Oak cracks and splits

[Wurm]

I am building a set of windows out of oak for an old stone cottage. I chose oak both because it was recommended to me for being durable in a maritime climate and also because it is traditional. It is just my second woodwork project, the first having been an airing cupboard of pine.

As I completed the first window frame its base section without warning split almost completely in two along its length, and subsequent inspection of the rest of the stock found a lot of pieces had cracks and splits of a kind that in a conker would be called a 'death crack'. Trimming the ends of a piece would often result in chasing a split until the piece was destroyed.

I am disabled so ordered air dried wood from a sawmill that I found online. It sat inside the cottage, which has no windows so plenty of moisture was blowing through, for several months before being cut. Seven further deliveries from two further sawmills have produced a lot of the same problem, which has often been evident as soon as I unpacked the delivery.

Some of the pieces that appeared OK have subsequently shown problems a number of months after being cut.

In a search of this site I found talk of sealing the end grain to slow the rate of drying, but many of the problems have been far from the end of the piece, so would it be a good idea to cut and plane the wood as soon as it arrives and then apply a sealer to every face? If so, what sealer would anybody recommend? I had been intending to oil the windows once complete.

Also, can anyone recommend a book which talks about this kind of thing? I have read two books on woodwork but none went into this kind of practical detail.

Here are some pictures:

 

[MikeG.]

There are plenty of experienced woodworkers who would hesitate at taking on the project of making oak windows. It isn't for the faint hearted. Your mistake was buying wood sight-unseen, and whilst I appreciate that it wouldn't be easy for you, I urge you to find a way of selecting your own timber in a woodyard. Custard has done a wonderful job writing up a "how to" guide to buying hardwood somewhere on the forum, and I urge you to find it and read it carefully as this really isn't a straightforward subject.

 

[Phil Pascoe]

My friend said in 25 years of full time decorating he'd never come across oak windows. I dare say there are reasons why they are uncommon.

 

[AJB Temple]

Well....I have made numerous oak windows for my own properties. You seem to have left the oak to acclimatise in a damp environment, which doesn't achieve anything much. It does sound to me a bit as if you have bought green oak.

You need to be buying high quality joinery grade oak and then keep it properly dry whilst you are storing it and making your windows. You really need to select the timber so that you are buying wood that is suitable for the job and that is cut for stability. In my case I have my own supply of oak and I used rift sawn timber which I find to be dimensionally very stable. In my case it is well seasoned too as I have owned the wood for 30 years. Quarter sawn will be fine but I would not use flat sawn in this kind of application.

If this is only your second project, it may be that you are biting off a bit more than you can chew?

 

[Wurm]

I appreciate the responses.

There were a number of mentions in Custard's discussion (which I have just found in a search) of wood being dried too quickly, and I have been wondering if last year's dry weather may have caused problems for the air drying process. All three sawmills assured me that their wood was ideal for windows, and most of the pieces I have had of 2" and below have been OK, but more than half of the 2.5"+ sections have had problems.

The lack of any responses on sealing the wood suggests that it would not have helped. I had been assuming that there was no need to fully dry wood for windows that will be exposed to weather so that leaving it out of the rain would be sufficient.

 

[profchris]

The lack of any responses on sealing the wood suggests that it would not have helped. I had been assuming that there was no need to fully dry wood for windows that will be exposed to weather so that leaving it out of the rain would be sufficient.

Rather a guess here, because I don't make windows, but in essence humidity swells timber and dryness shrinks it. The movement is mainly across the grain, not along it, so the wood gets fatter and thinner, but not much longer or shorter.

If you dimension and build when humidity of the wood is high, then when it shrinks it will open up the joints. If when it's low, swelling will just tighten the joints (whether it distorts the whole thing depends on how thick the timber is, whether something like a window opening resists this, etc).

Keeping it at a reasonably steady humidity at least means that all the parts start from the same baseline when dimensioning. And for windows, I'd also guess that humidity on the low side of average (say around 50-55%) might be the best compromise to cope with the inevitable movement of the wood.

Your cracking is something different. Humidity changes might be highlighting it, but shouldn't cause this in decently seasoned wood unless there have been lots of big and sudden swings in humidity.

 

[MikeG.]

........The lack of any responses on sealing the wood suggests that it would not have helped.

Correct. Assuming of course that your timber was seasoned.

I had been assuming that there was no need to fully dry wood for windows that will be exposed to weather so that leaving it out of the rain would be sufficient.

You don't have to dry it at all, unless of course you bought unseasoned timber. Surely you didn't do that?

 

[AJB Temple]

This is why I said "it does sound to me a bit that you have bought green oak".

The splits and look of the end grain look quite typical of working with green oak or oak with a high moisture content. I use the stuff for framing and large pieces are guaranteed to split. It is unsuitable for precision joinery and I am wondering if the OP is aware of that.

 

[Woody2Shoes]

I'm wondering what sort of dimensions/shapes are the pieces that have split and what is the pattern of the grain in relation to the cross section - are you able to post any photos or sketches?

An almost guaranteed way to get most timbers to show cracks/splits is to include the pith (the "bullseye" at the centre of the tree in cross-section) in any section.

My 110-year old pine windows have (I'm almost certain original) oak external cills which remain in excellent condition. My neighbours have european oak windows - with some quite narrow glazing bars - with no discernible problems.

Cheers, W2S

PS sorry - I've just seen your photos having logged-in to post! Most of the checks/cracks visible (except the big one) in the photos you've posted have no structural significance and are probably due to quite fast drying and irregular grain pattern (with attendant internal stresses in those areas).

PPS https://en.wikipedia.org/wiki/Shakes_(timber)

PPPS https://www.classichandtools.com/acatal ... P-CAD.html (written by a member here I think) ?

PPPPS http://www.woodweb.com/knowledge_base/C ... n_Oak.html

PPPPPS I think you've used air-dried timber - a safer bet would have been kiln-dried joinery grade oak - https://www.iwood.co.uk/articles/118/oa ... ed-boards/

 

[Trevanion]

I've made quite a few oak windows, doors, frameworks etc.. and it all cracks to some degree. Whilst it is the "traditional" choice in a sense for certain parts of the window such as the cills as Woody mentioned, It's almost impossible to replicate traditional natural materials such as oak (And most other timbers such as pines) because the quality of timber is so vastly different today than it was 100+ years ago. If you take a 100 or even 50 year old piece of oak and compare it to a modern piece the differences are quite staggering really, much finer, tighter grain, straighter grown and sawn, harder, and air dried which is a process which creates a much stabler product. Whilst the more modern stuff tends to be far more coarse grained with wider growth rings, the grain direction can be very questionable because they've sawn it to maximise material rather than stableness and straightness of the material and the timber is cooked in a kiln as fast as possible to get it out for sale which causes stresses, micro shakes, and that horrible orange-yellow tinge in places.

I always try to convince people that oak isn't the best choice but once they've watched a couple of episodes of grand designs and done a little reading from some flashy salesman's website they get rutted in and that's what they want whether you disagree or not. It's very difficult to pull off oak correctly, especially green oak. I know of people that have put in green oak windows and doors in their house and the movement of the timber has caused the house to move which has cracked the plasterboard internally and done god knows what to the blockwork and lintels. I try to use the highest grade joinery oak possible if I have to make anything out of it, and it still usually has problems.

As far as books go there isn't much on more modern aspects of joinery, very little in the last 20+ years. But there is still good information in old ones concerning traditional design and techniques which may be of use.

"Modern Practical Joinery" by George Ellis; The man was very clearly a very intelligent man and knew what he was talking about. The book goes into excruciating detail about pretty much every process, it goes over the tools, machines, timbers, design etc etc... It's not just a book telling you how to do it, it's telling you why you do this part this particular way and why you do that part like that. Excellent illustrations and plates, all in all, I would rate it as almost essential reading for anyone who does conservation work replacing old windows and doors.

"Purpose-made Joinery" by E.V. Foad; A bit more modern book from the 1980s, it's a very good 300 or so page book. Filled with illustrations with some cracking cross sections, very similar to Ellis' book but 80 years newer so there have been some technological advances since.

"Cassell's Carpentry and Joinery" Paul Hasluck; Also another massive, ancient tome like Ellis' book, filled will very good information. quite rare to get an original copy but there's plenty of sellers selling reprints.

"Carpentry & Joinery" 1,2, & 3 by R Bayliss; These were more focused towards students doing their City and Guilds certificates in the 1960s and '70s, there's some very good information in them on doors and windows and it's aimed at beginners so it's all fairly simple stuff.

"Carpentry and Joinery" 1,2,3 & 4 by B Porter; Pretty much the same as Bayliss' books but there is also good information to be had in these.

"Doormaking and Window-making" by Anonymous; This one is a reprint of old booklets from the 1900s on the subjects compiled into one little, excellent book.

"Cut & Dried" by Richard Jones; A very modern book by a member of this parish(Sgian Dubh), It's not about joinery but how timber behaves. I haven't actually given this one a good read yet, just a quick flick through but the amount of information in this one is second to none on the subject. It goes through how the trees grow, what happens when it's felled, what happens when it's milled and on and on... Excellent book.

 

[Sgian Dubh]

"Cut & Dried" by Richard Jones; A very modern book by a member of this parish(Sgian Dubh), It's not about joinery but how timber behaves. I haven't actually given this one a good read yet, just a quick flick through but the amount of information in this one is second to none on the subject. It goes through how the trees grow, what happens when it's felled, what happens when it's milled and on and on... Excellent book.

That's very kind of you Trevanion. Much appreciated.

I spotted this question from Wurm yesterday, but I was reluctant to respond because the subject of the workability of oak, and the problems that can occur with the species if you're not especially knowledgeable about any of it to start with can get very involved very quickly.

The reality is that oak has a couple of characteristics that can lead to an unsatisfactory buying experience. The first is that oak is what's known as a refractory wood to dry, i.e., it's a difficult process to get, whether air dried or kiln dried. Secondly, it has an inbuilt weakness in the large, highly visible (and highly prized) medullary rays. I noticed pretty quickly that all the splits are as I expected in wurms photographs in that they are radial i.e., following the direction of the medullary rays as they radiate from the pith towards the bark.

Without going into any further technical detail (for the sake of brevity), couple the above bits of key information (there's much more regarding oak varieties) with an inexperienced buyer and user of the material, and problems such as those described by wurm are a strong possibility. I could suggest strategies for helping to reduce the likelihood of splits and shakes developing in the final product, but those strategies generally require developing experience in knowing what to look for, and knowing when to reject the piece of wood in front of you for a particular task, and knowing how to spot, for example, a near enough invisible hairline crack (the result of surface checking during drying [again generally following the medullary rays) that will open up in service, or simply split apart during the making process.

Without being party to the buying process undertaken by wurm, and not knowing the supplier, I think it would be very hard to blame the supplier, and I suspect the main problem can largely be put down to inexperience on wurm's part as, one, a buyer, and two, a user, and that is not meant as a put down. When I think back to when I started using oak more than fifty years ago, the screw-ups I made seemed to be never ending; but over the years I've got pretty good at knowing what to specify as a buyer, what to reject when it's delivered, and how to work the stuff when I've got a huge pile of rough sawn oak boards ready for the basic machining processes to be followed by the making of whatever it is that I'm making, from fine furniture to outdoor garden type artefacts, sculptural type things, and so on. Slainte.

 

[Woody2Shoes]

I think it's fair to say that - as long as it's expected and designed/planned for - movement of, and formation of checks/shakes in, oak really needn't be a problem (structural or aesthetic) most of the time. I think that most of the "defects" visible in the OP's photos could be described as "character" rather than be a "failure" - more a matter of expectations really.



https://www.castleringoakframe.co.uk/gr ... shrinkage/

 

[Wurm]

What a great resource this site is.

I guess the one remaining question is what section pieces those who build windows would recommend? The largest window is 69"W X 30"H (ironically those pieces seem in some of the best shape), the next largest are 42"W X 45"H, they are casement with a central divide. The book I read recommended 4" X 2.5" for the frame except the base which should be 4" X 3", and 2" X 2" for the window itself, but if I can get away with less it would seem to be more likely that the wood would remain intact.

I have taken the point about drying the wood and my stock is now in as dry a spot as I have available.

And I appreciate the reading list - that is exactly what I was hoping for.

 

[MikeG.]

You seem to have missed the main point, Wurm. Did you buy seasoned or unseasoned timber?

 

[Wurm]

You seem to have missed the main point, Wurm. Did you buy seasoned or unseasoned timber?

I was assured that they were properly seasoned by the sawmill.

 

[Sgian Dubh]

PPPS https://www.classichandtools.com/acatal ... P-CAD.html (written by a member here I think) ?

I've only just spotted that this link points to my book, Cut & Dried, W2S. Just to say I appreciate the recommendation from you. The descriptor (synopsis?) for the book at that link was written by Chris Schwartz I believe, although it's possible it may have been one of his team of editors at Lost Art Press that work for and with him on the books they publish.

Anyway, thanks again. Slainte.

 

[HOJ]

Wurm, I work in Oak, a lot, If its any consolation I have attached a picture to show that you just never know what you will find.

This board didn't show much evidence of a full through shake, however the grain was wild, when I cut the board it just fell to bits.

Fortunately, I always cut the biggest pieces I will need, first, and in this case it paid dividends, as I went on to make use of what was left, elsewhere.