Green oak question

[electricianid]

I will soon be replacing my soffits and eaves with some oak which I intend to treat with two or three coats of linseed oil. A local sawmill who I approached for a quote has suggested that I use fresh sawn oak as opposed to air or kiln dried (12%) as it's for an outside job, but wouldn't this result in cupping, warping etc?
Should I buy the fresh sawn or go for the 12% stuff? To make matters worse I have also noticed an ebay company selling 30% part dried oak.
p.s. The profile I have been getting quotes for is 150 x 20 mm

 

[middi]

If the sections of oak you are intending to use are only 150x20mm it is better to use well seasoned or kiln dried, there will be less distortion and uneven lines as opposed to green oak " small planks". The kiln dried or seasoned cost for those dimensions is not terribly expensive as compared to 50, 75 or 100 mm thick planks.

There is no reason why you cannot use the cheaper green oak, once screwed to the anchoring points it should remain resonably straight albeit a little bit more shrinking will take place.

 

[biffvernon]

Seems a bit silly to kiln dry to 12% and then hang it up in the rain. I'd think the compromise of 'air dried', ie it's been left in stick for a couple of years might be better than either green or kilned. Moisture content might be between 15 and 20 %.

 

[electricianid]

There is no reason why you cannot use the cheaper green oak, once screwed to the anchoring points it should remain resonably straight albeit a little bit more shrinking will take place.

This sounds like a good comprimise, still a bit worried over how much shrinking to expect.

Regarding the respective costs, I have been quoted £60 for the green oak and up to £650 for the kiln dried!

Seems a bit silly to kiln dry to 12% and then hang it up in the rain.

Put that way it does sound a little odd, but perhaps it raises the question of what moisture content(s) would a piece of oak fascia be subject to through the course of the seasons? If at any time it reaches 30% then the ebay stuff might be ok.

 

[middi]

Biff,s point about not using KD oak for soffit or facia boards becomes even more valid especially in light of the prices you have been quoted. OK if you was building furniture or staircases but for the amount of shrinkage to be expected in the situations in which is used is more or less irrelevant. Partly sesoned oak should be perfect for the job.

You can buy planed european oak floorboards 160x22 for about £20-£22 sq M. as this is mass produced, it may be an effective and cheap way to achieve what you want.

 

[andrew gayton]

I have used green oak clapboard / weatherboard - 150mm x 25mm down to 12mm - and it shrank in width by approx 25mm; it was only fixed on the top edge though.

why use oak in this instance?

larch will go a similar silver grey left fairfaced.

 

[Penners]

The Ebay 30% stuff would, I think, give you some problems. It's just too wet. As Biff has suggested, I would use air-dried oak. The 15% - 20% m.c. will equate pretty well to the average ambient air moisture content, so minimising shrinkage, warping and cracking - although you could still get a bit of shrinkage across the grain. The important thing is that you'll get very little shrinkage along the grain.

On a board only 20mm thick, be a bit careful about using fixings to try and resist shrinkage. You could end up cracking the boards.

 

[middi]

........And use stainless or brass screws otherwise normal nails or screws will rot before the oak.

 

[electricianid]

The Ebay 30% stuff would, I think, give you some problems. It's just too wet.

That would rule out using green oak then for sure.

 

[Penners]

That would rule out using green oak then for sure.

Well, I can only say that I wouldn't use it. Just too much risk of shrinkage, cracking and warping.

 

[Willmat]

Being seriously lunatic/deranged enough to have put oak capping timbers/barge boards on a house in Norfolk, I'd recommend air dried and definitely not kiln dried or ebay swamp wood. seems the only sensible option given that if its being lying stacked at the local saw mill in the outside air/rain/moisture for years and looks straight, then chances are it will stay the same shape on your roof a few miles up the road in the same climate.

nearly all the air dried planks hardly moved at all - hardly any sideways shrinkage either. would seriously consider not using linseed oil though! think its been mentioned many times before. 3 coats washed off mine within months, leaves the oak looking black for a while until completely washed off by rain, and the hassle of spending all that time back up the ladder does not do much for me. Looks nice greying anyway and admittedly the oak does look fantastic if a little odd as no one else is mad enough to use it. Andrew's idea of larch sounds very interesting - presumably much cheaper? Presumably there are some other products if you do want to retain the freshly planed look , that other people know, that retain the colour a bit more?

 

[andrew gayton]

linseed oil 'washing off'...................? I have not experienced that one! larch, 'pound-for-pound' is about 2/3 the price of english oak.

 

[electricianid]

leaves the oak looking black for a while

I think I heard somewhere that using boiled linseed oil can result in blackening. Something to do with the additives, maybe it could be avoided by using raw linseed oil?