Door aperture width in a masonry wall, a tad urgent.

[epsilonGreedy]

I am laying some footing blocks that will stand about 20mm proud of the FFL of my garage floor ground bearing concrete slab. There is an internal door in this garage/workshop.

 

What door aperture width should I create in the masonry wall to accommodate a future door frame kit for a 30" door?

Edited January 8, 2020 by epsilonGreedy

[AliG]

The internet suggests that you add 2 inches to the width. BTW that is narrow for a workshop door.

 

[epsilonGreedy]

5 minutes ago, AliG said:

The internet suggests that you add 2 inches to the width. BTW that is narrow for a workshop door.

 

 

I think you are right about the width, I just picked 30" as an example.

 

The "workshop" portion of the garage in this particular side of the garage is really more of an internal store shed about 9' x 7', the largest item in there will be  lawn mower. The internal store might become a sauna at a later date, so perhaps I should expand the question to sauna door widths.

[Jeremy Harris]

I agree, a 760mm door is going to be a bit on the tight side.  I made the side door on my workshop the same width as all the doors in the house, and they are all 838mm.

 

To answer the question, I've just checked and our internal door linings are all 30mm thick, so allowing for two of those, plus a working clearance for the door, plus enough width to pack the lining true, I'd say that the rough gap needs to be around 70 to 75mm wider than whatever size door you go for.  You can get slimmer linings though.  I believe some may be around 25mm to 28mm thick, which might knock a few mm off the rough gap needed.

[willbish]

I found this helpful when looking up structural opening sizes.

 

Opening-Dims.pdf

[Declan52]

Leave the opening 910mm for a workshop door. 

[Mr Punter]

I would go for a 926 door if you have room.  I would make the opening 1000.  If you have check reveals on 2 skin make the outer leaf 980.

[epsilonGreedy]

On 28/05/2019 at 19:28, Mr Punter said:

... If you have check reveals on 2 skin...

 

 

In case anyone else is also wondering what a check reveal is.

 

https://www.illbruck.com/en_GB/solutions/window-installation/check-reveal/

Quote

A ‘check reveal’ is a detail that is particularly common in Scotland and Central Europe and involves an opening being formed in the external masonry skin where the external structural opening is smaller than the window frame and consequently the external face of the window frame when installed butts up against the back of the external skin. In this scenario the primary weather seal is formed between the front face of the window and the opening rather than the outer perimeter of the window and a conventional ‘flush’ reveal. The check reveal undoubtedly therefore produces a more protected joint and 

 

[Brickie]

On 28/05/2019 at 18:16, epsilonGreedy said:

 

I am laying some footing blocks that will stand about 20mm proud of the FFL of my garage floor ground baring concrete slab

 

Are you asking so you can cut the blocks down where the opening is? 

20mm upstand would achieve some very nasty nicknames from one as clumsy footed as me. 

[carlb40]

External door frames off the shelf are usually 45mm thick. So you would allow 45mm - frame  + 3mm gap + door width + 3mm gap + 45mm frame, plus 5 -10mm either side for packing / plumbing the frame up. 

So taking your 30  inch  ( 762mm) door as an example your opening would be 878mm which includes 10mm gap either side of the frame.  

Edited December 17, 2019 by carlb40