Plywood sheets (flat!)

[ClockPie]

Hi

My experience of Buildbase/B&Q type plywood is that its pretty naff and not as flat as you want. I have bought expensive lightweight ply (for campervan build, from campervan parts supplier) - and that was dead flat and light, but not available locally

Is there anything inbetween from normal type shops?

I'm considering using the ply in 500x2000 sections for fake wall (pull-out wall drawers) so it needs to be flat - and will be emulsioned to match wall. It would be fixed to (say) 420x1600 18mm thick good quality MFC (part of the shelves I'll build), glued n screwed, so the main part of it will be unable to warp. The edges will probably have 21x38 rear PSE battons glued on anyway to give strength and a thicker edge

So question on this thread is which is the best ply to get and where from? (12-15mm I guess?) And if the ply is glued/screwed to MFC over 80% of its surface area, is that enough to stop any future warping esp at the edges?

 

[pete50]

It's a pity nobody answered this thread. So far all the plywood that I have found, including so called marine play, is warped, has gaps in the laminate, has corners knocked off and has great clodhopper boot marks over it. It is absolute rubbish. The Chinese stuff is even worse.

 

[Deleted member 174758]

My experience of Buildbase/B&Q type plywood is that its pretty naff and not as flat as you want. I have bought expensive lightweight ply (for campervan build, from campervan parts supplier) - and that was dead flat and light, but not available locally

Is there anything inbetween from normal type shops

You've answered your own question, in a way. Don't buy plywood from the DIY warehouses - it is universally carp and extremely expensive to boot. The lightweight stuff you are referring to is probably Italian poplar plywood, a speciality of the caravan and coach building trades where weight ios a significant factor. In your place I'd start by ringing round the local plywood merchants (note - NOT timber yards but specialised suppliers) who will probably be cheaper than a campervan parts supplier if you can find one who will supply. It might also be worth ringing round anyone locally who does old-fashioned coach building or vehicle restoration (particularly on coaches, motor homes, etc) to see if you can buy a couple of sheets from them. Within 30 miles of us I happen to know that we have at least two firms building ambulance bodies, a horse box builder and at least four firms who refurbish/build/modify caravans and mobile homes. I seem to recall that when I needed some of this lightweight poplar ply about 15 years back that it came from a specialist plywood imported in the Hull area (a lot of the caravan trade is based in that part of the world).

The next sort of firm to approach is going to be a sheet material specialist such as Lawcris in Leeds, Silverman (London and nationwide), Bensons in Darwen, etc. They should be able to supply a good quality WBP plywood to an appropriate standard (i.e. NOT Chinese) but the issue is that it comes in 8 x 4ft (2440 x 1220) sheets as a rule and a lot of firms don't have breaking down facilities (although Lawcris and Bensons both do if you are in this part of the world) and they probably won't deliver a single sheet, or to a domestic address (well, 24 ton wagons don't fit well on housing estate roads, do they?) so you'll need to bear that in mind and maybe buy or hire a roof rack.

I'm considering using the ply in 500x2000 sections for fake wall (pull-out wall drawers) so it needs to be flat - and will be emulsioned to match wall.

I think that you'll need your own saw and guide to break the stuff down. And if you pump loads of water into it by slapping on emulsion it isn't going to stay flat for long. Oil-based paints are far better in that respect, or possibly a matched 2-pack lacquer from a firm such as H Marcel Guest (HMG) or Morrells (both in Manchester but with national networks).

It would be fixed to (say) 420x1600 18mm thick good quality MFC (part of the shelves I'll build), glued n screwed, so the main part of it will be unable to warp.

MFC, good quality? I hope that you can find a supplier. Probably the best quality MFC you'll find is Egger, but it is really heavy and you'll struggle to find much other than 15 and 18mm (8mm and 12mm is available from the better places). Personally I'd consider making the lot from 12mm poplar plywood and laminating (both sides) as required. If you need solid wood for framing or lipping then go for poplar (sometimes sold as tulip wood)and get the timber merchant to machine it to dimension for you - it is commonly available from proper timber merchants, light, strong and relatively cheap

 

[ClockPie]

Good info there, thanks.
We already have the MFC - we had a kitchen from diy-kitchens last year, and they also sell cut to sized, edged, strong, 18mm thick, and very good MFC (really meant for kitchen bits). So we just ordered all the correct sizes for our shelves and stored it to this year. It really is strong stuff so sure it'll be fine.

Hadn't considered the effect of the water in the emulsion contributing to warping. It needs tp be emulsion to match what we want, so I may have to take that hit. Would painting encourage bowing outward (edges towards the painted side) or inward (edges away from painted side). Would a coat of oil-based primer (eg Zinser BIN) prevent the water going into the ply? (Had v good results emulsioning over zinser BIN on a stained/mould area in the house)

I'll google plywood merchants - I never knew such companies existed (!) and worst case I'll go back to the campervan supplier I used. I can cut the sheets in half and carry OK.

Yet another simple "idea" that isn't lol

 

[ClockPie]

FFS.

After talking to the wife about the possible emulsion issue, then looking at other similar project photos online, she is now happy with gloss finish lol! Which is what was suggested at the start but she said no.

Which means we can do it differently and simpler than the hidden wall idea.

Round and round and round we go!

 

[JohnD]

I think an oil-based wood primer (I like Aluminium wood primer) especially on the edges is a good starting point. Then you can use water-based undercoats and topcoats. With a gappy ply, I bought some (non-medical) syringes and injected weatherproof wood glue into any holes before sanding and varnishing. Mine was for a bathroom so I think I needed to be more particular about damp penetration.

 

[Deleted member 174758]

Would painting encourage bowing outward (edges towards the painted side) or inward (edges away from painted side). Would a coat of oil-based primer (eg Zinser BIN) prevent the water going into the ply?

As suggested by the previous poster it is possible to seal the plywood first - the main thing I would emphasisi is the need to seal ALL the surfaces - seal just the outside and the plywood will bow in the middle, etc.......