Gluing plywood to plywood for doll's house floor

Question

I am making a small doll's house for my daughter. This is my first project; I am a total beginner at woodworking, basically what I know is remembered from watching my dad 30 years ago :)

It's going pretty well, I have cut the panels, and even managed to get some perfect rectangles cut for windows; however when cutting them I noticed that of course, the plywood delaminates very easily - in fact much more easily that I expected.

A front view of what I was planning to do:

So I plan to make the base and main ceiling out of pine so I could screw into it for strength, however the floor was just going to be plywood glued, along with some mouldings as batons to increase the surface area along the side.

Will this design be strong enough for the interior floor just with the glue? I know that the glue is stronger than the wood; my concern is that the top layer of plywood and glue will peel off and the floor will collapse if she bangs around too much (she's two and a half).

(There will be a back as well of course.)

Matt mentioned dimensions may be important:

It will be ~22cm x 34cm x 22cm (w x h x d)

The plywood is 8mm thick; the pine is 15mm.

The plywood is basically offcuts from my father in law, so is in "been knocking around the workshop" condition. Clean but a bit flaky.

The plywood has a paper thin veneer on one side in a reddish looking wood. I should have mentioned this actually, although I can just use the other side. I assume this was done for appearance - it is literally paper thin and flakes as soon as you bring a tool into the same room. I presume I should avoid gluing to this side altogether?

Answer 1

This would very much depend on the quality of your plywood which sounds questionable. You also don't mention the thickness which would play a role here as well. The overall dimensions of the project are not shown either. This is a dollhouse after all so I can't imagine its size would be a huge factor.

For screwing onto the base: That should be fine. If you wanted to make it stronger gluing it as well would help as well as make sure you screw into face grain and not end grain.

For the middle panel as long as you make a support for the plywood to rest on I imagine it would be fine. However you could consider making a dado (slot) for the floor to slide into.

Looking at designs online I see your ideas in play. The picture below has at least the back is for sure plywood and you can see glue on the joint for the roof in the upper right. Notice the partitions on the floors that add strength in the middle of the floors. Looking at the cut windows we can see that the whole design is just plywood and it is not a stretch to assume it is just glue holding the thing together.

Answer 2

I know that the glue is stronger than the wood;

Just to clarify something on this point, while this is widely said it's a little misleading. A well-made glue joint is stronger than the wood itself, but not actually the glue itself.

It's important to make the distinction because even unconsciously believing the glue is inherently strong can lead to an "it'll do" attitude to creating tight joints, which will most definitely have an impact on strength.

Note that this refers to conventional wood glues (PVA type), as well as polyurethane adhesives. Epoxies are different, and can give strong joints where the fit is loose because they have good gap-filling properties (especially if filled slightly).

the floor was just going to be plywood glued, along with some mouldings as batons to increase the surface area along the side.

Will this design be strong enough for the interior floor just with the glue?

Yes it should be. Even thought this is not a critical structure in terms of having to take weight I wouldn't want to trust a glued butt joint for the plywood shelf, however, glueing in the proposed mouldings underneath will add a great deal of strength.

The plywood has a paper thin veneer on one side in a reddish looking wood. ... I presume I should avoid gluing to this side altogether?

I refer to this in another Answer, and yes I think ideally you wouldn't want to glue to this. It's not just that it's very thin, it seems far too friable to trust for any important bond since you can often flake it from the next ply using only your fingernails.

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Re. the dados highlighted by Matt already, these are called housing joints in the UK and I think other parts of the world that don't use American English so you might want to add that to your list of things to Google for to widen the scope of information you can find.

Answer 3

There's an indirect question in here about the quality of plywood that I think is worth discussing. Plywood comes in all types and quality levels, both from a finish perspective as well as overall strength.

Most plywood, especially what you would find at a local home improvement store is intended for construction. Frequently this material contains voids at certain points throughout the layers. Because the material is not visible, the exposed layers aren't chosen for cosmetic properties. Quality varies by price and the cheaper stuff is used for things like temporary fences or covering a broken window. Higher quality material would be used for things like sub-floors or sheathing.

Baltic birch is one specific type of plywood that is frequently used in woodworking. This product should not contain any voids between layers so it is a much more solid product overall. It also takes well to rounded corners and chamfers. Usually at least one veneer face is suitable for finishing, and the higher end product (most expensive) will have high quality veneers on both sides. You should not have problems with thin layers sepearting when using Baltic birch.

Definitely make sure that you are using the right product for the job.