Chimney Stack Extension?

[DM81]

Hi,

Im new to this forum so please bare with me.

I've recently started the ball rolling regarding a loft conversion with en suite bathroom. I understand they can be quite tricky with regards to building regs etc.
All going well untill yesterday when architect emailed to say building control have informed him that my chimney stack needs to be extended due to me having a very seldomly used gas tiled insert open fireplace in the dining room.
Apparently the stack was reduced in height at some point for some unknown reason.
Now I can get my head round the whole fumes may enter the house at loft height if the height of the chimney / flue is not sufficient enough, although I really dont see what a couple of extra feet is going to achieve. Anyway the architect has informed me that I must have some structural calcs draughted up and a plan for extra restraint via the very expensive structural eng he uses, to compensate for extra load etc and increase the height of the chimney stack back to its original height. The only other option is to brick the fireplace up which we obviously dont want as it serves purpose.
I have done a little research and it turns out there may be a possibility we could install a power flue? Would this be correct? I know I may have to fit a complete fire place to allow for this or is there a possibility a universal type power flue can be purchased and fitted to my existing fire.
I would prefer to do this opposed to fitting a ballanced type flue and have to change the design of the whole fire place with a glass front etc.
Another question would be would it be possible to extend the flue and disguise with a clay chimney pot opposed to the complete chimney stack I dont understand why the chimney stack needs to be extended. Also if a balanced flue or power flue can be fitted with a short extension facing away from the house then how and why must I extend the chimney flue when its at least 2 metres off the pitch of the roof.

Any advice will be whole heartedly appreciated many thanks and kind regards

D

 

[Architexeter]

The B.regs you are up against are in Part J of the Approved Documents. Available on planning portal / google "AD part J".

There are two sets of regulations, one for solid fuel appliances (p31) and one for gas burning appliances (p49 & 50). For a gas open natural draught (my assumption) it refers to a BS document or "Should not be used"!

I guess the flue could be extended with a stainless steel flue, my house has one that is about 1.8m long but it sure is ugly and had fixings to adjacent roof.

It may well be better/cheaper to install a log burner and ditch the gas fire.

Hope that helps

 

[DM81]

The B.regs you are up against are in Part J of the Approved Documents. Available on planning portal / google "AD part J".

There are two sets of regulations, one for solid fuel appliances (p31) and one for gas burning appliances (p49 & 50). For a gas open natural draught (my assumption) it refers to a BS document or "Should not be used"!

I guess the flue could be extended with a stainless steel flue, my house has one that is about 1.8m long but it sure is ugly and had fixings to adjacent roof.

It may well be better/cheaper to install a log burner and ditch the gas fire.

Hope that helps

Ill give the regs a once over thanks for the assitance.

With regards to the log burner I have a solid fuel fire in an other room. Im not against the idea, but would this not require a similar flue length. I would have thought the fumes from this would be more severe than a gas fire.

 

[nipper39]

I am a gas safe registered engineer and currently taking hetas course , flue heights are set out in part j of building regs , chimney heights are important due to positive and negative pressure zones created when wind blows round buildings. Reducing stack hieght can lead to flue gases been blown back down the flue .the regulations set out spacific flue heights and locations in order to avoid these problems , for the sake of a few bricks its not worth the risk.whem you add a dormer you may cause a difference in how wind passes over and around a flue, so special measurements are set out in regs to avoid this.

 

[nipper39]

Also you can get stainless extentions with a fake brick or stone sleeve to make them look better

 

[DM81]

Also you can get stainless extentions with a fake brick or stone sleeve to make them look better

Hi thanks for the advice, you wouldnt happen to have a link for something like that would you.
I'm currently looking through the regulations and can't find anything in particular on chimney stack height. I have found something regarding the flue opening being at least 1m higher than any windows or openings if a dormer of roof light is fitted.
I thought maybe if an extension is fitted to the original flue then a clay pot or something could hide some of it's ugliness.
I dont know what to do for best I suppose it all depends on cost, I dont mind paying for the works if thats what is required but I can't get my head around why the structural eng needs to submit calcs for extra support if the chimney has at one point been sufficient height.

 

[DM81]

I've Searched and searched for info regarding masonary chimney stack lengths, and am struggling to find anything that states that it must be a certain length.
I understand that the length of the flue is definately an important factor so opposed to extending my chimney stack and having structural calcs drawn up and plans to extend via the architect. I will suggest extending the flue and disguising it using a clay pot. I'm sure that if anything it will only require lengthening 1m to take it over the height of the ridge.
In the reg's it states that the as long as the "flue" extends 2.3m from where it exits the ridge things should be ok and obviously my chimney stack starts at the eves of the house and terminates close to the ridge, surely this with a 1m extension is enough.?

 

[nipper39]

Hi I understand you confusion the 2.3 m relates to the distance from the base of the terminal (pot) to the pitch (tile slate etc) horizontally. Or 600mm above ridge .where a dormer or extention is fitted the base of the terminal (pot) mustmbe a minimum of 1 meter above the top of any opening (window or vent) in the dorma or extention ill get link for flue extention and post tommorow

 

[nipper39]

One other thing and yes I think this is stupid too, a pot is a terminal and is not used in the height calc , but a peice of stainless is a flue and therfore if it has the correct cross sectional area as your exsisting chimney would count , the stainless would have to be twin wall insulated

 

[nipper39]

The link you need is www.kevington.com you want prefabricated grp chimneys you cant get lighter than fibre glass they sell them with gas flue pipe built in and are suitable for all building regs[/url]