Kiln dried vs Air dried oak

[tren]

Hi All,

Am about to buy some planned timber to make casement windows and external doors for a coastal barn in West Cornwall where the level of humidity is quiet high.

I have had a quote from 3 different suppliers but one question I have is if I should go with Air dried vs Kiln dried. Prices seem to vary greatly between the two.

I will be using 57x57 and 57x95 timbers for the windows and doors construction. And I will be building them pretty soon after delivery.

One supplier who is significantly more expensive is recommending Air dried but it seems that in fact both could be used.

What would be best to use?

Thanks

 

[niall Y]

I have always found air dried to be a lot nicer to work with. I once constructed a balcony for a farm house, , using their own home grown oak. It had been dimensioned and air dried for several years in a barn.. It was a joy to work with. And, I have always used it for outside work such as benches and gates.

Of course the thicker it is the more years it has to be kept before sale which can crank up the price. When selling wood, this is not always a convenient strategy if you need a quick return on your investment.

I used to use kiln-dried oak strips that were the off-cuts from sawn 1" boards, as bean sticks. And, I was always surprised at how quickly they rotted at ground level - often in the first year. I believe this used to be called " the grave yard test" That kiln dried oak could perform so badly was a bit disconcerting.

 

[Fitzroy]

Wood tries to equalize moisture content with it's surroundings.

• Air dried timber will be equalized with ambient conditions and I would expect to dry somewhat further once made into windows, due to one face contacting internal humidity conditions. Wood will shrink, and expose gaps.
• Kiln dried timber will be equalized with kilned conditions and I would expect to gain moisture somewhat once made into windows, due to one face contacting external humidity conditions. Wood will expand, and no gaps form.

I use quite a bit of air dried timber (been stacked in my yard for years), and I've found I need to bring it into the workshop for a good period to equalize before I think about making anything from it that goes in the house.

F.

 

[tren]

Thanks both, so if I understand well for windows and doors Air dried wood has an advantage.

My dilemma is that I was quoted £6,000 for the air dried while I can get kiln dried for £4,800. Is it worth paying that much more?

 

[RobNichols]

How quickly do you need to use wood? If you have a few months before it is needed, you could buy kiln dried and then leave it to acclimatize to your ambient environment before you use it.

 

[niall Y]

If the oak is going to be left to silver on the outside and age naturally then air dried would be my preference. If the windows and doors just need to be oak, because that is what the customer has specified and will have a finish applied which will be maintained on an ongoing basis. then, kiln dried should be okay.
You could leave it up to the customer to decide, ultimately, it is they who will be paying the extra cost. I'm sure that, nine times out of ten, they will go for the cheaper option

 

[tren]

If the oak is going to be left to silver on the outside and age naturally then air dried would be my preference. If the windows and doors just need to be oak, because that is what the customer has specified and will have a finish applied which will be maintained on an ongoing basis. then, kiln dried should be okay.
You could leave it up to the customer to decide, ultimately, it is they who will be paying the extra cost. I'm sure that, nine times out of ten, they will go for the cheaper option

The customer is myself in this case
Just been told by my neighbour use kiln dried 10 years ago for his windows that have been left to weathered without any issue so perhaps I can save myself a significant amount of money here.

 

[niall Y]

The customer is myself in this case
Just been told by my neighbour use kiln dried 10 years ago for his windows that have been left to weathered without any issue so perhaps I can save myself a significant amount of money here.

There you go - I would make the same decision in your position. £1000.+ is not an insubstantial amount of money to save if you are the customer.

 

[Cabinetman]

I was building a bed to a clients design a few years ago, it called fo 4” square legs, The timber yard I use whilst excellent only had Oak that was air dried over 3 inch thick, they told me that the moisture conrent would be around 20% which it nearly was. I left a piece of it on the bed of my TS and next morning it was red rust!
As @Fitzroy so well explained it may be better to use timber that will close joints up rather than the opposite so kiln dried wins.
Ian
Ps have sent you a PM, click on the envelope on the top blue bar. Ian

 

[tren]

I was building a bed to a clients design a few years ago, it called fo 4” square legs, The timber yard I use whilst excellent only had Oak that was air dried over 3 inch thick, they told me that the moisture conrent would be around 20% which it nearly was. I left a piece of it on the bed of my TS and next morning it was red rust!
As @Fitzroy so well explained it may be better to use timber that will close joints up rather than the opposite so kiln dried wins.
Ian
Ps have sent you a PM, click on the envelope on the top blue bar. Ian

Thank you so much Ian. Rgds

 

[HOJ]

I only use KD Oak for joinery, windows and doors etc, and AD or green for outside construction jobs.

As in:


Also seems a bit odd that the AD Oak is dearer than KD!


You have outlined buying dimensioned stock (which seems very limited in the two stock size options you quoted) you will be paying a premium, plus you are not getting the benefit of keeping the offcuts/waste.

 

[johnnyb]

Oak often has 2 or 3 grades and prime is what's needed really. What grade is being offered is not mentioned. I wouldn't pay extra for air dried unless it was special in some way.

 

[Billy_wizz]

I have always found air dried to be a lot nicer to work with. I once constructed a balcony for a farm house, , using their own home grown oak. It had been dimensioned and air dried for several years in a barn.. It was a joy to work with. And, I have always used it for outside work such as benches and gates.

Of course the thicker it is the more years it has to be kept before sale which can crank up the price. When selling wood, this is not always a convenient strategy if you need a quick return on your investment.

I used to use kiln-dried oak strips that were the off-cuts from sawn 1" boards, as bean sticks. And, I was always surprised at how quickly they rotted at ground level - often in the first year. I believe this used to be called " the grave yard test" That kiln dried oak could perform so badly was a bit disconcerting.

If there the off cuts wouldn't they be mostly sapwood rather than heart wood? I believe there is a significant difference between the two on most oaks

 

[tren]

I only use KD Oak for joinery, windows and doors etc, and AD or green for outside construction jobs.

As in:
View attachment 176019 View attachment 176020

Also seems a bit odd that the AD Oak is dearer than KD!


You have outlined buying dimensioned stock (which seems very limited in the two stock size options you quoted) you will be paying a premium, plus you are not getting the benefit of keeping the offcuts/waste.

Thanks for confirming. Kiln dried it is.

Just to clarify, only one supplier quoted me air dried and their quote was £1k more than another competitor kiln dried.

Fair point with regards to sizes, I am only a starting hobbyist with limited amount of space and machinery. They will actually be my first windows and doors (which need to be fitted asap due to planning) so I kind of need to cut corners even though I understand it's not the most cost efficient way of doing it.

 

[Ollie78]

I have used both my conclusion is that the air dried is less brittle and a bit nicer to work with.
The trouble is half of your window or door is inside and half outside. For exterior stuff like gates air dried is recommended as it should have a bit more moisture left in it so when it gets wet should expand less. But in your case only half of it is outside! Can't win.
Anyway, I recently did some gates and a big door with air dried and it seems fine.

I am a bit surprised at your pricing. I would certainly expect the air dried to be cheaper for the same volume. Are you comparing the same grades directly or is the air dried prime and the kiln dried a lower grade?

On an order that size you could get it waney edged and throw in a planer/ thicknesser for the same money. Buying planed always seems mad expensive to me.

Ollie

 

[niall Y]

If there the off cuts wouldn't they be mostly sapwood rather than heart wood? I believe there is a significant difference between the two on most oaks

There is indeed a difference in performance with the sap wood but it was the heartwood that was rotting. At that time I was using square sawn stock with little or no sapwood, so the results surprised me.

 

[johnnyb]

Air dried has rather more subtle advantages for hand tool guys as the lignin doesn't set making it much more buttery and forgiving. Air dried will still steam bend whereas kiln dried is almost impossible. This suggests a more fundamental change than simply less moisture. Prime grade Air dried slowly dehumidifier to the perfect moisture content over a longer time would be the very best. American exported woods are kilned really dry and generally unsuitable but white oak is considered an exterior wood over there

 

[HOJ]

They will actually be my first windows and doors (which need to be fitted asap due to planning) so I kind of need to cut corners even though I understand it's not the most cost efficient way of doing it.

Why have you got to rush to make them, planning normally gives you 3 years to start, and within the planning application did you not have to submit design details/specs to follow, not trying to be negative but you may well end up wasting money if you don't have a detailed construction spec.

 

[tren]

Why have you got to rush to make them, planning normally gives you 3 years to start, and within the planning application did you not have to submit design details/specs to follow, not trying to be negative but you may well end up wasting money if you don't have a detailed construction spec.

We have a 6 months deadline (to complete a barn conversion) due to a Bats licence imposed by Natural England. And because none of it was clearly mentioned us at the time we are pretty half way through that deadline already. So I have 3-4months to get my windows done.
Having said that I have clear plans for the windows and the machinery/tools. So I just need to get the wood and crack on with it.