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Chimneys & Fireplaces

Effectiveness of flue repair


When my house was built 30 years ago, the chimney draught was excessive and the builder drilled a hole in the flue and fitted a grill outside on the chimney stack to reduce the up draught. This didn’t work and he plugged it again. After that, there was a smoke smell in a bedroom and he fixed it again. It worked after that. We now use a decorative gas fire and I have co detectors in the bedrooms. I’m going to have the chimney repointed along with the rest of the house. The pointer uses an angle grinder. Would the vibrations dislodge the repair that was done years ago? If it does, are there any solutions as I’m worried about carbon monoxide? Any advice would be much appreciated. Thank you

5 Answers from MyBuilder Chimney & Fireplace Specialists

Best Answer

The angle grinder is the best way to get out the old cement / mortar , you will have more chance of disturbing the render if you use a hammer and chisel . Good idea about co alarms in bedrooms , I would put them at sleeping height


Answered 3rd May 2021

Hello I read the previous answer to your question and firstly I would like to advise you to ignore the advice given about moving your carbon monoxide alarms to sleeping height. So basically carbon monoxide is lighter than air so would be detected at ceiling height first , that is why most detectors that come with instructions advise you to fit them about 150mm from the ceiling. Secondly your gas fire (hopefully) would of been fitted by a registered “gas safe” engineer and he would of adhered to all safety measures and building regulations . Lastly “raking out” the old mortar with an angle grinder is less severe than a hammer and chisel so is less likely to dislodge anything. However when the pointing work is complete you could always ask a registered “gas safe” engineer to call and give the gas fire a service and check all emission out puts and venting just to be sure. Hope this helps ?


Answered 6th May 2021

The previous statement is indeed correct, a 4.5 inch angle grinder with a wide blade is he best solution for raking out the joints in a chimney. It will cause least disruption to the afore mentioned ventilation in the chimney. We would however always recommend lining an existing chimney in any property over 20 years old. With regards to the Carbon monoxide alarms, they should be located within a 3 meter radius of the appliance in all cases and if they are to be ceiling mounted 300mm from the wall, if wall mounted 150mm from the ceiling. The HETAS team will be able to help you with any other details you may need and ensure the chosen installer of your gas fire is GasSafe registered.


Answered 31st May 2021

The only difference i would give to that answer is co alarms should be fitted above door and window height and max no higher than six inches from ceiling . Regards Robert distinctive fireplaces


Answered 31st May 2021

Co alarms should be 6 inches from ceiling height. If you line the chimney with a flexible stainless steel flue liner it will solve all of your issues at once.


Answered 31st May 2021

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