Superimposed hearth overlapping wood floorboards

[JKScotland]

Hi folks, I'm in the process of preparing a superimposed hearth and would like a little advice. I'll be tiling it with porcelain tiles but want it raised above floor height - e.g. 50-70 mm - something like the first photo below.

Untitled

• JKScotland
• 21 Jan 2014
• 1

The superimposed hearth will extend a little past the constructional hearth and overlap the suspended wooden floorboards - see second image...

Untitled

• JKScotland
• 21 Jan 2014
• 1

I have 2 questions
(1) What material should I use to build up the 50mm? (B&Q chap suggests screed of some sort, like a floor-leveling compound.)
(2) I plan tp put down some sort of sheeting (DPM) in a temporary timber frame to contain the poured screed, otherwise it would run down in between the floor boards. Does that sound like a sensible way to approach it?

 

[conny]

Is the constructional hearth flush with the top of the floor boards at present?

Is the new hearth going to lie on top of this?

How far past the original will the new hearth extend?

If it is only extending over the floor boards by an inch or two, (25-50mm), then I would think there would be no problem regarding load bearing. However, you may have a problem at some time in the future if you need to raise the floorboards. The chances are that there is a trimmer joist running across the front of the present hearth and the ends of the floor boards will be secured to this. One way to over come this may be to trim your boards back to the next joist so if you have to lift them at some future date you will not damage the new hearth. This is assuming of course that your floorboards run to the fire place and not across it. If they run across then there should be no problem.
For the new base I would construct a frame as you have suggested and line it with a plastic liner. I would also use concrete rather than a levelling compound.

As I am not a builder please seek advice from a professional before taking my word for it. With luck someone else will respond to this post and point out any errors I may have made.

 

[JKScotland]

Conny, thanks a lot for the reply.

Is the constructional hearth flush with the top of the floor boards at present?

Slightly lower (5mm if that)

Is the new hearth going to lie on top of this?

Yes it will

How far past the original will the new hearth extend?

I think it's only going to be 50mm at the front and maybe 100 at either side. Something like that.

I would also use concrete rather than a levelling compound.

I know very little about concrete or the levelling compound - can you tell me why? Cheaper I would guess. Does it set quicker too? Any ideas on what kind of sand to use and ratios? I don't really know where to start with that.