Blocking off unused pre-cast flue

[Mike Atkinson]

Can anybody point me at any advice/regs regarding blocking off an unused pr e-cast flue?

We inherited a centrally heated house with an additional gas fire in the lo unge. However its supply was later capped off as the metal flue pipe in the loft was leaking. We frankly don't need the additional heat - the wall up the stairs was also worryingly hot if the fire was used - and now want to r eclaim wall space by removing the essentially condemned fire and its surrou nding fireplace. This isn't inset - it just butts against what I assume are the pre-cast flue blocks going up to the attic.

I'd live to squirt expanding foam up the bottom of the flue and then make g ood the wall, but I suspect that is insufficient ;-). What needs to be done ? Does the old flue need to be vented at the bottom? If so, how lounge (wif e!) friendly can this look? The other side of the bottom of the flue is in the cupboard under the stairs. If a vent is needed, could the requisite ope ning be there?

Do I have to remove the top of the old flue from the roof apex? Can it not be left?

Many thanks in advance for any advice!

Mike

[Andrew]

Just remove the flexible pipe inside the loft (but it could be asbestos cement) and shove some loft insulation inside the angled flue block in the attic. If you are going to remove the false chimney breast in the lounge (opens up the room nicely) then make sure the upstairs floor joists aren't sitting on it (as mine were). If so you'll need to extend them into the wall. Then you will need to hack off the projecting part of the angled flue block behind the false chimney breast (that the fire or backboiler connected to). If it is in a party wall then filling it up with concrete will improve the sound insulation that you are diminishing by removing the false chimney breast.

[Mike Atkinson]

Thanks. You think no ventilation is needed at the bottom end?

There isn't one! It's just a wall. Until I looked up pre-cast flues I thoug ht this was some after-fit solution, but I guess this was in place from con struction. In the lounge I have a normal wall, and although there is a mant elpiece and fireplace surround, both project from the wall and don't appear to be built-in or inset. Inset wouldn't be possible anyway - the wall is a bout as thick as a brick length; I don't believe there's any cavity as it's not thick enough.

[Andrew]

It was never used for coal or wood. Gas burns quite cleanly and the flue blocks are on the inner leaf, so isolated from the weather. QED just seal it at the bottom and plug with some thing vapour permeable at the top, like a plug of rockwool.

You browser seems to be posting lines longer than 79 characters for some reason. Thunderbird not happy, and sig may have vanished.

[Capitol]

IME single leaf flue blocks are only used for gas fires.

[Muddymike]

My Thunderbird is quite happy with it!

Mike

[Mike Atkinson]

My apologies if this is the case. I confess I'd forgotten about line limits from mu old Usenet days. All my messages are now sent in the "new" Google groups using Chrome. I've just been looking for any configurations options, to no avail.

[Martin Bonner]

You have to type the line breaks by hand. It's tedious.

[sarah]

Did you do this as I’m looking to do the same? I’m wondering how much breeze blocks make up the fake chimney breast and how much there would be to remove?

[Andrew]

You are replying to a 4-year old post !.

Class 2 flue blocks are 4 inches deep, so just form part of the inner leaf of a cavity wall. They are longer than a standard 18 inch block and apart from the 45 degree starter block above the original back boiler/fire you can just leave them in place. In the loft there will (or could) be another 45 degree exit block that is connected to a roof or ridge vent exit with typically asbestos-cement pipe, though older properties might have galvanised piping. Just stuff some rockwool into the 45-degree exit in the loft after removing any flue pipe. The matching 45 degree block that is behind the false chimney breast can just be bashed out and made good with normal blockwork. Then you can dispose of the false chimney breast too, though there is a possibility that it supported some of the flooring joists (mine did). These will need extending into the main wall.

[Mike Atkinson]

Sarah, yes, this was done, but by a contractor as part of some larger work. Note we didn't have any false chimney breast - just a plain wall - so I'm afraid I can't advise further. Good luck!