Distance to Combustibles

[benben5555]

We are fitting a stove with a 200mm distance to combustibles at the rear. It's a timber framed house and the room in question is not plastered yet. The wall currently has 50mm PIR over the studs then an air membrane and 25mm timber battens on top.

 

The fitter came out and was concerned about the heat from the stove melting the air membrane so suggested a twin wall metal heat shield. This is expensive and requires ventilation at the top and bottom which doesn't really work as we are planning a fake chimney breast with alcove units either side. Also I don't really want to move the stove too far forward from an aesthetic point of view. 

 

Are there any alternatives? Like some kind of insulation board? I could remove the 25mm battens. Then my only concern would be the distance to the main studs in the wall and not melting the air membrane.

 

Thanks

[ProDave]

If the stove is 200mm from the finished wall, then the wall covering e.g plasterboard will be all you need.  you only need this heat shield if your finished wall is less than 200mm.  Is it?

[JohnMo]

First down load the install manual for your chosen stove, this trumps everything in building regs.

14 minutes ago, benben5555 said:

50mm PIR over the studs then an air membrane and 25mm timber battens on top

These are all classed as combustible.

 

You could change the construction locally to the stove.  Use an aluminium based membrane or a cement board, steel studs and Rockwool insulation.

 

Our planners insisted we used metal studs forming our service cavity in wall behind the stove. But became a needless upgrade, when I read our stove instructions. We have a Heat a Scanline and distance as trea to combustibles is only 150mm. As we were well away from combustion clearance required.

 

Different stoves have different distances to combustibles.

[nod]

Most installers flag plasterboard as combustible (Paper) I tend to use a cement board Skim or tile 

[ProDave]

29 minutes ago, nod said:

Most installers flag plasterboard as combustible (Paper) I tend to use a cement board Skim or tile 

But if your stove (mine) says 100mm to combustibles then plasterboard 140mm away is fine for example.

 

Still waiting for @benben5555 to say if his wall is greater than his "distance to combustibles" away from the stove or not.  THAT answer will determine how he needs the construct the wall.

[nod]

11 minutes ago, ProDave said:

But if your stove (mine) says 100mm to combustibles then plasterboard 140mm away is fine for example.

 

Still waiting for @benben5555 to say if his wall is greater than his "distance to combustibles" away from the stove or not.  THAT answer will determine how he needs the construct the wall.

[JohnMo]

23 minutes ago, nod said:

AI may say that, but it depends on the manufacturers instructions for distance to combustibles.

 

Mine for example clearly states 125mm at back and 350mm at the sides 

[Oz07]

Do you guys have photos of yours in? How do you maintain air tightness where flue passes thru wall?

[benben5555]

2 hours ago, ProDave said:

If the stove is 200mm from the finished wall, then the wall covering e.g plasterboard will be all you need.  you only need this heat shield if your finished wall is less than 200mm.  Is it?

When the stove is fitted I'd like to have it closer than 200mm to the surface of the wall yes

[ProDave]

8 minutes ago, benben5555 said:

When the stove is fitted I'd like to have it closer than 200mm to the surface of the wall yes

Then EVERYTHING less than 200mm from the stove must be non combustible, hence the ventilated twin wall steel panels suggested.

 

Have you bought the stove yet?  If not choose a different one, mine only requires 100mm to combustibles at the rear.

[JohnMo]

1 hour ago, Oz07 said:

Do you guys have photos of yours in? How do you maintain air tightness where flue passes thru wall?

Mine went through cathedral ceiling and I used something like this taped to airtight membrane.

 

[nod]

2 hours ago, JohnMo said:

AI may say that, but it depends on the manufacturers instructions for distance to combustibles.

 

Mine for example clearly states 125mm at back and 350mm at the sides 

It’s no great shakes to use a cement board rather than PB 

Most of the ones I do are tiled or skimmed Your only talking Pennie’s to use a cement board 

Ive put an oak beam on ours Your not supposed to do that either Done after installation 

[nod]

1 hour ago, Oz07 said:

Do you guys have photos of yours in? How do you maintain air tightness where flue passes thru wall?

 

[Gus Potter]

5 hours ago, ProDave said:

If the stove is 200mm from the finished wall, then the wall covering e.g plasterboard will be all you need.  you only need this heat shield if your finished wall is less than 200mm.  Is it?

Dave, can you go back and check the value of 200mm.

 

Woodburning stoves and timber frame are not good bedfellows so we need to be really careful here! Don't forget folk that if your house goes on fire, while you may get out safely your insurance comapny will look for any avenue not to pay out!

 

40 minutes ago, nod said:

It’s no great shakes to use a cement board rather than PB 

It is an I'll ask you to specify why you think you don't need an air gap to act as a thermal break between the heat shield and the timber frame. 

[ProDave]

5 minutes ago, Gus Potter said:

Dave, can you go back and check the value of 200mm.

The 200mm was the specified "distance to combustible material" specified for the OP's stove by it's manufacturer.  It is only 100mm for mine.  And plastered and painted plasterboard really does remain very cool indeed behind my stove.  I cannot imagine what would have to go wrong to ignite the plasterboard or the timber frame wall behind it.

[Gus Potter]

5 minutes ago, ProDave said:

The 200mm was the specified "distance to combustible material" specified for the OP's stove by it's manufacturer.  It is only 100mm for mine.  And plastered and painted plasterboard really does remain very cool indeed behind my stove.  I cannot imagine what would have to go wrong to ignite the plasterboard or the timber frame wall behind it.

No..  it was not.

 

Please re read OP, anyway it's something I aware of as I do lots of TF design so am cautious. I'm also cautious that folk may change the stove so unless you have that written into your O & M manual for the house (which I bet you don't have!) explicitly then you are being irresponsible, some young couples may buy the house, change the stove and not be aware. 

 

The ONLY time that you can maybe reduce the clearance between a TF and the back of the stove is when it also heats the water so the back of it does not get above 100 Celcius. 

 

5 hours ago, benben5555 said:

The fitter came out and was concerned

 

Good response from the fitter. 

 

 

 

[Gus Potter]

Bit of pragmatic advice for all.

 

On a TF house or thatched house fit a smoke detector in the attic void. It costs little ( I have it in my own house) and can save the day. 

 

There is a tendency for folk to dry logs in or around a wood stove, if they catch light then then what? 

 

I deal with lots of building regs.. some are a bit general and not practcable applicable in cases.. or make common sense.. but some are really good and it is wise to follow the good ones.

[Oz07]

7 hours ago, Gus Potter said:

 I'm also cautious that folk may change the stove so unless you have that written into your O & M manual for the house (which I bet you don't have!) explicitly then you are being irresponsible, some young couples may buy the house, change the stove and not be aware. 

 

 

 

It won't be his problem then or his insurer refusing to pay out. You can't allow for every eventuality. Wouldn't the new couple need hetas or bc to upgrade stove? Then hetas fitter would flag up the issues. You need gas safe when changing a boiler. 

[saveasteading]

On 14/10/2025 at 22:37, JohnMo said:

something like this 

These are also made for hot flues. The plastic is red for clarity. I can't remember what "hot" is defined as... basically anything more than ambient I think, but up to very hot from gas burner flues.