Wood movement

[ScottGoddard]

I understand the basics of wood movement. However, after watching several youtube builds (some of the better makers as well) i have notice that wood movement is only considered on the tops of tables etc. When makers have built and used solid wood (not ply etc) for the backs/sides (i have mainly seen dove tails / floating tenons for joinery) they dont worry about movement - WHY is this?

 

[Peter Sefton]

If it's a dovetailed carcass and designed correctly all the components should move in harmony with each other. If it's a wide solid cabinet back and no movement has been allowed for then they possibly don't know what they are doing.

I covered timber movement in the Timber Selection DVD (sorry not free). This covers a lot of areas but not every construction possible. I am afraid it's an area of woodworking often overlooked or not understood but very important to furniture makers.

Cheers Peter

 

[MikeG.]

.........i have notice that wood movement is only considered on the tops of tables etc...........

That simply isn't true. It will be considered everywhere where cross grain meets long grain.

 

[Mr T]

.........i have notice that wood movement is only considered on the tops of tables etc...........

That simply isn't true. It will be considered everywhere where cross grain meets long grain.

It could be true Mike if the maker did not know what they were doing. It would be interesting if the OP could be more specific

Chris

 

[ScottGoddard]

this is probably my lack of understanding and a big assumption of my part....

for example in this video (https://www.youtube.com/watch?v=skWizR_-LSs) i cant see how he is allowing for the wood movement. Another example would be kingpost timber video (https://www.youtube.com/watch?v=JfxBDdszXeI). It is probably my complete lack of understanding

 

[woodbrains]

Hello,

I watched the first video. You'll have to elaborate on the bits you don't understand or I'll just be guessing. It all looks fine TBH, though not everything was shown in the video, and these are likely the bits that explain more.

I'll take a punt at 2 things being problematic if the whole story is not being told, and what I think is going on.

The crown moulding on the top case is going across grain to the carcase sides. If it was fixed it would be a problem but it is not shown how it is attached in the video. I'll bet a pound to a pinch, it is not glued, but slid onto dovetailed keys, so the moulding will effectively slide as the carcase sides expand and contract seasonally.

The bottom case doesn't have this problem as the case side is orientated with the long grain running front to back. The moulding can be glued here. The seasonal movement will be vertically in the lower case. The only problem here is the fit of the drawers, but that is accounted for by leaving the drawer sides with a fair bit of room for the carcase to move vertically around them. The drawer fronts are rebated all round, essentially an overlay, to hide the larger than (aesthetically) optimal gaps at the top. There could be a problem where the lower case sides meet the stiles, but again there is no detail as to how they are fixed. Could be sliding dovetails. However, the time when this piece was originally made, it might just have been nailed. There is a bit of movement tolerance with nailing, especially with walnut which has a very small movement in service. You will probably have noticed how many antiques have splits in the sides, though! It may well be that the makers just followed the old ways and it will just crack. Believe it or not, I have heard it said that that is the expectation and it is fine, it is a verbatim copy because the client wanted it to be so.

I didn't look at the second video, but saw the first 20 seconds. As far as I saw, the carcase looks fine.

What are you having trouble with?

Mike.

 

[Peter Sefton]

Just had a quick scan look over the videos, as mentioned in the first video their could be an issue with the cornice but this may have been allowed for in the construction (glued at the mitres slot fixed at the back) The lower cabinet side could be an issue but this is a reproduction piece and follows to traditional construction methods. There is a fair chance the sides might split a little.

In the second video he seems to have considered timber movement, the three elements that I looked at were.

1 Sitting the carcass on the plinth, the plinth was rebated on three sides allowing for movement at the back, thats correct.

2 The back was made of narrow strips each fixed independently to allow for movement.

3 The drawer bottoms are plywood so not a problem.

I would say are they are good makers who both understand what they are doing.

Cheers Peter

 

[ScottGoddard]

Many thanks for all your help. I now realise my understanding of wood movement in relation to building needs a great deal more understanding. Thanks for all taking the time to reply. More reading is needed for the next projects......Bathroom cabinet and hall table.

Just been doing so reading up on wood movement. One of my builds is going to be a hall table, clear cross and long grain will meet...I was planning a standard tenon joint and glueing. However, some of the stuff i have read suggest not to glue for movement, is this correct? Give the short cross section would it move much?

 

[Mr T]

I had a quick look at the second vid and agree with Peter. The case is free floating on the plinth, the back is slatted so movement is accomodated between slats, the dust board framers are probably fixed at the front but free at the back and I thhink there is a slight gap between the back of the frames and the back.

You ask about gluing up your mortice and tenon, how wide is the joint?

Chris

 

[ScottGoddard]

Chris thanks for the informantion. Not fixed at present, the rails would probably be about 15 cm, so the joint would be about 12 cm (3 cm left at the top of the leg).

 

[Mr T]

I think you would be OK gluing that. If you have a 10mm shoulder at the other end it would be about 110mm wide. There may be a little shrinkage possible causing a slight step between rail and leg but this will be negligible.

Chris