Oak garage doors, how dry the oak?

[opener]

I've just received the order to make 4 pairs of garage flb doors in oak and I shall be ordering the oak on Monday morning.

Each leaf is approx 2.4m x 1.2m and I am going to use 5"x2" for the door stiles and top rails and 5"x1" for the tgv boards.

The oak is to be left completely untreated and I'm trying to envisage the amount of shrinkage and swelling to allow for. Also is there a grade of dryness between kd and air-dried? Air-dried is too wet and kilned is too dry.

I'm sure my timber supplier (Timbmet) will be able to tell me but perhaps you can help me so that I'm prepared.

Also what allowance would you leave between the door stile and frame, and between the t&g boards so that they wouldn't jam together now or leave daylight in the summer?

Thanks in advance
Malcolm

 

[Rich]

Hi Malcolm, sorry to be a bore but what does FLB stand for?
Regards, Rich.

 

[opener]

Sorry, flb means framed, ledged and braced

Malcolm

 

[Rich]

Thanks Malcolm, fully understood and registered for future reference,
Regards, Rich.

 

[jasonB]

I would go with air dried if buying sawn boards, sould be dry enough not to start shrinking & craking but not so dry that it will start swelling.

Have you considered buying the boards in with the edge already moulded on. The guy I get my oak from keeps 22mm thick finished boards that are already T&Gd and have a bead on them. They come in from france as kiln dried but he keeps them in an open sided barn so the MC is about right and they work out a lot cheaper than machining them yourself. Should be able to get something similar in your area.

Jason

 

[opener]

Thanks for the replies.

I'm starting to be swayed by the air-dried argument if I can get it WELL air-dried.

I can't find anyone in my area stocking moulded boards but I'm a bit of a control freak so I don't mind doing them myself

Any further observations gratefully received.

Cheers
Malcolm

 

[Sgian Dubh]

I'm starting to be swayed by the air-dried argument...Cheers Malcolm

You should because kiln dried stock at 8-10%MC is far too dry for doors that will experience external RH conditions; if you use American woods they will have been dried to 7% MC.

The exterior face of garage doors in most UK locations will experience RH between about 70% in the summer to an average of about 85% RH during winter. This equates to wood MC of between roughly 14% MC and 18% MC. This could be compromised by the door's orientation. If they get a beating from the sun because they're south or south west facing they'll dry out more and there'll be a greater range of MC to consider.

Inside the garages, if they're not insulated or heated in any way, the RH conditions will be 5% or 10% lower than externally all year.

For this application you'll probably be best to use material that's about 17% MC, or a percentage point or two either side of that figure. This falls in line with the standard BS EN 942 1996 Class J30, where 15% to 19%MC is recommended for, "Buildings with poor insulation, single glazing, minimal or no heating, etc. E.g., Barns, sheds, rarely heated workshops, churches, etc," (which is my own quotation.)

So, whatever stock you buy to do the job you'd be best to sticker it up in conditions that will bring it to about this MC. A covered but open shed would be ideal for this at this time of year. 1" thick stuf, for example, will rise from 8% MC to about 14% MC in about two to three weeks. Stuff that's at about 20- 22% MC will take about 6 to 10 weeks to get down to about 17% in current RH conditions in this country, ie, about 80%- 85% RH. Wood gains moisture quicker than it loses it due to the effects of hysteresis.

For stability try and use 1/4 sawn wood for rails, stiles, intermediate rails, etc, even though radially cut material is more expensive. It's more stable than tangentially cut wood and should add stability to the whole door structure. Slainte.

 

[opener]

Thanks a lot for your learned response Sgian. I now feel much more confident of my approach to this job.
Cheers
Malcolm

 

[Digit]

Out of curiosity, how many of you place the lower fame on the inside only of the door, as I do, and how many do a full frame. I find that with T&G a full frame soon results in rot where the water runs down the T&G and rots the lower frame, but with the T&G running down past the lower frame the water simply runs away.
Comments?

Roy.