Author Topic: Ventilating blocked-up fireplaces  (Read 523 times)

Ventilating blocked-up fireplaces
« on: September 24, 2020, 09:40:04 pm »
The tumble dryer thread got me thinking more about the (lack of) effective ventilation in my flat. It's a conversion within a Victorian townhouse (5 floors, 5 flats, we're second from top). All fireplaces have been blocked up, except the living room one which has been replaced with a delightful 1990s gas fire at some point. None of them have airbricks/vents of any sort.

I'm thinking this is probably not optimal for airflow (in our previous house, the builders who did a load of renovation work installed vents in the fireplaces, as those didn't have them either). However, I'm not sure the best way to go about it.

They sound hollow when tapped, so likely to be boarded and reasonably easy to hack apart. I've long fancied opening them up and reinstating proper fireplaces (if only for decoration), but I'm slightly worried about what I might find. I fear that my dreams of revealing original cast iron beauties are highly unlikely to come true.

For those who might have experience of this sort of thing - is it simply a matter of cutting a suitable hole and getting an appropriate size vent - and does it need to be one of those hit & miss type ones? The ones we had in the last house were like this (ugly). Is bigger better, or will it just make things draughty?

Re: Ventilating blocked-up fireplaces
« Reply #1 on: September 24, 2020, 10:28:18 pm »
Years ago just bunged brick-sized gaps in that I covered with a nice oak grill from B&Q.  Never noticed a draught but it would probably be air drawn into the flue and get into the house from elsewhere.

More recently as part of pointing work we had our chimneys capped with a proper cowl to prevent birds falling down.  This would reduce any draught.
Sic transit and all that..

Re: Ventilating blocked-up fireplaces
« Reply #2 on: September 25, 2020, 12:24:08 am »
Disused chimneys should indeed  be ventilated, I would though  be wary of cutting into anything  built into an older house before an inspection for asbestos cm's. Our house was built in the early 1980's and we had asbestos cement boards above and below the gas fire / back boiler.

Re: Ventilating blocked-up fireplaces
« Reply #3 on: September 25, 2020, 09:38:45 am »
Get a vent that is permanently open, doesn't need to be adjustable (or just reinstate the fireplace).  It may be cement board, but far more likely to be plasterboard or ply.  If it's cement board (tapping it will sound distinctly "hard") remove it whole and replace it - use a decent respirator, disposable overalls, and damp it down to reduce dust.  Check your local tip - ours takes limited quantities for free.
We are making a New World (Paul Nash, 1918)

Re: Ventilating blocked-up fireplaces
« Reply #4 on: September 25, 2020, 09:45:01 am »
Are the chimney's capped?

If not, then installing ventilation would be a good idea. Not sure I'd pick permanently open - there are plenty of ventilation grills that allow for adjustment. You might install one and find you've created a howling draught and would want to part shut it off.
<i>Marmite slave</i>

Re: Ventilating blocked-up fireplaces
« Reply #5 on: September 25, 2020, 10:30:24 am »
From installing a gas fire in a past property and a wood burner in my current one, I’m pretty certain Building J Regs dictate this is law to have a vent. There are other extras for a wood burner as you may imagine.

If it is rented, the owner is not complying and this is an issue.

Re: Ventilating blocked-up fireplaces
« Reply #6 on: September 25, 2020, 10:46:32 am »
From installing a gas fire in a past property and a wood burner in my current one, I’m pretty certain Building J Regs dictate this is law to have a vent. There are other extras for a wood burner as you may imagine.


Venting an unused chimney to prevent damp isn't something I'd expect building regs to cover - venting a room where there is an open fireplace/wood burner yes (we have an airbrick in the outside wall and an underfloor vent to a recessed Baxi grate)..
We are making a New World (Paul Nash, 1918)

Re: Ventilating blocked-up fireplaces
« Reply #7 on: September 25, 2020, 10:50:34 am »
From installing a gas fire in a past property and a wood burner in my current one, I’m pretty certain Building J Regs dictate this is law to have a vent. There are other extras for a wood burner as you may imagine.


Venting an unused chimney to prevent damp isn't something I'd expect building regs to cover - venting a room where there is an open fireplace/wood burner yes (we have an airbrick in the outside wall and an underfloor vent to a recessed Baxi grate)..
Sorry. I was thinking about the gas fire. So if that is not in use, you are 100% correct.

Re: Ventilating blocked-up fireplaces
« Reply #8 on: September 29, 2020, 05:01:19 pm »
You need to acertain which flue the gas fire is using and make sure you dont ventilate the same flue above the gas fire. (it may be using a Copex  liner). You can have more than one flue in the same chimney brest.
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