Need Advice on New Concrete lined Chimney Please

[ebaxter]

HI, Hope I'm posting in the right place. My builder has built a new chimney into an extension I am having. He has used 9" concrete flue liners and enclosed these using masonry and then backfilled the voids with vermiculite.

My concerns are the proximity of the floor joists and also the roof joists almost without exception they are either touching or an inch away. To add to this the back wall has been used as the back of the masory to enclose the flue and where it gets to the wall plate rather than cut out the wood and replace with masonry they have literally built up on it.

I have googled alot and know I probably need to spean with m,y building officer but before I do this and potentially get told to take my chimney down I wanted to know if I have any other options.

My architect by the way had specifed a a doub;le skinned insulated flue. My builder is telling me he is now going to put a double skinned flexible liner down and used vermiculite around this and he thinks thats ok.

Is it? Do I have other options or am I clutching at straws? Any advice greatly appreciated.

 

[mointainwalker]

After this double-skinned kiner goes down, what diameter of flue will be left ?

What was specified initially - both for this and clearance from rafters ?

 

[swingles]

Ask your architect.

 

[ebaxter]

Flexible flue liner that builder wants to put in in 6" so we can connect the stove this will leave arounabouts 1.5" in theory around the diameter which he is goin to try to backfill.

The architect specified a double skinned rigid insulated system which maybe wasn't very clearly stated although he did state a minimum 50mm clearance from combustables or whatever the manufacturer specified.

The builders suggestiong leaves us with a flexible 6" flue pipe insulated if poss inside a 9" new concrete liner that has approx 2" of vermiculite around it. Three sides of the chimney then have 100mm masonry before we get to timber. IT's the fourth side that doesn't have this extra 100mm.

Reading Building regs it states 200mm from inner face to combustibles or 40mm air gap from outside of chimney. The builders proposal is doubling up of which there is no extra guideline for so I'm stuck.

I can get the Building Officer in but before we get tolds to take the whole thing down I want to explore other safe options if I have any?