Green oak advice

[mpooley]

I am about to start building a conservatory on an old barn conversion and the design is post and beam oak.
I assume one must/should use green oak ?

I havnt even looked at suppliers yet and have never worked with oak like this before is there any advice you can offer please?

some Post and beam buildings use Douglas fir I am told.

I assume this would be easier/cheaper than oak?

thanks
Mike

 

[Pecker]

Mike, I am no expert in this, but have had some dealings with green oak.

It moves a hell of lot during drying, which can take several years. This leads to shakes and cracks which some customers object to/think is a fault.

It rusts and blunts your tools something chronic! keep them well oiled,clean and sharpen afterwards.

It's flaming heavy - and I do mean heavy!!! - my fire place has a piece of green oak over it. 12" x 6" x 5ft. It took two of us to lift and position it (30 inches off the floor) with a third person to actually get it in the exact position needed.

It is hard to plane/sand due to the densityof it, but that may vary a bit by type.

When I last looked at Douglas Fir ( a good while back), that too was very expensive, though not quite to Oak prices. DF can be as tough as old stringy boots at times, so choose carefully. It would probably work out cheaper though and should dry out a lot quicker. I would also guess it to be a lot lighter?

Woody

 

[Alan Smith]

AS woody says green oak moves a lot which means that if you do use it as a frame you will have to isolate the glazing system from the oak otherwise the glazing will fall out or crack as the oak settles. If you are set on oak how about using salvaged oak beams which will have done their moving a long time ago. There is a pretty healthy trade in these nowadays, in fact a fellow up the lane from me (West Sussex) is importing beams and whole buildings in from France.

 

[lurker]

I remember reading a good article on this by, I think, Keith Smith. You should find him over on the dark side.

 

[jasonB]

Green oak will be a lot cheaper than Douglas Fir or reclained oak. They do a lot of timber frame construction using the D.Fir in American where it is not so costly.

Reclaimed oak will be very hard and therefore difficult to work, green oak on the other hand will be like cutting a good hard cheddar cheese if your tools are good and sharp.

If you are using standard size sections then the imported G.oak will be cheaper than having native oak sawn and there is little difference between the two.

As has been said the tannins in the oak will turn your tools and your hands black but that can't be helped. Invest one or two framing chisels or the Axminster all steel ones work quite well and a SDS+ drill to take a 20mm auger bit, this can be used to remove most of the waste from the mortices an also drill the peg holes.

Weight is an issue as the sections get larger, I had to use a mini digger to lift the fresh cut 8x8s for this deck but three of us errected the frame for the small barn at the bottom of page which was 6x6 that had been sawn a few months earlier.

This book is worth getting.

Jason

 

[mpooley]

Thank to you all for your helpful replies

I have just been to a local woodyard where he has tons of 3yr air dried oak which he recomended to me for this job.

It looks good stuff and he gave me a 6x6 bit to try out which i have just done.

I must admit that i was amazed at how easy it was to saw - chisel and rout !!

and as this wont move so much as green oak i think i might get this. He wants £27.80 per cu/ft .

what do you think?

Mike

 

[jasonB]

About £10 more per cube than green, whats the total volume you need?

Jason

 

[mpooley]

About £10 more per cube than green, whats the total volume you need?

Jason

approx 100cu ft :shock:

 

[bob_c]

Id be careful using oak air dried for only three years,if the sections are thick it will need alot longer than that to be more stable.Usable for timber framing but id be apprehensive for using it with glazing.
Ive just used a load of air dried 4 yr oak which looked fine but started moving alot once i started cutting and machining it.

 

[mpooley]

Id be careful using oak air dried for only three years,if the sections are thick it will need alot longer than that to be more stable.Usable for timber framing but id be apprehensive for using it with glazing.
Ive just used a load of air dried 4 yr oak which looked fine but started moving alot once i started cutting and machining it.

Ta
I think i can isolate the wall glazng from the frame ok - but apart from loads of silicone i cant think of how to do that on the roof.

so what do you think i should use, kiln dried oak?

Mike

 

[jasonB]

For the roof you should be able to get suitable patent glazing bars that can fit to the top of the frame. These will have suitable gasgets and cover strips.

You are unlikely to find much kiln dried 6x6 oak even if you could afford it, the thicker it is the longer it takes to dry so you are paying for kiln time.

If you did use kiln dried it would still move as the external surfaces take up moisture from outside. A bit of googling will find suitable glazing methods that allow for movement in the oak, like this The face fixing method is easy to do.

Jason

 

[mpooley]

Ok thanks - will do

I have spoken to the people in your link and they are quoting approx £200-£225 per sq mtr for them to fit all the glass - not sure if i want them too as this will cost approx £13000.00 eek!

so what is the consensus of opinion then

kiln dried oak no good/too expensive?
green oak with special glazing bars?
wickes plastic conservatory eek!!! lol
?

thanks for all advice. it really is appreciated as this is going to be a big and expensive project which i dont want to cock up!

Mike

 

[milkman]

Green oak construction is an interest of mine although I only have experience via courses and some limited work at a framing yard so I won't pretend to be an expert.

I've worked with oak and douglas fir and while the oak was a dream to work with, the douglas fir is a bit less over the top for a conservatory (does one need a conservatory to last 300+ years?).
I don't know what the price difference in green oak and green DF is but the latter must be cheaper. Cost was a major reason for its use in the project I worked on.

Don't worry too much about oak tannin and tools, just a wipe will do but use a barrier cream on your hands as tannin can cause sensitivity in some people.

The checking and moving should matter less in a conservatory as its not well heated, anyway if you don't like checking and cracking you shouldn't be going down this route… just build a Victorian conservatory instead (the plants will like the extra light too!)

Yes green oak is v.heavy! You need an extra person on hand when moving or turning the posts, a heavy duty trolley helps for moving stuff and heavy duty trestles as well. You may need several people around for the raising or a "roustabout" (telescopic lift) or a ginpole or if its really huge, a telehandler or crane.

I think the Jack Sobon book uses the square-rule setting-out technique used in N America on straight softwood, not windy european oak. This harder to pick-up than mill-rule/ scribe rule traditionally used here.

http://www.wealddown.co.uk/Courses/courses-building-conservation.htm#bc timber scratch do very good courses in this type of building and lots of info can be picked up. You build a 10' square single bay. Not a cheap course though.

A guy called Henry Russell does one or two courses each year and packs in a lot of info. He's very good and you should be able to find him via http://www.carpentersfellowship.co.uk/

Finally if you fancy someone along for the ride PM me as I love any excuse to get out my framing chisels!

 

[Jake]

I believe that you can't really kiln oak above 4" thick, and its more usual not to go further than 3", as it tends to honeycomb.

 

[les chicken]

Have you thought about using sweet chestnut, very similar properties to oak but lighter and more stable.

Les

 

[mpooley]

Have you thought about using sweet chestnut, very similar properties to oak but lighter and more stable.

Les

Hi
No i hadnt thought of chestnut!

although a friend has a place in france and they use a lot of chestnut there and his frames have a tendency to go black!

mike

 

[Pecker]

I believe that you can't really kiln oak above 4" thick, and its more usual not to go further than 3", as it tends to honeycomb.

Jake, I beleive you're right. I had to enquire about some 6" x 6" green oak being kiln dried. I was informed in order to do that, they have to drill a hole along the length of it so the moisture can escape. I remember asking (I think it was on here) at the time and a couple of people said the same thing.

woody

 

[milkman]

Sweet chestnut has a tendency to twist sand get spiral shakes but I do know of someone who built in it, said it was very good to work with and yes lighter.
I can't see that it would be anymore stable than any other green material, its going to shrink as it dries.
Its rarely if never used here historically although I don't know why, perhaps its the above so oak was used as they didn't have to think about it too much

There was an italian restortion build on Grand Designs that mentioned extensive use of chestnut there although you can't get the sizes any more for what they were doing. I think the restoration architects were insisting they stain some oak to a chestnut finish so it would look authentic much to the consternation of the owners.

Re: the glazing thing, I went to a lecture on this and I think they said they you face mount the glazing to the frame and use battens to hold it on with lots of silicone. Another solution would be to cut channels in the frame with plenty of room for movement although your glazing would be locked in there with the frame.

Wish I'd takren notes!

 

[RogerS]

.......
I think i can isolate the wall glazng from the frame ok - but apart from loads of silicone i cant think of how to do that on the roof.

Mike

Silicone? Modern materials? NOOOOOOOOOOOOOOOOOOO!!!!!!! Guaranteed to make it rot. Oak timber buildings need to breathe. The old ways are still the best way...if you need to fill in holes etc then use lime mortar. I am renovating an old timber framed black-and-white. Where they used silicone and Portland cement mortar to patch up holes, the oak is rotten. Where they used lime mortar, the oak is rock solid.

For cutting the oak buy yourself a bow saw with a raker blade. Bahco do quite a good one. For internal beam work I used a Machine Mart cheapie planer/thicknesser to take off the rough edges and it's lasted pretty well.

Lastly, when experimenting in your workshop as to the best way to cut/rout/hack green oak, do not...repeat do not...leave the offcuts on top of your cast iron tables DAMHIKT.

If you have some really large sections that need elevating then hire a Genie Lift (I got mine from Travis Perkins).

 

[RogerS]

Mike...I'm getting terribly senile in my old age.

I completely forgot that my workshop was made out of green oak. Here you can see the windows. Each window is double-glazed K glass and about 2m high x 1m wide.

The windows were inserted into a smaller cross-sectional wooden frame that accomodated three windows. This wooden frame (also green oak) was then fixed inside the main heavy-duty oak frame of the workshop. The windows were fixed using glazing silicone. A generous margin was allowed for between the windows and the frame. These were built four or five (maybe even longer) years ago and no breakages apart from one that has cracked. I'm not convinced that the cracking was due to to wood movement though.

Now, I may well have been fortunate to have no other cracks because the main structure of the workshop is separate to the wooden glazing frames. If you're using your green oak as combined structure and window frames - possibly for aesthetics and elegance although given you're adding this on to a barn conversion you could get away with chunkier structural frames for the conservatory- then you might not be so lucky.

The original 'expert' who made the main frame made so many errors that I can now see in retrospect. Originally the window frames were just held on to the main frame with metal brackets...gaping gaps...loads of water ingress. A friend of mine who is an expert in oak buildings (new and old) helped me fit the window frames properly. Have you ever seen anyone rebate greenoak with a chainsaw? That's what he did to allow the window frames to sit better.

PM me if you want to know more