Treatment of a log cabin – Customer Question
I always try to offer the best advice I can and sometimes, although I recommend our Timber Treatments I do also recommend others to give customers a choice.
A customer wrote to me following our email exchange:
I really appreciate the extra detail as I certainly want to get things right – it’s very good of you to pass on your experience. I have tried to research this online but it’s surprisingly difficult to find good simple advice for a complete novice. A step by step guide “painting a shed for dumb asses” would probably clock up a lot of hits on your site! 😉
I have enough information to make my own decisions now and understand how important the base\DPM and ventilation are.
I’m not going to write such a blog post as suggested for ‘dumb asses’ but it might be useful for you if I copy my email to Mr M that prompted this reply … it does go on a bit but may help with further treatment questions and your understanding of it.
I tend to advise the simplest option – three coats of something expensive. Don’t use ………. on it’s own, especially their shed treatment as it’s terrible for log cabins.
For the first few years of life of a log cabin overkill is a good thing. The wood is kiln dried and I have a personal theory that because it is, the straws that make up wood are still very open, the wood is not really dead as dead should be, it’s an artificial death that we’ve forced on the poor tree.
It’s this openness that allow moisture from the surrounding air content to be absorbed and expelled quickly. Wood is basically made up of loads of straws (needed to suck up moisture from the ground) and it’s these straws we want to bung up. a good few coats of a good treatment does this and there’s never a problem.
Ideally timber should be air dried, But, if we did that you would wait years for your log cabin / table / worktop / kitchen etc and no one wants that.
A cheap treatment won’t stop the transfer of this moisture, there isn’t enough thickness to it to stop the moisture flow. If you use something cheap she will expand and contract a lot in the first year.
Second and third year you will not see it as much, this is because I think the straws have collapsed slightly and / or bunged up. The wood is also more dead and starts to behave more like air dried timber with less movement.
If a building is well ventilated a preserver is not necessary. If a building is not treated at all but is still ventialated it will not come to harm either please see this old girl who has never been treated: http://www.tuin.co.uk/blog/log-cabin-treatment-panic/ (some expected patterns of bahaviour though)
Timber treatment and what is recommended by me, the producer, the treatment supplier all have different reasons.
From my point of view I don’t want a complaint from you next year that your building has expanded / contracted and you have a gap somewhere or white bits showing. Of course this is what wood does, it expands and contracts and if a customer understands this it is never a problem, gaps will only appear if it is restricted by a window or door frame being held in place. But your cabin will move quite a bit over the first twelve months.
Sometimes though we see something else: This year we had a problem with one of our show buildings, when the Spring hit, one side contracted quicker than the other due to only one coat of treatment being applied and the sun very, very strong on just one side, the other was in total shade. It meant the straws hadn’t been blocked enough so expelled moisture far quicker than the other side that was shaded. I knew what the problem was and sure enough a week or two later everything was equal and another coat applied and no problems again.
This is why we say 80 – 120 microns depth of coverage, this is also what all the good and expensive treatments will give you. This is why they all say 2 – 3 coats and this is to make sure the depth is thick enough and closes the straws and stops uneven movements.
So, we’ve blocked up the straws which is my consideration and so I don’t have to speak to you next year when you tell me about expansion and I have to explain it and moisture content in the air: http://www.tuin.co.uk/blog/depth-of-treatment-and-moisture-content-in-wood/ and why your cabin is behaving this way.
Next we can move onto the producer both he and I know for certain that wood will never rot if allowed to ventilate. But, we have to account for a dodgy base, water sitting at the base, foliage up against it, insects eating it, bird dropping introducing fungi, no damp proof membrane etc and this is why we will want a preservative. This will stop and inhibit anything forming should a customer be a bit of a numpty and not realise this themselves. This will stop you speaking to me in about 5 years time.
Then we come to the paint / treatment manufacturer – They will be wanting to cover their butt. They will want overkill, belt and braces and will ask you for everything, the same as we should do. If anything happens they will want to ensure you did everything correctly. They also know that wood doesn’t rot if ventilated but also want to watch for the errant customer. If everything is done correctly, no matter what you do to timber it will always be fine. But, if it is exposed to wet and not allowed to ventilated very regular treatment needs to be given.
If all of the above is understood, and the inherant nature of wood is understood such as expansion, contraction, cracking, splitting etc: http://www.tuin.co.uk/blog/cracking-and-splitting-in-timber/ then a good quality treatment is enough, two to three coats applied the building will look good for several years before re-application (mine was using S—— years ago, all I do is pressure wash it yearly, it could do with a touch up but it’s still rot free) If though it is wet constantly then more considerations need to be made to guard against rot caused by damp or infestation.
My advice is good ventilation, a good base and a DPM is the most important thing to give a log cabin a good start in life.
From then on a good treatment of about 2 – 3 coats, ideally something that does it all without under preservatives for ease. Something that looks good and you don’t have to re-do for a couple of years. (our treatments are very good by the way!) Remember what wood does naturally and enjoy it. Bear in mind though as well, one of the reasons why we buy a good treatment for a log cabin is the elasticity, the bloomin’ things move and this elasticity does help a lot especially in the joints over the first year and is very important, cheap treatments will not give you this.
I hope this has helped?