Blocking up disused chimney

NoisyGiraffe

I recently bought my first house and have little experience so please forgive my lack of knowledge!

I've had the gas fire taken out of the living room and plan to block up the chimney breast and plaster over (as it is upstairs). My understanding is that the chimney should be capped, swept and then vented at the bottom during this process to prevent any future damp issues. I have 2 questions:

1. Is is possible for the air vent be placed under the floorboards in to the space underneath or does it just need to be on the lower wall of the chimney breast but above the flooring? They're not the best looking things so if I can hide it I'd prefer to do that! 

2. I think (from googling) the chimney currently has a gas terminal, see photo below - our chimney is the one on the right. Does this need to be changed to an actual cap or is this enough to keep the rain out and allow ventilation? 

FreeBear

The chimney pot looks like it can be left as is - You may well find a thin metal liner going up the flue, and the chimney had been swept when it was installed. So you may not need to have it swept..

Fitting a vent under the floor - Whilst on paper, it could work, you will find it more trouble than it is worth. There will be a concrete slab some 125mm thick that fills the fireplace and projects out in to the room by 400mm or so. This slab will be set on to a fairly large chunk of masonry forming part of the foundations - If you are going to remove the hearth, then a vent below the floor would work - You could use the opportunity to put proper floorboards down.. Do be aware that you'll probably need to take the brickwork down below the DPC level, so any joists put in would need protection from damp rising up from the ground.

NoisyGiraffe

FreeBear said:

The chimney pot looks like it can be left as is - You may well find a thin metal liner going up the flue, and the chimney had been swept when it was installed. So you may not need to have it swept..

Fitting a vent under the floor - Whilst on paper, it could work, you will find it more trouble than it is worth. There will be a concrete slab some 125mm thick that fills the fireplace and projects out in to the room by 400mm or so. This slab will be set on to a fairly large chunk of masonry forming part of the foundations - If you are going to remove the hearth, then a vent below the floor would work - You could use the opportunity to put proper floorboards down.. Do be aware that you'll probably need to take the brickwork down below the DPC level, so any joists put in would need protection from damp rising up from the ground.

Thanks for this, I see what you mean about it being more trouble than it's worth! Might just keep it simple and go with the vent in the wall above the floor and skirting.

When the engineer took the gas fire out there was quite a lot of dust/debris behind the back plate (see pics) and he said the fire probably hadn't been serviced for about 10 years for that to build up. This is what made me think it needs to be swept. I can't seen any metal liner up there.

FreeBear

Much of that debris looks like it might be mortar - A good sweep would be worthwhile. When you block up the opening, do it in such a way that it can easily be undone. The next owner might like to install a small wood stove (another reason for not getting rid of the hearth).

As for a vent at the base - It need not be a huge hole. Just enough to allow some air to circulate.

TELLIT01

An internal air vent won't protrude much from the wall, certainly not as much as the skirting will, assuming you plan to complete the skirting.  You can stand furniture in front of the vent without causing any problem, as long as there is some space between the vent and furniture.

NoisyGiraffe

FreeBear said:

Much of that debris looks like it might be mortar - A good sweep would be worthwhile. When you block up the opening, do it in such a way that it can easily be undone. The next owner might like to install a small wood stove (another reason for not getting rid of the hearth).

As for a vent at the base - It need not be a huge hole. Just enough to allow some air to circulate.

Thanks for this, I'll sort out getting it swept and will leave the hearth in place. Would this vent (https://www.toolstation.com/adjustable-vent/p37571?store=B2&utm_source=googleshopping&utm_medium=feed&utm_campaign=googleshoppingfeed&gclid=EAIaIQobChMIuMSd7uz06gIVDbDtCh37EgAEEAQYAiABEgINx_D_BwE) be ok size wise? Or too big/too small? 

Slinky

We're doing similar, except when we looked up our chimney last weekend, we found quite a lot of soot so the sweep comes next week. We've had problems with the salts in the soot affecting the plaster on the chimney brest in the room above. It was replastered and is still bobbling up and flaking, hence why we are having it swept.  We have asked the builder to knock through the back of the fireplace and put the airbrick on the other side, which will be under our stairs and much less visible.  Is this a possibility for you?

ETA our sweep will charge us £35

NoisyGiraffe

Slinky said:

We're doing similar, except when we looked up our chimney last weekend, we found quite a lot of soot so the sweep comes next week. We've had problems with the salts in the soot affecting the plaster on the chimney brest in the room above. It was replastered and is still bobbling up and flaking, hence why we are having it swept.  We have asked the builder to knock through the back of the fireplace and put the airbrick on the other side, which will be under our stairs and much less visible.  Is this a possibility for you?

ETA our sweep will charge us £35

Ahh no, I've got neighbours behind my chimney! Good thinking on your part though! I think I'm going to have to go with tellit's suggestion above of putting something in front of the vent to disguise it. 

Thanks for adding the cost of the sweep, I'm just looking into finding one now so it's good to have a ballpark figure