Advice on putting in lintels please

[VWBrian]

Hello, I've started a little project opening up an external ground floor wall to put a window in and would really appreciate advice on a few questions. I’ve researched but too much info and no real answers has left me confused.

The house is 1930s so got them dense heavy bricks, it's a cavity wall so need to open up both skins. There are no 90 degree walls coming off above on the floor above and the floor joists run parallel with the wall so no load to worry about there either. So I’ve only got wall above my opening all the way up to the roof, oh and the highest point of the roofs apex sits at the top of the same wall so roof joists are not giving load either.

The opening I'm making is 850mm wide and I'm using a 1200mm prestressed reinforced concrete lintel from b&q which gives me the suggested 150mm end bearings.

Now the questions.

1. Will a strongboy deal with both skins from one side of the job or would acrow props be better, and considering the width of the gap I’m making how many of either would I need considering what sits above?


2. Once the lintel is up flush to the top row of bricks it will leave a 40mm gap beneath it and the end bearings. Should I dry pack the gap and smack some 100mm x150mm slate packers in, or steel packers? and if so what is the correct process/order for doing it?



3. Is it best to run a layer if dry pack along the top of the lintel before I offer it up to the bricks and if so how thick considering the gap between the lintel and the bearing ends?



4. How long should I leave everything to go off before removing the props?


5. Do I need to get Building Regs to come and approve it ?


I think that’s all, any advice, guidance or suggestions would be very much appreciated, thanks

 

[23vc]

I’d just take the bricks out and put the lintel in and pack it. Wouldn’t bother propping for that length

 

[noseall]

1. Will a strongboy deal with both skins from one side of the job or would acrow props be better, and considering the width of the gap I’m making how many of either would I need considering what sits above?

Strongboys are attached to Acrow props. You will need 1 each side smack in the middle plus another two for fiddling...

2. Once the lintel is up flush to the top row of bricks it will leave a 40mm gap beneath it and the end bearings. Should I dry pack the gap and smack some 100mm x150mm slate packers in, or steel packers? and if so what is the correct process/order for doing it?

Apply wet - ish mortar to the top of the lintel, press it into place with your two fiddling Acrows then slip some packers* under the lintel bearings. You may need mortar with the packers depending how they seat.
*Packers = thin slab, slate, artificial slate, tile etc.

3. Is it best to run a layer if dry pack along the top of the lintel before I offer it up to the bricks and if so how thick considering the gap between the lintel and the bearing ends?

Read above.

4. How long should I leave everything to go off before removing the props?

Next day.

5. Do I need to get Building Regs to come and approve it ?

Not necessarily no.


How are you going to deal with both skins with only one lintel?​

​

 

[VWBrian]

Thanks Noseall, I have two lintels
When I asked about acrow props instead of strongboys I meant with timber though a hole knocked out above.
I've read a lot about dry packing , 3:1 mix with sharpsand, why would you use wet ish mortar?

 

[^woody^]

If the bricks are tight and the mortar relatively soft, you can cut them out gently with a hand saw and no propping.

If you dry pack, then there is no waiting period if you do use props.

You need a cavity tray.

Strictly the work requires b/regs approval. If you are not moving any time soon, then its up to you if you want to bother or not.

 

[noseall]

Strictly the work requires b/regs approval.

I've never seen them bother with door sized openings unless there was an amount of engineering or loading involved?

Just read the OP properly (oops) - would it be the window etc?

 

[noseall]

I've read a lot about dry packing , 3:1 mix with sharpsand, why would you use wet ish mortar?

It just knits better and you can monitor the amount of squeeze you impart with the Acrows until the lintel is bob-on level. And it loads easier to work with than dry mix poo.

We do have the benefit of having more than a dozen (owned) Acrows lying about though.

 

[cdbe]

You need a steel catnic type lintel for face brickwork - those concrete ones have a rough finish and would look terrible. You'll need to take 2 or 3 courses off above then sit it (with a thin mortar bed) onto the brick either side and rebuild the brickwork above it (with some weep vents).