Chimneys & flues
Restoring warmth
Fireplaces are a defining feature of many period homes but bringing chimneys and hearths up to modern safety standards while remaining sympathetic to the original building is something that requires careful consideration. David Wright, residential sales and marketing manager for Schiedel, takes a look at some common issues that can occur and how they can be resolved
running costs. From grand inglenooks to small open fires in bedrooms and sculleries, its not uncommon for large period homes to have many chimney stacks adorning their roofs.
O Striking a balance
Any decent restoration must remain sympathetic to the fireplaces original design and use, but in the case of a listed property, works carried out must comply with certain legal restrictions.
Buildings of special architectural or historic interest began
to be protected after the Second World War as part of the post-war regeneration and there are now close to half a million listed buildings in the UK, 9,000 of which are Grade I listed.
In addition to celebrating a building’s special architectural and historical significance, listing brings a building under the consideration of the planning system to protect the structure and features and preserve the building for future generations. This can present challenges when restoring old fireplaces and a delicate balance must be struck between modern technology, higher efficiency standards, and the legal requirement to preserve the original character of the chimney.
Historical issues
The most common chimney and flue construction on period properties is soft clay bricks fixed with lime mortar and finished with a terracotta chimney pot. While these materials allowed the chimney to breathe, they are particularly susceptible to erosion if maintenance is neglected. On the external chimney stack, damage from long-term exposure to the elements will be clear to see from the ground or with a pair of binoculars. If repointing or rebuilding is required, a lime mortar must be used as non-breathable alternatives such as cement will simply lead to further problems. Inside, many chimneys were lined with a rough coat of lime mortar to prevent flue gas leakage; a practice known as pargetting. Over time this soft lining can become loose and cracked, with chunks becoming dislodged as flues are swept, leaving the chimney in a pretty poor state. Additionally, the inside of the chimney is subject to the chemical reactions of
June 2019
ver the years, many period fireplaces have fallen into disrepair as old buildings were neglected, damaged during the wars, or closed off to avoid spiralling
the flue gases, which, when combined with moisture from condensation or water penetration, produce a weak sulphuric acid which slowly eats away at the internal brickwork and mortar. In general, older properties present a greater fire risk, with
heat transfer presenting heightened combustion issues as often roof joists and other timbers were built into the structure of the chimney, a problem that’s exacerbated when combined with roofing materials such as thatch. This risk can be mitigated by using an insulated flue lining. Pumice, for example, offers excellent insulation and is highly resistant to temperature change. There are also specific flue pass thru solutions designed to ensure safety and efficiency in timber framed properties.
Modern solutions
In most cases, the most effective solution is to reline the entire chimney, which will provide an airtight, efficient means for the waste products of combustion to be released. There are several options: • Flexible stainless-steel liner – this is great option for relining chimneys, particularly those that house multiple flues. Flexible twin-walled liners can easily be fed through the existing chimney, snaking around minor bends to provide a seamless, corrosion resistant lining. The outer skin of the liner is corrugated with engineered joints for strength, while the inside skin is smooth, minimising soot collection and allowing for easy sweeping. • Liquid sealant – If chimneys are large and access isn’t so much of an issue, a liquid sealant can be used. Applied under pressure, the coating is forced into cracks and fissures, strengthening the flue wall and providing an effective seal. • Pumice systems – pumice is an extremely robust material which is highly resistant to temperature variations, minimising heat loss and providing excellent efficiency. Installing a pumice liner in an existing chimney usually involves creating access points at various places along the chimney in order to introduce sections of the liner, which are stacked on top of one another to create a secure internal lining. In thatch properties, liners boasting superior insulation can help ensure safety and appropriate insurances. Breathing life back into these long-neglected fireplaces
requires special consideration in terms of materials, techniques and finishes. Historic damage must be carefully assessed and rectified to ensure the future of the building and the safety of its inhabitants.
www.heatingandventilating.net
www.heatingandventilating.net
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