Widening Chimney breast space..lintel width

[HandsPlusBrain]

Hi. This is my first post. I am seeking advice on widening a chimney breast void but not for fire or anything like it.

I have uploaded a super rough diagram of what I want to do - with measurements:

Fireplace Diagram

• HandsPlusBrain
• 5 Jun 2013
• 1

Proposed widening of fireplace.

There is a blanked off old pipe on the right of the stack in alcove so where a gas fire clearly used to be connected (like it when we moved in). The void in the chimney is boxed/lined with thin ply and a skirting frame surrounds the face of the void (sounds like the book of Genesis).

I want to widen the existing void but lower the opening to make an oblong hole in the chimney. Would I be able to simply add a lintel underneath what's already there to achieve this? Would a 1200mm concrete lintel be sufficient/correct size for bearings? I am clueless quite frankly but nonetheless able.

The idea is that the new cavity will (I hope) house four home cinema and hi-fi components (2 components on each shelf) and a flat screen television will be mounted just above it (so tv mounted low at more or less eye level). So I will be feeding cables into the stack through holes in left and right sides. Thinking of using surface mounted brush boxes as cable access points.

Could anyone give me any advice on this project? Any guidance would be appreciated. I am now getting myself geared up to do it but I want to make sure that I'm not proposing anything that will bring the fireplace down. Is widening the space to 920mm feasible?

This will be a first time project like this. I'll be doing it all myself unless advised otherwise.

Thankyou

 

[saladdays]

The first thing to do is remove that plywood and some plasterwork to ascertain the structure. Is it 6.5 bricks wide? How thick's the plasterwork?

Both sides need double bricks, so the opening will be: total width (1520) minus two bricks lengths (216 x 2) equals 1088. Or you could have 330 wide brickwork on both sides which gives an opening of 860 (must be 3.5 bricks?)

The lintel length is opening (1090) plus two brick widths (102 x 2) equals 1294. Buy a concrete one and trim to length. You'll need a large angle grinder with a diamond blade.

Lintel bearings are 100mm if the gap is less than 1000mm, otherwise it's 150mm.

Draw a picture showing where all the bricks and lintels are / will be and it will all make sense.

Also consider hidden lintels going back to front. Look at this: //www.diynot.com/forums/viewtopic.php?t=198129