Can I vent a disused fireplace through suspended floor?

wilco88

wilco88

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Hi,

I know old fireplace/hearth questions are talked about on here a lot but i don't think this question has been answered, or if it has, not comprehensively.

I have taken out the concrete hearth of an old disused fireplace, in preparation to re-lay the original t&g flooring throughout the room.
The fireplace is bricked and boarded up and has had a vent installed since being boarded up (probably in the 1970's).
Despite this there are signs of damp coming through the wallpaper (wallpaper will be removed eventually).

When i dug up the hearth, the soil and rubble was very damp and there were signs of plant growth (small roots etc).

I plan to dig out the rubble and soil to create a good air space. The rest of the suspended timber floor is well ventilated.

Instead of venting the chimney stack via an internal wall vent (as is currently the case) can i make use of the well ventilated suspended timber floor void and vent the chimney through the floor by removing the hearth completely and having the base of the fireplace fully open to the void below the floor?
 
wilco88 said:
Hi,

I know old fireplace/hearth questions are talked about on here a lot but i don't think this question has been answered, or if it has, not comprehensively.

I have taken out the concrete hearth of an old disused fireplace, in preparation to re-lay the original t&g flooring throughout the room.
The fireplace is bricked and boarded up and has had a vent installed since being boarded up (probably in the 1970's).
Despite this there are signs of damp coming through the wallpaper (wallpaper will be removed eventually).

When i dug up the hearth, the soil and rubble was very damp and there were signs of plant growth (small roots etc).

I plan to dig out the rubble and soil to create a good air space. The rest of the suspended timber floor is well ventilated.


Instead of venting the chimney stack via an internal wall vent (as is currently the case) can i make use of the well ventilated suspended timber floor void and vent the chimney through the floor by removing the hearth completely and having the base of the fireplace fully open to the void below the floor?
Click to expand...

You need through ventilation and the negative V's positive pressures associated would not give you the ventilation you need, drawing from the sub floor alone - i.e. you still need it open at the top. This is of course depending on what the actual problem is. Poor quality initial build i.e. lack of DPC in the stack is often to blame and nowt to do with through draughts. Other problems is saturated masonry i.e. hygroscopic salts etc.
 
OK.
I intend to vent at the top too, of course.

So with venting at the top, it's not the worst idea in the world to vent through the floor space? Given that the floor space is very well ventilated already.

Yes - will check DPC in the stack as well.

Thanks.
 
wilco88 said:
OK.
I intend to vent at the top too, of course.

So with venting at the top, it's not the worst idea in the world to vent through the floor space? Given that the floor space is very well ventilated already.

Yes - will check DPC in the stack as well.

Thanks.
Click to expand...
Venting through the floor will provide a stronger through draught, yes.
 
Yes, sounds like a good idea. I'd just fit a couple of air bricks to communicate with the void though, rather than leave it open ,as you might get birds etc ending up down there..
 
Bullet-Proof_Biscuit said:
Yes, sounds like a good idea. I'd just fit a couple of air bricks to communicate with the void though, rather than leave it open ,as you might get birds etc ending up down there..
Click to expand...

A mesh at the chimney would be a better way to keep birds out completely, than preventing their access from the stack to the under floor area.
 
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