Help/advice on outward opening door frame

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11 Dec 2017
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Hi all,

I have been following this forum for many years. I am nearing the end of building a small workshop/office and I would like your advice on the door frames I am hoping to get started on in the next few weeks. It's been a long build (started at the beginning of covid lock down). Time, money, work, family, a lot of procrastination/research and questioning my abilities - I'm a plumber by trade so please go easy on me.

There will be two doors and frames, both outward opening (to maximise space in the workshop and the office door, just to match).
I have 6 x 2 redwood timber for the frame, 2 x exterior grade fire door blanks and hardwood lipping, and a bunch of mahogany type door frames I would like to use for cills. I know there are better materials that could be used but this is what I have.

I have possibly a million questions I could ask but it would take me forever to write them, so hopefully with some pictures it would make more sense, and you could let me know if you can see anything wrong with what I have in mind.

With a 44mm door would a rebate width 47/48mm be about right to account for the Aquamac seal? Also, depth of the rebate - 15/20mm?

I have rough cut the heads of the frames over sized. Would a straight mortise and tenon suffice or haunched M+T. If so, would the haunch be on the external corner of the joint? Horns would then be cut flush with the verticals.
The mahogany type frames would be too short to stick out beyond the cladding and reach back to the flooring, so I would need to add a piece to the back. There is a fire strip groove already in the frame I could use as the drip edge of the cill. I plan to M+T the frame to the cill. I also have some mahogany or sapele 1" x 1" I could route a chanel into the cill + weather seal for the bottom of the door.
How far beyond the cladding would be best for the cill to sit?
I will need to sand the paint off the cills.
This is the wife's office side of the build. 6x2 door frame boards rough cut over sized. The skirting and architrave is for in the house. The wife has also started and roped me into doing MDF panelling in the livingroom and new window boards.

Sorry for the many questions for a 1st post.

I know I'm making life hard for myself for what I'm looking to do, but I also see it as a good learning curve and to push myself out of my comfort zone.

Thanks all in advance



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There’s quite a few points raised here, it’s a bit tricky to address them all, so apologies if I don’t cover everything

1) aquamac seal - it depends on the seal, it could be anything from 4mm to 7mm and rather depends on whether it’s acting as a compression or wiping seal.

In general your dwg is a bit wrong as a seal in that position would normally be sized to match rebate depth so the seal is flush with the frame when door closed

2) cill projection needs to be far enough for drip groove to clear, typically in brickwork a 90mm frame might have a 160mm cill, giving a 70mm projection, so frame set back 25mm would give a 50mm cill projection.

I would make the cill so the slope goes back to the rebate in the frame then scribe jambs with same angle (chop saw can do it)

Frame mortices are positioned adjacent to the rebate and are full width of jamb - no haunch.

Don’t forget cill needs 50mm horns each end.
Quick sketch of better options for seals using Aquamac AQ21, either is fine or both for belt and braces.


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