply I’ll be worried about more than having picked the wrong wood?

[stegra]

Is it going to be painted? If so, moisture resistant MDF could be suitable. 

[Bee]

Io its for inside I'd use plasterboard... but seriously, birch ply is awfully dear, it tends to be used for good quality work, patternmaking, stuff like that. I'm not too sure if its really suitable for boat work. Exterior ply has waterproof glue and that counts for a lot. If you're going to paint it then it really doesn't matter what wood is used for the laminates. I would just use exterior ply and be done with it. Moisture resistant mdf?  I don't suppose mdf is anyones favourite material but if the edges aren't soaking up water and you don't inhale the fine dust when cutting it then it should be perfectly ok. My boat is arguably drier than my kitchen at home and I wouldn't dream of using anything other than MDF or chipboard for the cabinets in the kitchen.

[David Schweizer]

6 hours ago, Tony Brooks said:

I don't think birch is very durable in damp conditions so ensuring all faces and cuts are well protected would be good (happy for the timber experts to tell me I am wrong, I may be thinking of beech). As a minimum I would want WBP (water & boil proof) glue for interior boat use.

 

Although probably pricey I doubt you will go wrong with Robbins of Bristol - http://www.robbins.co.uk/index.asp

Birch timber is strong, durable and waterproof, so the sutability of Birch Ply would depend upon whether the glue is waterproof. Beech is not waterproof.

Edited April 13, 2019 by David Schweizer

[Murflynn]

1 hour ago, Bee said:

Io its for inside I'd use plasterboard... 

err ........   really ??    did you omit a smiley in there?

[Bee]

1 minute ago, Murflynn said:

err ........   really ??    did you omit a smiley in there?

Yes,! I think I did, sorry everybody. Actually I have seen plasterboard used, in a big old barge, it was OK but I don't think its quite up to the job.

[Guest]

I bought WBP ply for boat the floor some 15 years ago. It is now falling apart owing to condensation, especially in the bathroom, and I look forward to the day when I have to try and replace it   The MDF bulkheads have been fine. 
Many years ago we built a cabin on a little GRP boat with WBP and it lasted for several years even exposed to the elements, which leads me to suspect that plywood aint what it used to be.

[Boater Sam]

I cannot rate OSB highly enough for boats, it survives in the buff outside very well.

I will not tolerate any structural chipboard or MDF on my boat, the only MDF piece is a turned stand for the coal hod to protect the oak floor. Its all its fit for.

[ditchcrawler]

9 minutes ago, Boater Sam said:

I cannot rate OSB highly enough for boats, it survives in the buff outside very well.

I will not tolerate any structural chipboard or MDF on my boat, the only MDF piece is a turned stand for the coal hod to protect the oak floor. Its all its fit for.

I used MDF for the deck head on my boat, routed to look like T&G and then painted white. The only problem is if you need to fix anything to it, its not as good for fixing to as plywood.

[starman]

32 minutes ago, catweasel said:

I bought WBP ply for boat the floor some 15 years ago. It is now falling apart owing to condensation, especially in the bathroom, and I look forward to the day when I have to try and replace it   The MDF bulkheads have been fine. 
Many years ago we built a cabin on a little GRP boat with WBP and it lasted for several years even exposed to the elements, which leads me to suspect that plywood aint what it used to be.

This was part of the point of my initial question - WBP is no longer an adequate definition for a plywood; in fact strictly speaking it’s not even an industry definition at all. There appear to be  numerous different grades of WBP as well as some of dubious origins. Cut a sheet of ply now and you’ll likely expose voids and patches. Only decent birch ply seems immune (plus proper marine ply).

i wouldn’t have a problem using water resistant mdf inside - I’ve used it with success in domestic bathrooms and kitchens but it’s heavy and doesn’t have much rigidity so I don’t want to risk it on my sloping cabin sides. Also I prefer the feel of wood, even painted. 

Edited April 13, 2019 by starman

[Guest]

13 minutes ago, starman said:

This was part of the point of my initial question - WBP is no longer an adequate definition for a plywood; in fact strictly speaking it’s not even an industry definition at all. There appear to be  numerous different grades of WBP as well as some of dubious origins. Cut a sheet of ply now and you’ll likely expose voids and patches. Only decent birch ply seems immune (plus proper marine ply).

i wouldn’t have a problem using water resistant mdf inside - I’ve used it with success in domestic bathrooms and kitchens but it’s heavy and doesn’t have much rigidity so I don’t want to risk it on my sloping cabin sides. Also I prefer the feel of wood, even painted. 

Yes the WBP floor is full of voids. The stuff I have is the work of the devil, but as you suggest it may vary. Green chipboard would likely have been better than the stuff I have.
I agree and wouldn't use MDF on the linings either. It was OK for internal bulkheads but nothing else really.

Edited April 13, 2019 by Guest

[LadyG]

17 hours ago, Bee said:

Io its for inside I'd use plasterboard... but seriously, birch ply is awfully dear, it tends to be used for good quality work, patternmaking, stuff like that. I'm not too sure if its really suitable for boat work. Exterior ply has waterproof glue and that counts for a lot. If you're going to paint it then it really doesn't matter what wood is used for the laminates. I would just use exterior ply and be done with it. Moisture resistant mdf?  I don't suppose mdf is anyones favourite material but if the edges aren't soaking up water and you don't inhale the fine dust when cutting it then it should be perfectly ok. My boat is arguably drier than my kitchen at home and I wouldn't dream of using anything other than MDF or chipboard for the cabinets in the kitchen.

I had chipboard kitchen cabinets once [unknowingly], they delaminated. My bath panel was mdf, it soaked up water then disintegrated. 

I would never compromise on  quality products in any work. The labour costs are well outwith the cost of materials.  I'd rather use a paper based product than plasterboard in a boat! Not plasterboard, not cardboard.

There are different grades of marine ply.,  very likely the expensive stuff is waterproof.

Edited April 14, 2019 by LadyG

[LadyG]

20 hours ago, Chris Williams said:

My bridging pontoon which became the hull of my first boat was made of plywood.  It was thirty years old when I bought it and I had it for another five years.  Originally it was painted in Army green paint.  I stripped that and applied Bitumen.  No trouble with delamination, rot or anything else.

Does modern plywood not last as well as that produced during the war? 

Does anything?

...............................[rhetorical  Q by the way, Athy ]

Edited April 14, 2019 by LadyG

[starman]

50 minutes ago, LadyG said:

I had chipboard kitchen cabinets once [unknowingly], they delaminated. My bath panel was mdf, it soaks up water then disintegrates. 

I would never compromise on  quality products in any work. The labour costs are well outwith the cost of materials.  I'd rather use a paper based product than plasterboard in a boat! Not plasterboard, not cardboard.

To be fair, virtually all kitchen cabinet carcasses are made from the cheapest chipboard and sit in some dark damp areas like behind the sink so they can and do rot. As does standard (brown) mdf. Water resistant (green) mdf is much more durable. 

But even the finest quality tree wood will rot in damp conditions as anyone with an old wooden floor in their house will likely testify. 

[LadyG]

6 minutes ago, starman said:

To be fair, virtually all kitchen cabinet carcasses are made from the cheapest chipboard and sit in some dark damp areas like behind the sink so they can and do rot. As does standard (brown) mdf. Water resistant (green) mdf is much more durable. 

But even the finest quality tree wood will rot in damp conditions as anyone with an old wooden floor in their house will likely testify. 

It was the cabinet doors that de laminated, in my innocence I assumed they were wood, but they were wallpaper on top of chipboard. The original cabinets fitted in 1965 did not de-laminated, the doors fell off their hinges and fell to pieces , after only forty years!

Edited April 14, 2019 by LadyG

[Bee]

Its the damp innit. Anything that is dry will last ok but as soon as the edges get damp its in trouble. Even condensation is only a big problem when it runs down cold steel or glass and pools somewhere where it gets wicked up by some sort of particle board/ply/solid wood. As far as the problems of replacing soggy bathroom flooring is concerned, or soggy flooring anywhere in fact, it really should be best practice that flooring does not run under bulkheads or walls. It should be possible to lift sections to get access to underneath. I've never actually done it that way, its hellish time consuming or expensive but I think I would if I did another boat.

[starman]

32 minutes ago, LadyG said:

It was the cabinet doors that de laminated, in my innocence I assumed they were wood, but they were wallpaper on top of chipboard. The original cabinets fitted in 1965 did not de-laminated, the doors fell off their hinges and fell to pieces , after only forty years!

???

[Chris Williams]

3 hours ago, Bee said:

it really should be best practice that flooring does not run under bulkheads or walls. It should be possible to lift sections to get access to underneath.

My house (1960s) has flooring made of shuttering panels. The first floor was then built on top of the panels.  Brilliant.  Pad saw job to do anything.  The whole thing came in sections on the back of a lorry.  The sections were bolted together - I have found several loose bolts.