Knock through door?

[garry1234]

Hi all,

I know this seems a daft question BUT here goes!!

I am knocking through an internal wall & installing a lintel. The door I would like to fit is 760mm or 30 inches. How wide should I am for making the opening bearing in mind I need to fit a door casing etc. Do I just open up about, should I make it 33 inches or wider or less?

Please could someone clarify.

Thanks in advance.

Gaz

 

[noseall]

when we do a knock through for a standard 762mm internal door and casing we make the brick-to-brick opening 910mm wide, and install a 1200mm lintel.

this extra wide opening allows us to fix two lengths of 100x50mm timber up each side. you can then fix the casing to the carcassing timber, and have the freedom to put the fixings where you like.

it can be tricky sometimes fixing a casing directly to shattered bricks, though i must say expanding foam does make the job a little less difficult.

 

[garry1234]

Thanks very much for your quick reply. I was told to use pre stressed 2.m concrete lintels & I note you use 1.2, any particular reason or is 2.1 lintel OTT? I've also been told to get 2, do they go side by side?

Thanks again.

Gaz

 

[^woody^]

A 2m (2.1) lintel would be OK for patio doors, but otherwise nore than twice as long as you need.

Why don't you just buy the casing, knock it up, put it on the wall, mark around it plus 10mm and then cut the opening?

That's a good idea with the timber up the sides. Once I have used up this last box load of expanding foam, I may start doing that. I wil probably need to start buying some fixings though. lol

 

[garry1234]

A 2m (2.1) lintel would be OK for patio doors, but otherwise nore than twice as long as you need.

Why don't you just buy the casing, knock it up, put it on the wall, mark around it plus 10mm and then cut the opening?

That's a good idea with the timber up the sides. Once I have used up this last box load of expanding foam, I may start doing that. I wil probably need to start buying some fixings though. lol

I like that idea even better. Do you know why I've been told to get 2 Lintels????

Gaz

 

[noseall]

Do you know why I've been told to get 2 Lintels????

Gaz

if the wall in question was previously an external wall then you will most likely have two leaves of masonry to deal with.

 

[^woody^]

You only need two lintels if the wall is the same width as two lintels - ie two side-by-side.

If it is an internal partition, about 100mm wide, then you only need one.

 

[garry1234]

You only need two lintels if the wall is the same width as two lintels - ie two side-by-side.

If it is an internal partition, about 100mm wide, then you only need one.

Okay. thanks Woody!

Gaz

 

[garry1234]

Question? Which door casing would I need?

Rebated Softwood Door Casing
Size: 33 x 131mm

Rebated Softwood Door Casing
Size: 33 x 106mm

the door I'm fitting is a standard 762mm

I don't understand how the caings work out??

Thanks in advance again!!

Gaz

 

[noseall]

there are generally three widths of door casing.

the widest 147mm is used on 100mm masonry walls that will be dot 'n' dabbed.

the next size down is 133mm for use with 100mm masonry or studs.

the smallest, 108mm is for use with 75mm wall thickness.

 

[diyisfree]

I knew i had a few piccies about somewhere maybe these will help you. 1200 lintels were used here

Here you go,

You can see the lintel in place here and also varying stages. This is what is meant by lintels side by side as this was an opening i created into the exterior wall and into the new extension. A lintel is required for the interior, and old exterior brickwork. Note the casing is made from ply because of the twin leaf and cavity bridging.

If you look closely to the right of this picture you can see that only the exterior wall is broken through and again the lintel is in place. I cut from the extension into the house in order to keep the dust to a min.

Anyway, hope they help you.

 

[garry1234]

That is excellent, thanks very much diyisfree!

Gaz

 

[Gerrydelasel]

it can be tricky sometimes fixing a casing directly to shattered bricks, though i must say expanding foam does make the job a little less difficult.

How does this work? Do you hold the jamb approximately in place and squirt some foam behind it, or something?

 

[^woody^]

Do you hold the jamb approximately in place

Yes that's it.

But if you dont have the time or steady hands, you can always wedge it instead

 

[noseall]

How does this work? Do you hold the jamb approximately in place and squirt some foam behind it, or something?

Not quite.
Setting up a door casing is tricky with the various levelling parameters and plaster protrusion amounts etc.

The casing needs to be plumb (upright) in two planes.

It needs the head to be level (even if the floor isn't).

You need to have equal amounts of protruding casing in order to deal with plaster thickness. This can have added tricky-ness if the wall you are fixing to is not upright or that you have a light switch boxes to contend with on both sides of the wall.

We always plug and screw (or just screw into wood) then use foam as a back-up. Another way of getting a good fixing backing (in a brick knock-through) is to remove a large enough opening so that you can dab a board up each jamb before offering the casing in place. Once this is set you end up with a nice plumb surface to fix directly to. Always set it up so that you fix the casing flush with the hinge side and do all your packing from the latch side.

Always mark off where your full bricks are before covering them with dab and plasterboard. Helps with the plug and screw. Screwing into shattered half enders is no fun.