Lintel?

[Jackuzi]

Hi all,

I am planning to cut a hole in an internal load bearing wall to pass a new 8 inch (external) twin wall chimney flue through. I am passing this through on a 45 degree angle (both vertical and horizontal) and this is below a joist that has a small masonry wall above. I am thinking I might need to insert a new lintel at the top of the ground floor wall, below the joist to spread the load over the hole below but I'm not sure what needs doing?

The top of the hole will start roughly 280mm below the ceiling, cross under the joist and come out the other side roughly 80mm below the ceiling.

Am I right about putting in the lintel or is the another way/not needed? I have added a couple of drawings to hopefully explain it in picture form.

If none of the above is clear please tell me and I'll try to explain myself better.

Thanks

 

[Jackuzi]

Can anyone help on this please or point me in the direction of who I might ask?

 

[jeds]

Your drawing is slightly confusing but you wouldn't generally need a lintel for structural reasons but it can sometimes be easier to have some sort of retaining lintel (something like a flat plate) for practical reasons.

 

[Jackuzi]

The second drawing shows the top down view of the route of the pipe from the wood burner in black pen. The other pipe route drawn in pencil is an alternative route but adds another offset which I'm trying to avoid.

I'm not sure what you mean by a retaining lintel?

 

[themiddleagedun]

I would cut out an appropriately sized hole for the flue to pass through and use a short 100x65 concrete lintel to span the opening, allowing 100mm bearing on each side.

To cover the hole you could use a piece of supalux fireboard cut around the flue, glue/screw it to the wall and plaster up to it.

 

[jeds]

The size and angle you describe makes it very difficult to cut a clean hole. So you will have a certain amount of making good around the flue. Not so bad under the flue and not so bad to the sides but it will be quite difficult to make good above without basically laying bits of brick or something directly on the flue. So whilst you don't need a lintel for structural reasons you will probably find it easier to just make a bigger hole with a light duty flat plate lintel over - something like a meter box lintel or just a 4mm flat galvanised plate - and then make good around.

 

[Jackuzi]

Thanks guys

 

[Jackuzi]

I if go with putting in a 600 x 100 x 65 steel reinforced concrete lintel over the cut, can I cut the hole for the lintel first, get that in place then go ahead with cutting through for the flue under that?

Can I disc cut the hole for the lintel to the same dimensions and then squeeze the lintel in?

Do I need to take the load on an acrow before cutting for the lintel?

Thanks

 

[themiddleagedun]

Cut everything out at the same time.

I would say you'd only need to remove 3 bricks to get the lintel in, so no need for an acrow, and something like a 300x300 hole for the flue.