Case Study 1 - Standard Chimney Relines and Chimney Relining
We treat local clay brick chimneys constructed between 1750 and 1965 with an internal flue size from 225mm to 350mm as ‘standard chimneys’. The structures were usually built to last by craftsmen who understood the importance of a good sound chimney. The use of coal with its corrosive soot deposits and high heat output has attacked the original bricks and mortar for many years. Combined with weathering from the elements, it seems ridiculous that these chimneys could be used for any type of modern appliance without relining.
The images above and below left show a chimney built in 1962. You can see the remnants of the original mortar that was smeared inside the chimney walls during construction. The top part of the chimney is exposed brickwork and the brick mortar is weakening. The cement based mortar used has less acid resilience compared to the lime based mortar used in older properties.
The images above and below centre show a chimney built in 1920. The original mortar has turned back to sand and you can easily push your finger into the brick joints.
The images above and below right show a chimney built in 1857 . The mortar has completely disappeared in places, especially between the bricks that partition the neighbouring flues. Only the external pointing and gravity is keeping the structure from collapse! We do not recommend to hang a class 1 chimney liner (using ‘pot hanging’ components) from a chimney pot that sits on top of these structures. We always remove the chimney pot and carry out any remedial works needed to the brickwork when relining for a class 1 chimney unless; the pot is set deeply into the brick structure which is sound and enables the passage of the poured insulating backfill.
A good quality job can not be completed if the fitter is standing on tip toe to reach the work area while hanging on to a ladder for dear life. Every part of our work requires risk assessment. A man can not give the high levels of workmanship needed if he is not comfortable, doesn't feel safe or cannot reach to see his work. We combine ladders, in house scaffolding, our own powered access equipment and high levels of working at height training to ensure the safety of the public, our workforce, our customers and their properties.
The liner is fed into the chimney until there is a complete length from top to bottom. The liner should never be forced as this will damage it. Occasionally the liner will not pass through because of a tight bend or other obstruction, in this case a hole may have to be made in the chimney stack. We always make good these holes and re-plaster except decorating, this is a normal and necessary part of our working day. We support the liner from the bottom with a steel plate that sits on heavy duty steel angle securely fixed to the surrounding brickwork, (a couple screws is not sufficient).
Once the liner is in place and the register plate sealed, we pour an insulating loose fill vermiculite into the void around the flue liner. The insulation keeps the smoke warmer as it passes through the liner reducing tar build up. Insulating reduces condensates in and around the flue, holds the flue into place and quietens howling chimneys.
The preferred way to finish the top of the chimney is to add a top plate and clamp, other methods may be used depending on site specifics. The chimney pot is bedded on top of the plate with securing mortar to seal.