Garden Bench Moisture Content

[John15]

I am currently making a 5' long garden seat in Oak.
My question is: What moisture content should I try to achieve while making it, with consideration to the very dry and very wet weather we get here in The UK?
The timber is stored in my wooden work-shed and currently has an MC of 11 to 14%. So far I have cut the components to size but am holding back on cutting the joints, all M & T, until I'm confident about what the optimum MC should be.
I've researched past posts and found one from 2004 by Alf who recommends 16% for outside furniture. Does this sound about right?
I have a greenhouse where I can store the parts - maybe this would bump it up a bit.
Cheers,
John

 

[Peter Sefton]

I would say 16% and above for outside furniture if you are using air dried timber you should be about right. You could leave your timber outside under cover for a couple of weeks if you think it is to dry.
Peter

 

[John15]

Hi Peter,

Thanks for that. Do you know what happens at the joints when the weather changes between long periods of wet to long periods of hot and dry conditions? You see benches left out throughout the year in public parks and gardens with no apparent movement or damage around the joints, yet for indoor furniture the MC is more critical to avoid any shrinkage or expansion.

Cheers,
John

 

[Peter Sefton]

Hi John
I am no expert on garden furniture but I would say that the sections of timber (bench or table slats) would be 60 to 70mm wide and they all move individually. Interior furniture would have solid wide table tops and therefore movement over a mass of 600 or 900mm wide which we control with good construction techniques to allow for movement.
The garden bench joints should be glued with an exterior glue (Titebond 111) they could have shoulders on all four sides of the tenon to help cover up any shrinkage, you may also wish to pin the tenons with a Oak dowel through the glued up joint.
You may get some better advice from one of the forum members who works more on joinery and exterior woodwork as water ingress does cause other issues.
Cheers Peter

 

[John15]

Hi Peter,

Yes, I think you're right. The seat is made up of around 30 pieces and all are small in cross-section so I guess any expansion or contraction due to moisture changes would be small.

I've moved the prepared parts into my greenhouse to try to get the MC to 16% before cutting the joints.

Thanks again for your advice.

John

 

[Peter Sefton]

I hope it all goes well and we get a summer this year :!:
Peter