Reduce chimey stack

[TNDU]

We are looking to get a new roof next year and when we got roofers round to get a quote, one company said that it would be cheaper and more efficient to reduce the chimney stack and bring it below the tiles, that is knock off the chimney stack until it is only high enough to be in the loft.

Currently the old gas fireplace had been replaced with an electric fireplace so the chimney stack had already been capped on the outside with a a vent to stop damp.

The roofer suggestion sounds like a good idea but I would like to ask if we need ventilation to the chimney once the stack is reduced inside the loft? My husband thinks that as the chimney stack is no longer exposed to the element, there is no longer any need to ventilate it, is this correct? I am planning to get the roofer to put a mesh/grill over the stack opening in the loft to stop anything crawling into there as I don't want mice getting into the fire place via the loft!

Also does anyone know if I need planning permission or building regs to do this chimney stack work?

 

[Bonni]

Good question. When a chimney is no longer used and blocked off, a 9" square vent is fitted to the base of the chimney and a vent cap placed on the chimney pot. This is to allow warm air to draft up the chimney, otherwise the air in a sealed stack condenses which can cause damp.

When the stack is taken down to below tile level, I don't know. I'm pro chimney, so I like to keep them fully intact with a feature fireplace. So my best guess is, as lofts are vented, I imagine the stack would still need to be vented.

 

[johnny2007]

From experience I have seen redundant chimneys reduced to loft level and fully sealed at the top causing no problem at all.
Possibly the fact that they're open at the bottom helps with ventilation.
Said this, if it was my own house I would not cap it and as you suggested, use steel mesh to avoid vermin getting in there.
Not up to date with regs, but up to a few years ago you needed to notify building control for chimney removal, even partial.
However, I very much doubt there's any interest from any council to deal with a chimney taken below roof level.
Only problem could be a keen surveyor when you sell your house.
Indemnity insurance is cheaper than building control fees.

 

[George_engineer]

If the chimney is taking down to first floor ceiling and insulated over then you would not need to venitlate.

If it is still open to the cold loft then I would maintain ventilation.