Hearth Clearances

Planning out flooring etc for lounge at the moment. Plan is to fit a multifuel stove (firefox5)

I've seen 2 different diagrams regarding the clearances the hearth must be from the builders opening, one saying 500mm from a jamb and the other 300/225 from the front of the appliance.

There currently is a very thick slate hearth in place but will be laying a few slabs down on top and tiling over them to get the look and size we need. But not sure what that is going by the diagrams 500 from jam or 300 from appliance?

also a solid fuel burning stove, is it considered a closed appliance or open with reference to the 300/225mm measurement?

Normally you would go with the stove manufacturer's guides as they take precedence. The Building Regualtions are really just a guide and a slight difference of dimensions is not that important.

Diagram 24 is the constructional heath - the one in the floor, and it looks like you have something that is OK. This is really just to protect the floor joists from heat.

Diagram 26 is the working heath and can be smaller and is to protect the floor coverings. The idea of the 225 and 300mm dimension is to protect against sparks and embers jumping off the fire. If the stove will be used with open doors, then its the 300mm, if closed doors the 225mm.

Having spent time just reading the regs again and again, as I found it confusing at first...it's important that the constructional hearth shown in your pic is sound and completely non combustible to depths shown in Sec J and it extends MIN 150mm both sides of your jamb and projects MIN 500mm. I cant tell from the pic, If your constructional hearth is sound and dimensions ok, then your 'decorative' hearth can sit on top and looking at your pic its logical to make the right hand side wider than the constructional hearth to match the left.

It is surprising how many people, including Stove companies, have misunderstood regs, particularly in regards to stoves generating less than 100 degrees at the hearth. Some state in this case the stove can be fitted in an 'inglenook' or fireplace recess without the need for a constructional hearth as a 12mm decorative hearth is adequate. This is not correct. The 100 degrees min 12mm decorative hearth option only applies if the stove is FREE STANDING. (And yes, To me this doesn't make logical sense, but the regs are there for a reason).

Also, re the 250mm or 300mm depth from stove door...it would be wise to keep at the 300mm either way as I'm informed people often leave the stove door open sometimes.

Hope this helps.

I wasn't completely clear was I. In answer to your specific question, you need to comply with both. The constructional hearth min projection 500 and then your decorative hearth either 225mm or 300mm. I suggest you stick with the 300mm also for reasons stated previously. As a note, my friend has a woodburning stove and the decorative hearth is 325mm deep. She also has a burn mark in her carpet in front of the hearth. Fires, sparks and spitting embers don't always comply with Building Regs! Building Regs are normally shown as MINIMUM requirements, which is not the same thing as best practise.