How to Support Consructional Hearth for Log Burner in a wooden floor

[Jake Howlett]

Hi,

I'm trying to make sense of this image from "Document J". It makes sense, but what I can't figure out is whether this hearth is just supported like a cantilever? Is it the case that no combustible material (my floor joists) can come within 50mm of it?

I've seen the version below where somebody has added to the image to show how it could be supported by the joists of the floor. This makes sense and answers my question above, but it's not from an official source, so I'm reluctant to take it at face value.

 

[blup]

I think a sleeper wall (or something similar) would support the end of the hearth, the pictures are purely to illustrate the principles of the regs.

A cantilever is an engineering possibility but would be unnecessary overkill.

BC would have to approve it anyway.

Blup

 

[Jake Howlett]

I think a sleeper wall (or something similar) would support the end of the hearth, the pictures are purely to illustrate the principles of the regs.

A cantilever is an engineering possibility but would be unnecessary overkill.

BC would have to approve it anyway.

Blup

I'm not sure what a sleeper wall is (I'm just a competent DIYer). To be clear it's the edge of the hearth on the right of the image that I am talking about. In the image it's just hanging freely. When I talked about it being cantilevered I just meant that it would stay in position in the situation shown in the diagram as it appear to extended in to the brickwork of the wall.

 

[Jake Howlett]

I think a sleeper wall (or something similar) would support the end of the hearth, the pictures are purely to illustrate the principles of the regs.
Blup

I Googled sleeper wall and see what you mean now. This isn't an option as the fireplace is above our cellar (and directly above where the main electric cable comes in to the house).

 

[blup]

There must be quite a combined fire risk from all of that - you might find it helpful to take advice from your local building control officer, or a HETAS qualified fitter.

Blup

 

[Jake Howlett]

Thanks Blup. I'll do as you suggest and seek professional advice.

 

[blup]

Constructional hearths are present in first floor rooms, and they basically rest on floor joists.

However the cellar ceiling construction would have to be pretty robust to support the weight involved in a compliant hearth for your design.

Building control are a good - and potentially cheap - source of initial advice.

Blup