Green oak strength class - for timber framing

[dom]

I'll shortly be building a new internal mezzanine and considering ammending the original building control approved design - to use traditional green oak post and beam construction.

I have a very reasonably priced supply of green oak beams - my question is how do I get them strength classed for structural purposes?

Standard tables for the typical structural performance of various hardwoods are readily available, and I think it's customary to derate green oak by a third - so beam calculations are straightforward.

But what about actaully getting the beams appoved to a strength class?

Do I need to get someone qualified to visually strength grade timber in to inspect and mark them?

Is it possible to rent/improvise the kit to do defelection tests?

Anyone got experience of getting structural green oak passed by building control?

[Donwill]

Try getting in touch with the "Centre for Alternative Technology" Nr Machynlleth, they might be able to help.

Regards Donwill

[Rick Hughes]

[Weatherlawyer]

No experience per se but timber is fairly easy to grade and the tables you talk about should cover the method in the intro. It just concerns live knots which I think are acceptable through most of the section (not sure) and dead knots which must not be closer together than so and so a distance and not extend beyond a smallish fraction of the cross section.

Live knots tend to allow the timber to bend or rather cuse the timber to bend when it dries. This can be mitigated in construction by removing a portion for a housing joint say, or putting the timber in a place where it won't matter or can be countered.

If you were making a piece of furniture with a live knot in it, you might want to cut that board through the middle of the knot and turn one piece around before glueing it back together, to make one side pull against the other.

With dead knots you have to cut them out or do something drastic. You might be allowed to scarf them. Again it depends on how you use the timber. If you use section that is well over size it shouldn't matter much.

Look for more sites like this one:

that the outer layer of oak is not very good quality timber and may rot away in well under a couple of centuries if you are not careful. This is why a tree is not very valuable but quality timber is. It's not what you have but what you have to throw away.

[Andy Dingley]

In oak ?

Is there _nothing_ on which you won't pontificate from utter cluelessness?

The whole business of "strength class" is entirely bogus for green oak anyway, Oak needs a framer who knows what they're doing, not this "all labelled timber is identical, assemble it by numbers" approach. As you're basicaly doing this to keep a BCO happy, ask them how much they need to know.