Door frame thickness?

[RobTro]

G'day all. Need your wisdom,

I will be making some doors for my shed. timber Frame sandwiched between ply or OSB sheets (to stop sagging) and hardwood T&G planks (siding) on the exterior. Very heavy.
About 1900mm high and 880mm wide each door. (two doors)

Questions.

1. the interior frame construction of the door - should be what thickness? I was thinking of 4x2 Spruce or similar dimensions in some other softwood? Comments? I figure that to hang the door I would need about a 4x2's thickness being 38mm minus a mm or so needed to straighten things out. But I can look for thicker wood if you recommend. (I am in Japan so maybe not eveything is available) What do you need for fitting most hinges. What is the standard length of screws for heavy duty hinges?
2. The door frame (or JAM?) - What thickness is normal? I am planing on using hardwood for the door frame. I was thinking of 30mm.(getting expensive) Or could this be reduced to say 24mm or 25mm and just plan on using extra long screws to fix the hinges through the door frame into the studs around the door.? What is normal for a heavy door and what is the normal installation method?

Thanks for any help,

Rob

[billbeee]

Hi Rob,
Just behind me as I type this in my shed are a pair of solid core doors, 900 x 2040 x 42 thick. Fairly heavy. Fixed to a softwood 110 x 32 door jamb. Swung on thick 100mm butt hinges, 3 per door. Fixed with 30mm long screws. Solid as, not moved in the last 8 years.
I have made and fixed similar sized doors out of two layers of 16mm MDF with a 1.2mm lead sheet in the middle for radiology rooms. These were very heavy. From memory I used same sized jambs screws and hinges to swing them. Only I used ball bearing hinges to handle the extra weight. (This type of hinge is used on aluminium and glass doors on shops etc. also very heavy).

I wouldn't use less than 32 thick timber for a door jamb. It is a hassle fixing and keeping straight ex 25 timber.

I'd probably use ex 75 x 35 ( 3 x 1 1/2) internal frames for the doors. 4 x 2 seems a bit overkill, but I don't know how heavy you external boards are going to be.

The strength of the doors will depend on your fixing of the ply or OSB to the frame.

Cheers
Bill

[RobTro]

Hi Bill, thanks for the info. The 4x2 internal frame members are just "4x2" spruce used for house construction. Actually they are 38mmx89mm. They are cheap. I'd say that by the time I planed off a bit to straighten them out they would end up at around about 75x35 as you suggested. I can check through the timber in the store and get the strightest ones but they nearly always have something that will need to done so they can be used for a frame.

What do reckon for the joints for the internal frame? Do they need to mortice and tennon or because the racking forces will be taken up by the ply sheeting, would a doweled or screwed lap joint be OK?

OK It sounds like the 30mm jambs should be the go. and the door will just habg off the jamb. So I need to secure the jamb to the frame. What spacing would you say for fixing the jamb to the frame?

Rob.

[billbeee]

Hi Rob,
The joints in internal frame for the door as you say are not all that critical, they are only there to hold it in position until the glue etc. holding the ply takes over. A lap joint would be excellent.
If you went to the trouble of making lap joints, I'd be tempted to put a couple of braces inside the frame and just sheet the inside with ply and fix you boards directly to the frame on the outside.
You mentioned mortise and tenon, if you wanted to make the job a definite project, you could make yourself a pair of frame and filled doors.

I would fix the jambs with a pair of screws in four spots, just over your top hinge, just under the bottom and two more sets equally spaced in between.

cheers
Bill