Wood shrinkage problem

[fobos8]

Hi everyone

Last November I built a set of gates for our drive. They're made from Scandanavian Redwood (softwood) which I bought from a farm up the road.

Each gates is constructed with a frame which is filled in with a row of vertical "slats". The slats were glued together to form a kind of closed panel. I finished the gates with some oak effect Cuprinol external wood paint.

In the new year when I fitted them they looked wonderful. However as the heat has risen throughout the year the slatted panels have shrunk big time. You can now see between most of them, and between some I can even fit my little finger!

I think that all of this is down to the wood shrinking but I just need to know what I should do next time I make some gates.

My gut feeling is that I should buy the timer elsewhere. If so how can I be sure the same thing won't happen again?

Should I be sealing the gates with something better than paint so that they can't expand or contract depending on the weather?

Can anyone offer some advise on this subject?

Many thanks, Andrew

 

[tim]

Its probably not the timber but more likely the design.

Timber only expands across the grain so edge gluing all the slats is asking for trouble. Paint also does not necessarily seal the timber.

Were the slats butt edged or did you tongue and groove them?

Unless you incorporate expansion into your design then these problems will reoccur.

Cheers

Tim

 

[George_N]

I don't think Cuprinol or any other wood treatment will stop wood moving with changes in humidity. Maybe the timber you used hadn't been dried properly, but even so, outdoor timber will still expand and contract with changes in humidity, some timbers more than others.

cheers

George

 

[RogerS]

Hi Andrew

I built a garden gate last year. The thread is here

The panelling was T&G but I nailed it as per the thread. It was then painted with the usual primer, undercoat using Farrow & Ball paints. So far there has been zero movement in any direction and so I'm quite chuffed. Possibly your wood wasn't as dry as mine was?

Mind you, I don't really rate Cuprinol stuff preferring Sadolin or Sikkens.

 

[j]

Maybe you could design the gate with gaps between the slats, so not a solid panel.
If you want to cut down visibility, maybe go for a louvred panel effect.
might look a bit odd now that I think about it.

 

[SketchUp Guru]

It seems to me that trying to stop wood from moving with humidity changes is asking for trouble. Masking the changes with joinery makes more sense. Tongue and groove joints are a good option. You could also cut mating rebates along the edges so that the boards overlap. Bevel the edges at the seams and the gap won't be as noticeable.

 

[fobos8]

Hi guys

Thanks for your answers so far - they're great. I think I now realise why people use tongue and groove.... The vertical slats were not t&g - I simply edge butted and glued them against each other and then screwed every fifth one.

I think I'm gonna re-do the slats cos the hotter it gets the worse they look. I think I will use the suggested mating rebate and overlapping method.

Am I correct to assume that I SHOULDN'T glue the edge joints together?

What should I be doing differently when I finish them. I just put the paint staight on - no sealer. Should I 'seal' them with anything to control expansion/contraction?

Thanks again, Andrew

 

[George_N]

Am I correct to assume that I SHOULDN'T glue the edge joints together?

That is correct. Un-glued T&G joints allow the wood to move. Usually just one nail top and bottom of each board and into a cross- brace if your design has one.

cheers

George

 

[wrightclan]

That is correct. Un-glued T&G joints allow the wood to move. Usually just one nail top and bottom of each board and into a cross- brace if your design has one.

cheers

George

A further consideration in allowing the wood to move is to use screws with an elongated pilot hole where the boards are attached to the rails. Wood moves far less along the grain than across it, so when you attach several stiles at right angles to the top and bottom rail, that is a lot of movement across the width of the gate, whereas the rails will hardly move across that width. You could forget about the elongated hole in the centre stile, keeping the whole construction centred, but allowing movement on both sides.

Brad

 

[wrightclan]

After posting my last response, I went back and re-read the first post. Am I correct in understanding that that the frame captures the panel, like a frame and panel construction for interior cabinetry? If so, my previous comments are irrelevant. In fact, it should not be a problem gluing the tongue and grooved panel together, as long as the panel is allowed to float freely within the frame. In fact, I have a shed door which I have made in just that way, with no problems.

Brad

 

[fobos8]

Thanks for all your help everyone for the advise in constructing the gate 'panels'. I've got is sussed now.

I just redid them last night using rebated overlaps. I just need to sort out the finishing now to minimise any movement. Is there something I can coat them with to achieve this? Anyone know how boats hulls are treated to stop adjacent planks of timber from moving?

Cheers, Andrew

 

[Nick W]

You keep them in water!

Wooden boats are renowned for sinking as soon as you put them in water, but they become 'tight' in fairly short order. Just need to pump them out then.

 

[fobos8]

Do I just coat them with undercoat + paint or is there something else I should be using in addition to this?

Any takers??

 

[Paul Chapman]

Are you talking about conventional paint? If so, I wouldn't have thought this was the best treatment for exterior gates. I can envisage them peeling and you forever sanding them down and re-painting them. Why not a wood preservative like Sadolin Classic? Or if you must use paint, perhaps try a microporous one - I think Sadolin do it in black or white, but I've not tried it yet.

Paul

 

[RogerS]

Are you talking about conventional paint? If so, I wouldn't have thought this was the best treatment for exterior gates. I can envisage them peeling and you forever sanding them down and re-painting them. Why not a wood preservative like Sadolin Classic? Or if you must use paint, perhaps try a microporous one - I think Sadolin do it in black or white, but I've not tried it yet.

Paul

If that were the case, Paul, then we wouldn't paint our houses externally, would we? Modern paints, applied correctly and on a decent surface do last. I've been putting Sadolin on the oak surrounds to my workshop and the treatment only lasts a year before I need a recoat

 

[Paul Chapman]

If that were the case, Paul, then we wouldn't paint our houses externally, would we?

I've always wondered, Roger, how paint ever caught on as a treatment for exterior woodwork. I know manufacturers and decorators always say that if it's applied properly, etc, etc, it works but I think in most people's experience it doesn't. It can be quite successful if your house faces the right way and the painted surface is well protected from the weather, but in most cases I think it's a bit of a disaster. The problem is that it sits on top of the wood so will eventually break down, so you will spend the rest of your life burning, stripping or sanding it off.

For exterior gates, which will get a real bashing from the weather, my choice would be creosote or something like Sadolin which will sink into the wood and not sit on the surface

Paul