Air dried oak for outdoor chairs?

[bjm]

Hi Richard

The point I was trying to make was that I wouldn't consider wood at 20% to be thought of as 'dry'. For many woods fsp is ~25%mc.

There are two general types of wood decay wet rot and dry rot (ignoring soft rot for now). Wet rot does need a source of moisture to become established from spores and there will be a time lag where it will be competing for resources from other organisms. Decay does not initiate immediately so intermittent wetting is rarely a problem so long as the wood dries out fairly quickly. Decay only takes hold once the conditions are 'right' for the fungus.

Dry rot is a special case because, if established nearby (out of sight), it can grow and infest wood that is, to all intents and purposes, dry (in the region 10-16% depending upon ambient conditions). This fungus has the ability to transport moisture through it's hyphae to the growing front where decay is active - it doesn't need to re-establish itself from spores like other wood decay fungi. This is what makes it such a problem to remedy as you have to remove all the hyphae you can see, and then some! Ventilation is a good remedy because it doesn't like draughts and there are companies out there that treat dry rot by controlling the environment rather than using chemicals. There was a paper published about 30 years ago where they discovered that Protestant churches were less susceptible than Catholic churches to dry rot due to them being used during the week and disturbing the air too much for the fungus to get hold! (I'm recalling this from memory so may not recall all the details, or have the denominational susceptibility correct! - I will try to dig out the reference but I haven't worked on this for 20+ years now). It's an interesting fungus to work with.

The term 'dry rot' has been appropriated to cover all forms of fungal decay but the reality is far more interesting.

As I understand it, much of the wood we used to buy from across the pond used to be only partially dried on the assumption that it would dry down during the long voyage!! This would have been back in the 70's and is no longer the case today.

 

[Woody2Shoes]

I've drawn up my plans and cut my templates.
So I have run out of displacement activities and have to commit to buying timber.
Outdoor chairs - I'm thinking air-dried (no point in kiln dried I guess?) and oak (as they'll be out in all weathers; with an Osmo UV finish. Is that sensible? I've never done outside stuff before. I have seen comments about iron and oak so will be careful re. screws.

As any timber is going to have to be delivered (I need about 15 cubic feet all told), any recommendations for source? I've a couple of quotes at £50-60/cubic foot (for 1" and 2" waney slabs); what's the goinig rate?

Finally, what about glue? Cascamite or something better?

I'm going to do a prototype in pine to try to make sure the design works and weed out the worst of my mistakes!

Any other advice glady received (apart from "go to Ikea" perhaps).


Thanks!

My 2d's worth:

a) I'd try and design out metal fixings and glue to the greatest extent possible - use drawbored pegged or wedged m & t's instead
b) I wouldn't bother putting finish on it - you'll forever be sanding it off and re-applying - I'd just let it weather down naturally.
c) Sweet chestnut (try a supplier in Sussex or Kent, which is where most of it's grown) or oak would be fine. You're buying relatively small quantities by most suppliers' standards so you won't get a big discount off 'list price'. For tight joints relative moisture content (male piece drier than female) is all that really matters.
d) Rot will tend to occur on those parts in contact with the ground (feet) or where water can collect (non-through/blind mortices that can't drain) so 'defensive detailing' is a good idea.
Cheers, W2S

 

[Sgian Dubh]

... This is what makes it such a problem to remedy as you have to remove all the hyphae you can see, and then some! Ventilation is a good remedy because it doesn't like draughts and there are companies out there that treat dry rot by controlling the environment rather than using chemicals. There was a paper published about 30 years ago where they discovered that Protestant churches were less susceptible than Catholic churches to dry rot due to them being used during the week and disturbing the air too much for the fungus to get hold! (I'm recalling this from memory so may not recall all the details, or have the denominational susceptibility correct! - I will try to dig out the reference but I haven't worked on this for 20+ years now). It's an interesting fungus to work with.

The term 'dry rot' has been appropriated to cover all forms of fungal decay but the reality is far more interesting.

Brian, I suspect you either have, or used to have a particular interest in fungi, and it wouldn't surprise me to find you have connections to an organisation such as BRE, or some other research facility. I too have an interest in the subject, but primarily from generalists perspective of fungi within the broader field of timber technology and how it has an impact on woodworking.

Your responses have been interesting and informative, and I'd be happy if you can find and share that reference to drafty/becalmed Catholic/Protestant churches. Slainte.

 

[bjm]

... I'd be happy if you can find and share that reference to drafty/becalmed Catholic/Protestant churches. Slainte.

Hi Richard - somewhere I have an extensive list of literature on the subject - just not sure where to start looking at the moment. You may have to be patient!!

 

[RobinBHM]

I would suggest irony rather than oak (maybe Iroko -thks cabinetman)
Oak is likely to leach tannins and could stain skin or patio.

Oak is prone to surface checking, which could be a problem.

I would recommend cutting your timber to rough sawn sections, then leave outside, but covered for a few weeks. If you make with killed dried timber without conditioning there be significant movement.

 

[Cabinetman]

Robin I think your proofreader needs a kick up the bottom, no doubt you meant Iroko and kiln dried or maybe not!
But you certainly should have a bit more time on your hands now, that other thread must’ve been exhausting.

 

[luke burgess]

Any objections to a black finish? air dried durable timber, european oaks grate!
My understanding is that the heat of the kiln process kills ensigns that protect the wood from the bacteria that cause rot,more relevant than moisture content.
just made some furniture for a client who's renovating a 16th century barn.
The builders doing the ground works showed me some old adzed oak post they dug up'
the subterainion section had been burnt to preserve, scrape below the blackened part and the wood below was in perfect condition unlike the portion above ground that had rotted away,not supprising after centurys of yorkshire weather.
So we burnt the table and bench frames we had made in homage to those old posts.
sanded them to 100 grit and hit them with a blow torch, let it cool down,wipe down withe white spirit to remove lose charcoal and sealed with oil (to protect clothing more than anything) Apparently the technique is used to preserve softwood houses in Japan.

 

[bjm]

...Apparently the technique is used to preserve softwood houses in Japan.

Yes, it's called Shou-sugi ban. There are also theories that it provided a degree of resistance to catching fire but I'm not (entirely) convinced? The protection it provides effectively comes from lowering the moisture content in the charred sections - the hydroxyl sites in the cellulose, where water binds to, are destroyed. This is also the basis on which modified woods work. The post you dug up was, more likely, protected from decay by being too wet - the charring obviouly didn't protect the wood above-ground.

 

[RobinBHM]

Robin I think your proofreader needs a kick up the bottom, no doubt you meant Iroko and kiln dried or maybe not!
But you certainly should have a bit more time on your hands now, that other thread must’ve been exhausting.

Oops

Ive recently started using an ipad, I really cant get on with it, I used to use a Samsung with android

I shall edit!

I was rapidly losing interest in the other thread, cutting through the endless logical fallacies becomes tedious.

I do owe an apology to Bob, who made a valid point about gdp forecasts - I had made a claim which was wrong, I had done some research and had drafted a response, but too late.

 

[Lightning bolt]

Another fantastic timber, cheap & wonderfully smelling for outdoor use is macrocarpa (Monterey cypress) if u can get ur hands on it. I use it all the time, love the stuff, only draw back is big knots. The most underrated, under used timber I know of!

 

[Lightning bolt]

Ps: it's durable like cedar

 

[Sgian Dubh]

Hi Richard - somewhere I have an extensive list of literature on the subject - just not sure where to start looking at the moment. You may have to be patient!!

Well, I don't wish you to spend too much time looking. If the reference isn't readily available (easily found) and then needs scanning and processing in Photoshop or similar, it's probably more bother than I want to put you to. However, if you know the author's name, or can recall the paper's title, it's possibly been digitised and already out there on the internet. I was just intrigued by the the subject matter, but it's not the end of the world if it's hard to locate. Thanks. Slainte.

 

[bjm]

Well, I don't wish you to spend too much time looking. If the reference isn't readily available (easily found) and then needs scanning and processing in Photoshop or similar, it's probably more bother than I want to put you to. However, if you know the author's name, or can recall the paper's title, it's possibly been digitised and already out there on the internet. I was just intrigued by the the subject matter, but it's not the end of the world if it's hard to locate. Thanks. Slainte.

It's piqued my interest now! Just PM'd you.