I am building an timber frame extension to my house, and have been offered some larch from a nearby wood.
I have heard I might have difficulty using it as it is ungraded and wouldn't be passed by building regs. Is there a way round this problem? Is it the case that all building under building regs uses graded timber, and there is no way to substitute ungraded timber. What is grading anyway - can it be done.. etc
Any advice most welcome,
John Pedersen
(GBP) Keith
posted on 09-02-06
Hi John. Graded timber should only be required where a section of the structure needs engineer design input i.e larger than normal spans for floor joists or roof trusses or rafters of non conventional design. If the building is to be multifloor timberframe it may also be necessary.
Most building regulation requirements simply go on dimension of timber and are based on historical proof of compliance as in common 'cut on site' roofs etc. If you are worried, then check with your building regs officer first but I see no problems in a typical conventional house of normal dimensions.
If you do need grading then a local mill will probably do this for you for a small fee. Basic grading is visual anyway.
Hope this is useful. Regards Keith
Paul
posted on 09-02-06
Beware that if you use lumber "fresh" from a wood, it will have far too much moisture. After it has been cut, it will need to dry out for at least a year (unless dried in a kiln) otherwise it will be useless for framing a building. I live in Canada and 95% of the new houses here are timber framed - but they use kiln-dried dimensionally stable lumber with a low moisture content.
Paul.
John Pedersen
posted on 09-02-06
Thanks for the replies.
I intend to talk to the build regs officer, but I wanted some background info first.
The trees aren't cut yet - next week. I don't intend to use them till summer at the earliest, and they will be planked to 55 mm or so and stored under cover.
I realise that the wood will still be pretty wet, but I have heard that working with green larch is easier than working with green oak - I was thinking that perhaps I might need a few extra noggins in nice and tight to counteract any twisting as the timber dries more.
But I haven't done any timber framing before, nor have I been involved in harvesting the wood fresh from the forest, so I am going on whatever advice I pick up. Any more thoughts on the practicality of using larch just 5-6 months after cutting it?
Thanks
(GBP) Keith
posted on 09-02-06
If you are building a traditional frame i.e mortice and tennon then green timber is fine.
By the way green oak is wonderful to work with, it cuts like butter. Whereas dry oak is another matter.
Traditional oak frame construction design allows for shrinkage after the frame is finished. We are reviewing a wonderful Oak frame book in the next issue of BFF magazine.
Regards Keith
Tony
posted on 09-02-06
Please don't worry too much about all this grading stuff the bottom line is "be sensible and dont use bits with large knotts or shakes in them". Though even these bits can be used up for noggins etc. And as for dry it was only a few years ago that we used to get all our timber wringing wet and it did shrink 5 mm or more in the first year and even go a bit mouldy mildew or black in the stacks -- but it is still doing its job. So nice now to look back and see how things have changed --all be it very slowly -- hopefully we will soon be able to do the same with respect to sustainable issues and look back and laugh at ourselves not recycling or choosing our materials carefully enough.
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