David Wright, Residential Sales & Marketing Manager for Schiedel looks at the options to make chimneys on existing housing stock safe and suitable for 21st century wood burning.
During the 1960s and 70s fireplaces largely fell out of use, as central heating became the most popular means of heating our homes – many were removed or bricked up. In more recent years open fires have come back into fashion and an increasing number of homeowners are keen to reinstate fireplaces in period properties restoring grates or installing new wood-burning stoves, for a more efficient wood heating solution.
The vast majority of traditional chimneys and flues were built from relatively soft, porous clay bricks and lime mortar, finished with a terracotta chimney pot, which is particularly susceptible to frost damage and tends to erode. If neglected, the inside of the chimney suffers too as it is subject to the chemical reactions of the flue gases within. These gases contain sulphates and when combined with moisture, from water penetration or condensation, produce a weak sulphuric acid which damages both brickwork and mortar on the inside, leading to further erosion.
In the past, efforts were made to make chimneys airtight – to minimise any leakage of flue gases – and flues were ‘parged’ or ‘pargetted’ internally, with a rough coat of lime mortar as they were built. This pargetting deteriorates over the years and becomes loose and cracked, dislodging as flues are swept.
External chimney repairs tend to be relatively expensive as scaffolding is nearly always required. Internal chimney repairs are impractical, due to the challenges presented by the lack of space, so it is widely agreed that the most effective solution is the introduction of a new modern flue or chimney liner, which can provide an airtight, efficient means for the waste products of combustion to be released up and out of the house. Here are some examples:
Stainless Steel Flexible Flue and Chimney Liners
Flexible stainless steel lines are particularly useful for situations where there are multiple flues within a chimney. If you count the chimney pots on top of the chimney, you’ll get an idea of the number of fireplaces the chimney originally serviced and a flexible liner enables you to snake the flue through the chimney and connect to the correct fireplace.
Our Tecnoflex Plus flexible chimney liner is a versatile product designed to be used with gas, oil and multi-fuel appliances. The liner has a corrugated outer skin and engineered joints to give it strength and the smooth inner skin allows for easy drain down of condensates so there is less opportunity for soot to collect in the joint areas – it is also easy to sweep.
Alternatively, chimneys can be coated inside with a product such as Schiedel’s Isokoat. This works well in old chimneys were the mortar joints between the bricks or stonework have failed. Over time, lime mortar becomes porous, turns sandy and crumbles away so in order to prevent the poisonous fumes, tars and condensation leaking into the home, a physical barrier is required. Isokoat, a liquid sealant, is applied to the inside of the chimney under pressure so that it is forced into the cracks and fissures, strengthening the flue wall as well as offering an effective seal.
Sometimes, historic properties in particular demand something a little different. Billing Chimneys in Ringwood, Hampshire are specialists with over thirty years’ experience in chimney design, construction, repair and maintenance; particularly on period homes. They often work on thatched properties where the need for a safe flue lining is paramount. Many insurance companies now specify a requirement for an insulated flue in thatched homes, designed to provide improved protection to the property in the event of a chimney fire. The high temperatures that can be reached within the flue itself also need insulating to prevent heat transfer, which in itself can lead to a fire, so the situation is a challenging one.
In such cases, Billing Chimneys specify pumice liners such as our Isokern system, which offers superior insulation. A structural register plate is installed at a discreet height within the chimney recess to support the pumice liners and the surrounding insulation that is used to fill the void between the existing brick or stone chimney and the new liner. The excellent insulation properties of pumice ensure that the flue temperature is kept at a safe, even-level, along the entire length of the flue.
With such practical and innovative solutions readily available, there’s no reason why old chimneys can’t continue to make the fireplace the heart of the British home.