Marine and WBP Plywood Application

WTF, does the TLA, WBP stand for:

Plywood isn't a 'good' material for a door. I assume here we are talking about a swinging man-door, as opposed to a cabinet, cupboard...

Is plywood 'good enough' for your application? That's up to you. If you varnish or paint the living daylights out of it, it may well perform fine. Finding door hardware that will work will probably become another issue.

The inherent dimensional instability of wood is the reason. If you look at a manufactured wood door, you will see that effort has been made to actually reduce the amount of wood (lumber or veneer) in the door. The more wood in a door, the more likely it is to eventually warp - twist - bow.

[edit] WBP plywood (water boiled proofing) means exterior grade plywood.

Plywood can make excellent doors.

There are all sorts of plywoods.

Unless you make a hollow core door Two thin pieces of wood over a frame,

It will warp and be very heavy.

Marine plywood may be WBP plywood as WBP is a test for delamination of the sheets by boiling. So you need to look at what the binder is holding the sheets together. Some of the binders hold out longer in the test then others.

Cost depends on a lot of factors. One would be what binder was used.

Are you trying to make your own door?

In our house the interior doors are all prefabricated pre-hung hollow core doors.

They have stood up well in the kitchen and bathrooms for over twenty years.

Exterior doors are by code either solid core wood doors, or steel clad, wood frame, foam filled. For longevity the steel clad doors tend to stay straight, but are more prone to dents, and eventual rust if you don't keep them painted. The steel clad doors tend to be more burglar resistant. The solid wood doors are esthetically more pleasing, but definitely take more upkeep.

If the door is between apartments that must have a fire rating, then they are solid wood core or steel that has a fire rating.

The solid wood core doors are heavy. They can have a "particle" wood core, or have a lumber core. The particle wood cores tend to swell badly if soaked in water.

(solid wood core doors make good bench tops :)

If you are talking about doors on a boat - then perhaps a nice mahogany panel door would be appealing.

This is beginning to remind me of a joke about a fellow with a peculiarly acute olfactory sense. Something about a tuna boat...

want a screen door for your submarine?

....and a Brothel?

Never seen one made of ply...

He was challenged to identify different species of wood, correct?

Cover up WBP on both sides and on top and bottom with laminate (Formica) and seal it. Such plywood will be good enough for bathrooms also. This is how I have done with my home inner doors. They have lasted long.

http://pdf.archiexpo.com/pdf/formica/formica-collection-doors/4204-205965.html

The doors to our bathrooms are standard hollow-core plywood veneer construction, with each surface plywood about 2.5mm thick, and the visible layer of possibly birch or maple, with probably two coats of varnish. The hinges have rusted, and every other bathroom surface (except the mirror) has been recovered at least once, but the doors still look like new after 53 years.

We don't live in an excessively humid climate, but it's not desert, either.

It depends upon what the local Building Regulations say. They can't be seen from here.

The type of door hasn't been stated so:

PLYWOOD- Interior soft wood uses Urea-Formaldehyde glue. Less resistant to water. Has voids in interior layers.

Exterior soft wood uses Phenol-Formaldehyde. Water resistant but not waterproof. Small voids in interior layers.

Marine Plywood has no voids in interior layers. Resorcinol glue which is waterproof. Also about 3-4 times the cost of exterior grade plywood. Marine plywood is also used for other applications besides boats. (You will know how waterproof it is after you get some on your clothes instead of the rag)

Use whatever meets your requirement. Strongly do not recommend plywood for flush (flat surfaced) doors. It is much more expensive and the weight of a pre-hung door 1-3/8" thick, normal thickness, would be about 130 lbs.

A painted hollow core door would be sufficient for a kitchen or toilet area. They are made by laminating wood and cardboard between two sheets of thin plywood, veneer, Masonite, pressed Masonite (decorative or grained) and other materials. is placed face down on a table. The wooden core perimeter pieces and lock block are then glued on each of their faces with casein glue (a milk derivative) between two rubber gluing rollers. These are placed in their appropriate places and a honeycomb of corrugated cardboard is glued on its edges and expanded in the center voids. Another face panel face up is placed on the door pieces. This is then heated to cure the glue.

For solid core doors, MDF, particle board, special fire proofing compounds and other materials can be put in the centers. Painting the door with a good grade interior or exterior latex or oil based paint will seal enough for bathrooms and kitchens.

Interior wooden doors, such as the 6 panel solid door are fabricated and glued from various types and grades of wood. Most types of solid wooden doors are available in hollow core door types.

I would not go with a plywood door because of cost and weight. Hollow core or solid core would be my choice because of lower prices, almost identical appearances and better resistance to warping, etc.

Would never use marine plywood for most anything but boats. Too expensive and little added benefit for other than boats.

Hollow core doors make good lightweight work benches such as for electronics or lightweight assembly. Solid core doors make good benches for hammering and greater weight capacity. Whatever you use put a replaceable panel of Formica on it to prevent surface damages.

Good Luck, Old Salt

I made double plywood doors, 4' X 8', for the exterior doors of my workshop 20 years ago. They are still stable and functional. I mounted the 1/2" fir plywood on 2X4 frames with a diagonal brace and sealed the doors with siding sealer. I live in south Louisiana: hot and humid!

Good luck.

Don

The right plywood properly installed can be just the ticket and provide a lifetime of service.

Your frame brace however is redundant once the plywood is fixed to it. It can stay in place I suppose.

Good info. You really know what you are doing!! (more than some here!!)

I am not an expert on wood, though I have built a few things in my life too (that are still standing also after many years!) and what you wrote makes good sense.

It appears that some here simply do not know how to tell certain types of boards from each other and which are good longterm items to use for outside projects and which are not for instance!!