Help designing double doors for a shed

My opening is 1835 high and 1365 wide - there is a little variance in the width, I think mainly caused by the trim warping slightly on one side so it's actually 1365 wide in the middle, but at the top and bottom is 1368 so 3mm difference.

I plan to build the doors out of 4x2 CLS covered with 14mm thick T&G making the doors 52mm thick.

2 verticals stopping 11mm short of the floor to make fitting them easy as I'll simply rest them on a piece of 11mm plywood, 3 cross pieces located where the hinges will go and 2 diagonals for support make up the frame. The T&G will extend down at the bottom covering not only the 11mm gap, but also a little further to stop rain blowing underneath the door onto the floor.

Regarding the door overlap, I'm thinking of cutting a rebate in the frame of 10mm in the LH door and obviously 28mm out of the back of the RH door so that where the doors meet, the LH door will be 28mm of CLS and the RH door will be 10mm frame + 14mm T&G - not sure how much overlap to have here - I guess it depends on my next question.

What I don't know is what allowances/clearances I should leave? I read for internal doors around 2mm, but I guess that doesn't apply to an exterior door where things are likely to move about a bit so is 5mm enough either side and 10mm in the centre?

Anything else I've missed?

 

I would leave 10mm at the side to allow for expansion and clearance when the door opens, and less in the middle.

Wood does expand with winter moisture so fitting it now might allow for tighter tolerances.

This Robin Clevett video might help:

How To fit Garage doors - YouTube

Blup

 

It's all kiln dried stuff though I'm using so unless I left it out for a few days before fitting I guess it can only expand.
I'll be treating it all before assembly and then painting it.

Here's a though though - the T&G - do I need to allow room for THAT to expand as well, i.e. allow a small gap between the joints? I was planning to glue them, but rethinking I guess that's a bad idea right?

 

That's a cracking video btw - I was wondering what to use for a lock and the tips on using the screw positions to fight movement in the hinges is brilliant.

He doesn't allow much expansion though? Just 3mm on the sides.

 

I found the t&g boards I used to replace rotted boards on my own garage doors fitted snugly without the need for glue, and allow for a degree of movement as such. There have been no problems since doing it a few years ago.

Blup

 

I would not frame the doors but use 4x1 or 5x1 ledger and brace which would reduce chances of movement overall.This would also reduce the overall weight and allow T hinges to be used.
Also good if you can provide shelter above the doors to minimise weather effects on the doors.

 

The doors are sheltered with both a roof overhang, and cladding overhang - although water will inevitably hit the surface of the door, no chance of it getting behind (hence I'm comfortable using untreated wood for the frame).

I prefer the 4x2 approach - weight is not an issue - the hinges chosen are capable of supporting a much heavier door - but key with 4x2, the screws for the hinges actually have somewhere to go - I can put 50mm screws in and not have them sticking out the back. And frame is essential for the overlap.

I'll treat and coat the tongues and grooves before assembly and install with a 1mm spacer between each board to allow for expansion.

 

CLS bends all over the place once it's outside and stays getting exposed.

For many years I've used deck boards for many shed doors, dates and out houses, mortice and tenon the joints and they are solid and don't bow. The infill can then be t&g or suchlike.

 

I would leave 2mm for expansion between t@g - I used to make t and g doors in oak and hardwoods, being kiln dried down to 12% they needed 2 or 3 mm.

Softwood t and g is probably kind dried 12% or higher or could be shipping dry 16% to 18%

Don't rebate the doors - That's a precision detail for internal doors. Use cover strips maybe out of the 14mm t and g ripped down to 60mm and chamfers on long edges.

If you want the doors to last a long time, put a 3 or 4 mm radius on the bottoms and all external edges - it allows the surface coating to maintain film thickness at the edges.

Set bottom ledge up by say 150 mm and top one down by say 100 mm so hinges are visually in right position....it looks horrible when hinges are right at the bottom

 

Yes - my plan was to align the ledges with the preferred hinge locations - I'm going to have a crack at mortice and tenoning them - last one I did was in school so I'm currently building a jig from a YT video and going to have a crack at some scraps to see if I can get them good.

What's the problem with a rebate like with the garage doors in the video linked above? The doors will be fully painted before installation.

Good tip about the radius - is the factory rounding on the CLS sufficient so I just need to rout the edges I've cut?

 

Yes rounding on CLS is fine.

Actually what you could do with the rebates outside is allow one T&G board to stick over by say 25mm and leave the other side shy.

I wouldn't do rebates because your doors will shrink and expand.....and are pretty likely to twist.

A cover strip hides all that, a rebate doesn't and it looks untidy once the doors twist.


Mortise and tenon - good idea if you fancy having a go.

A half inch tenon is fine.

Make the tenon about half a mms small....if you make it tight you will struggle to get together.....and if you have no sash clamps you got no chance unless on the loose side

If you are doing a through tenon, put a slight splay of 2-3mm on the outside edge of the stiles so you can bang wedges in

Only do shallow mortises on middle ones - deep or through tenons on midrails weakens stiles and encourages bowing.

Through mortises on top and bottoms is the strongest -and good because you can drill from both sides.

Mark out your door components with face and edge marks. When you square around the shoulders put the square only on a face or edge....that way the lines will meet all way around.

choose your stiles from the flattest boards, cut to avoid knots at the mortise positions.

 

Wow! Thank you so much for taking the time to write all that!

Using a T&G only for the overlap was my original intent, but someone else advised me to use rebates as the T&G is only 14mm thick - but I guess if I install door stops (is that the right name?) then that wouldn't matter as they'd stop a slamming door, not the overlap. I was thinking that a rebate with the M/T joints would complicate things so I'll revert back to that plan. Will the timber absorb moisture even if it's sealed (painted)? I chose untreated CLS being careful to pick straight pieces because the treated stuff was all over the place and I figured I'd build the doors inside and paint them before fitting to shed to stop movement - I'm guessing it doesn't work that way?

I do have a couple of sash clamps.

Half inch thick and the other dimension? 2 1/2 inches, allowing 1/2 inch either side?

I don't understand what you mean by "when you square around the shoulders put the square only on a face or edge"?

Really good tip about avoiding knots, I'd never have thought about that until too late.

One last question - for the braces I was planning on using the style in this guide, i.e. tight to both the rails and stiles at each end as opposed to those on many retail doors that are simply joined to the rails. Note I'm not following this guide as I won't be rebating the T&G - as you mentioned in your previous post, better to set the top rail down a bit for the hinge.