Oak shrinkage for outdoor use

[doobin]

Another shrinkage question for the pros. I want to end up with 30mmx150mm boards for replicating an oak garden gate that is full of woodworm for a customer (minus the woodworm obviously). What size should I cut at initially?

[topchippyles]

58 minutes ago, doobin said:

Another shrinkage question for the pros. I want to end up with 30mmx150mm boards for replicating an oak garden gate that is full of woodworm for a customer (minus the woodworm obviously). What size should I cut at initially?

38mm X 158/160mm pre planed will be fine 

Edited May 14, 2022 by topchippyles

[trigger_andy]

1 hour ago, doobin said:

Another shrinkage question for the pros. I want to end up with 30mmx150mm boards for replicating an oak garden gate that is full of woodworm for a customer (minus the woodworm obviously). What size should I cut at initially?

When are you going to build it? This year or next? 
 

Gonna plane the boards or keep them off the saw? 
 

Personally I’d build the gate green unless there’s some M&T involved. If you can build it green and plan on planing then just mill a few mm over on each side. 

 

Even if there is some T&G involved for an outside gate I’d still build it green. 

 

Edited May 14, 2022 by trigger_andy

[Mull]

Thickness cut will obviously shrink to a lesser degree than width cut considering it’s 5 times smaller, so will require less oversizing

[doobin]

No tongue and groove. I did wonder about just building it green- it’s copying a very basic design (gonna salvage the old ironmongery) 

[Mull]

What are your options? Building green and building seasoned? If that’s the case , why build green?

[Macpherson]

+ 1 for building green, I've got an oak gate that was built too tight [ not by me ] and the natural movement in it stresses it quite heavily throughout the changing seasons👍

[Mull]

+ 1 for building green, I've got an oak gate that was built too tight [ not by me ] and the natural movement in it stresses it quite heavily throughout the changing seasons[emoji106]

Ahh, right, I see your point, to a degree anyway! If you build it green it can’t get tight! But if you build it dry you don’t allow expansion?? Why not?

[Macpherson]

2 minutes ago, Mull said:

Ahh, right, I see your point, to a degree anyway! If you build it green it can’t get tight! But if you build it dry you don’t allow expansion?? Why not?

 

Aye, wasn't meaning to contradict you're post which popped up while I was typing. 

 

Years ago I thought I got a bargain when I bought a very posh Oak garden gate that had been built with similar carpentry methods that would normally be used for a door and that's what I used it for, an extra wide shed door.... it was going cheap from a bespoke manufacturer as had been built the wrong size for their client.

 

Mortise and tenon framework with inset t&g facia and even though I've treated it heavily with solvent based products as it bears the brunt of the weather it seasonally moves considerably more than I'd have expected, that's why I think it might  be better to assemble Oak joinery that's going to be exposed to the weather perhaps not totally green but certainly not bone dry, maybe somewhere in the middle.

 

Woodworking constantly gives me in equal quantities enjoyment and frustration 🙃 cheers.

[ucoulddoit]

Not relevant to the original question, but regarding green/wet versus dry timber, pretty sure there should be less in service movement in timbers that absorb moisture compared to wetter wood that has dried down to the same relative humidity. The equilibrium moisture content of wood which has been kiln dried to say 12%, then left outside to acclimatise to the ambient relative humidity, will be lower than wet wood left outside to air dry and acclimatise down to the same ambient relative humidity. No matter how long the two pieces are left outside. 
 

Probably not relevant for a ‘rustic gate’ but could be for an external door and more so in furniture making. I aim to dry timbers for furniture making to a moisture content which corresponds to less than the expected ambient indoor relative humidity. Then store the wood for a while to acclimatise to a slightly higher relative humidity which in theory makes the wood a bit more ‘stable’ and the subsequent furniture better able to tolerate variation of relative humidity indoors at different times of the year.

 

Andrew