Building Regulations: Approved Document J & Hearths

[TheJay]

Hello there, I am completing the paperwork for my installation of a 3kw multifuel stove. The constructional heath consisted of concrete at least 25mm thick above the subfloor (no idea how thick that is) and topped with a granite hearth, which is again 25mm thick.

This leads me to the following question:

Hearth, form of construction. New or existing?

Examples:
New. Tiles on concrete
floor. 125mm thick. As Diagram 25 AD J

Existing hearth for solid fuel fire, with fender.

New. Solid floor
Min 125mm concrete above DPM. As Diagram 42, ADJ
​

Can someone please tell me which diagram I should be referring to in relation to my installation? I can't even see a diagram 42 in the document mentioned.

Someone from building regulations visited today and approved the slab, I just need to complete this paperwork to get it signed off.

Thanks for your help.

 

[oldbutnotdead]

Page 62 for Diag 42, Page 37 for Diag 25 (both references in the Online version)

 

[^woody^]

Why do you need to fill any of this in paperwork, if the inspector has inspected?

 

[TheJay]

Good question, I don't know. When he looked at it, he said it was fine but to complete the document and email it across to their office?

 

[^woody^]

What document? I dont recall any that ask for this level of information.

 

[TheJay]

He was referring to the checklist in Appendix A in Approved Document J. In any case, I need to know the answer for the data plate, which asks the same questions.

 

[^woody^]

That form is for a different purpose. It should be for you to certify anything if you have paid for the council to inspect and certify it. I've never known the inspector to ask for this info.

 

[TheJay]

That may be the case, but I do need help figuring out exactly what to write for that section.

 

[TheJay]

Anyone?

 

[Leofric]

' The constructional heath consisted of concrete at least 25mm thick above the subfloor (no idea how thick that is) ' - is that a typing error ,you can't lay concrete 25mm thick Might be missing something but how does anybody know the construction of your hearth if you don't ?

 

[TheJay]

I meant that the thickness of the subfloor is unknown. I expect it is at least 12 inches because I had to dig out some of it in another room downstairs to get to the mains water pipe.

It's hard to remember exactly as the project has extended over a number of years.

 

[Leofric]

Don't know if anybody else can help but I am confused