Timber basics article

[stuart noble]

Just a couple of points. Since these 2 species are what most people end up with, I thought a little more detail might be appropriate. Use anything you like and dump the rest :-)

Basically the Christmas tree, Picea abies. Mainly used for 150mm x 25mm flooring because it is reputed to be more stable than redwood, and is a good deal cheaper. Its use in other fields is restricted commercially because a) it has a woolly structure and is difficult to machine to a fine finish, b) it dulls cutters, and c) the knots are unstable. However, the better grades are uniform, virtually knot-free, and useful where a pale colour is required without the obtrusive orange look of redwood. An underrated timber for interior work IMO.

Redwood (European redwood, Scots Pine) *should* always be pinus sylvestris. It forms 90% of the stock of most timber merchants, including the vast majority of mouldings, architrave, skirting etc. Quality (and price) depends on how far north it's grown and, since the average customer has no way of assessing this, using a reputable merchant is the only guide. All redwood is "kiln dried", that is to say it's dried at source to an

*average* moisture content of 17% ("shipping dry") to prevent blue stain and other fungal infections. Technically this makes it unsuitable for interior work in a modern, centrally heated house where a content of 10% or less would be more appropriate. Leaving it in the building to acclimatise is obviously recommended but the drying out doesn't happen quickly. Depending on the amount of material, it can take several weeks for, say, floorboards to reduce across the width.

Buying either of these species from the sheds isn't recommended. In the case of whitewood I'm not even sure they haven't discovered some new, truly appalling species that they're allowed to call "whitewood". I'm a real cheapskate but shed timber represents poor value compared to a pukka merchant IME. Also, the likes of B&Q simply don't have the facilities to store timber, which should be kept under cover but in outdoor conditions. The shrink wrap compromise doesn't seem to work very well.

[meow2222]

I think what was written has been misunderstood, I'll try to clarify it. Thanks

NT

[Tony Bryer]

Nothing to do with law: having to label stuff in metric units is relatively recent (? last 10 years) whilst I am fairly certain that plasterboard and chipboard went to 2400mm from 8' around the time I started doing serious building projects 30 years ago, likewise the metric dimensioning of timber. Also note that a 2.4m length of timber is 2.4m, not an 8' (2438mm) with a metric label.

[John Rumm]

Still wants to be 4x2 to follow UK convention.

[The Natural Philosopher]

As a scholarly epistle this fall far short: you make many generalisations that are not always the case.

e.g knotty timber is sometimes preferred in joinery for aesthetic reasons, to name but one.

However as a rough guide to someone who knows nowt about timber, its better than nothing by a fairly large amount.

Rather than go into horrendous detail I would say simply prefix the section with a warning that it IS 'generalised' and further information etc etc.. is available in more detail from specialised sites.

In particular issues to do with warping and wood movement ignore the fact that *all* wood moves under humidity changes, and its the actual structure of it and the way its cut that determines how it moves - warps, bows cups and so on.

And unless you use something like structural steel to constrain it its likeley to be stronger than anything you can throw at it when it wants to move.

i.e when using wood in a structure it WILL move. Forever. Unless you are not using it as the primary structure when it gets bolted or glued to something more massive. e.g veneering onto stable substrate.

The only way to get wood to adopt new shape permanentely is via steaming and/or ammonia treatment. Beyind noraml D--Y usage.

Ergo I would not tell people how to TRY and strighten wood. If it aint straight cut it into bits that are, or throw it away, or use it where it really doesn't matter.

[meow2222]

OK. I was thinking more about problem movement than all movement. I think that level of detail would be good for a timber article rather than timber basics. Maybe that'll come next.

NT

[The Natural Philosopher]

Yep. I thnik that as a basic D-I-Y intro to lumber the article was pretty good, its the danger of stating as facts things which are more complicated than they appear and not in every instance true, that is the constant bugbear of anyone trying to distil a complex subject into a simple guide for the fairly ignorant.

Its a bit like "I before E, except after C" .. which has so maney execptions, but is still useful, so you add "as long as the word, sounds like the sea.."

Which is better, because rein, deity. reification and the like are now correctly identified...

But then you get 'ceiling' and 'seize'

So once again its in the ultimate analysis down to individal cases, and no general rule that is universally applicable.

The more I workd with wood in a structural context,the more I realise how much there is that I am either ignorant of, or not sure about.

Take the statement about heartwood being rot resistant, and the pith never. I can't say that has been my experience at all. Ive got firewood cut and left in the rain for years, and its rotten all the way through with very little discrimination between the parts. POSSIBLY the outer rings rot a bit faster than the inner.

Other useful things in understanding wood movement are that after first drying down to average internal humidities, you can get something like

1% variation along the grain, about 2% in the direction of the original radius of a trunk, and abuut 3% tangential or circumferentuially to the bole. THis allows you to dentify wood that wont cup (quarter sawn .Even close surface grain) from planks that will (flat sawn with wide wavy grain patterns). In addition wood that has grown laterally from a tree (check for rings closer underneath than above - and eccentricly placed heartwood, in effect) will always show differentlial mopvment between almost any tow parts. '

Going from green to dry is something like 4 times all of those..

Wood left on a building site - e.g. rafters stacked outside and put up and left for a period before being covered, even if dried OK in the first place, will still shrink by around 30% of green values once in place.

I know you will hate me for saying this, but by and large I eschew real wood for major structural work wherever possible, and use composites like PLY or MDF or chip or indeed steel, to make structural elements. Wood is lovely and decorative, but the art of getting a structure that allows movement is fairly rare in carpentry, though known to most of the better joiners and cabinet makers, and it takes time and money to produce and attractive wood structure than wont shift and move to the point of visible warping cracking or breaking of glue joints etc.

I thoroughly recommend Hoadley's 'Understanding Wood' as a book that perhaps you should read cover to cover, and then try and distil the main points down into a wiki. It's where mosts of the info quoted here comes from, and its also one of the best books I know on the properties of wood as an engineering material, and practical guides to using it in that context, as well as having some excellent tables. Sadly I gave my copy to one of the carpenters who built my house, as a Christmas present. I haven't replaced it yet, but I will.

For anyone going beyond just whacking up some rough sawn 2x4 for studwork, its a must.

His anecdote about rolling marbles on a kitchen worktop build with wet timber framing (accurately) after it had dried (no longer anything like level) is significant...

[Pete C]

Good article but:

When timber is sold as 'finished size' the stated size is what you get'

'Some large timber yards have a thicknesser for planing timber to a required size'

'With small mouldings and 'stripwood' the stated size is usually what you get.'

cheers, Pete.

[Pete C]

I would just say:

'Where all timber needs to be absolutely straight, most reputable timber yards will allow you to hand pick wood for later delivery'

and follow with:

'Bent stock is rarely found at reputable timber yards, but can be more common at discount DIY retailers.'

BTW where do you buy your wood meow? ;)

cheers, Pete.

[Pete C]

Couple more points:

Whitewood is usually spruce.

Whitewood is generally characterised by having a larger number of larger knots, and the end grain shows growth rings that are wider (Wider growth rings indicate a faster growing timber).

Redwood is usually pine.

Redwood is characterised by a smaller number of smaller knots, and the end grain shows growth rings that are narrower. (Narrower growth rings indicating a slow growing timber).

BTW some pictures in the DIY wiki may help illustrate different types of timber.

cheers, Pete.

[stuart noble]

There are over 100 species of pine, most of them commercially available as timber.

[geoff]

The NP going on about spelling rules ?

Now I've seen everything ...

[Rod]

I thnik (stet) he knows how to spell - but not how to get his fingers to type what they should. Just like me - except I do try to go back over and correct what I notice.

[stuart noble]

I believe there's a new fangled invention called a spell checker

[Dave Liquorice]

Eye halve a spelling chequer It came with my pea sea It plainly marques four my revue Miss steaks eye kin knot sea

Eye strike a key and type a word And weight four it two say Weather eye am wrong oar write It shows me strait a weigh

As soon as a mist ache is maid It nose bee four two long And eye can put the error rite Its rare lea ever wrong

Eye have run this poem threw it am shore your pleased two no Its letter perfect awl the weigh My chequer tolled me sew.

[The Natural Philosopher]

Best post of the day.

FWIW my spelling is around 99.8% good. My typing is around one missed key in six. Not helped byfag ash in the keyboards.

Sometimes I can't be bothered to correct it.

[meow2222]

Thanks to everyone for pitching in. Here it is

points made that weren't included I hope to include at some poin in a more in depth article.

cheers, NT