If your chimney stack in Newmarket needs rebuilding, knowing your material options and understanding the real trade-offs will help you make the right call.
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A chimney rebuild means taking down the damaged section of the stack - from the flashing line upward, or from the roof line where damage extends lower - and rebuilding it using new materials. The finished job should include new lead flashings at the base of the rebuilt section, re-pointing of any brickwork below the rebuild, and a new or re-bedded pot and flaunching at the top.
A leaning, cracked or crumbling chimney is both a structural risk and a source of water ingress. Once water is getting into the stack in volume, it works its way into the roof space and the chimney breast below. A rebuild is the correct solution when repointing alone will not make the stack structurally sound or reliably watertight.
The majority of chimney rebuilds use clay facing brick, and for good reason. Brick is proven, long-lasting, and when matched carefully to the existing stack it is difficult to tell a rebuild has taken place. Clay brick handles the repeated wetting, drying, heating and cooling that a chimney experiences better than most alternatives.
The key variable with brick is the specification. A soft, low-density brick that might be fine for an internal garden wall is a poor choice for a chimney that sits fully exposed above the roofline. For a chimney rebuild, you want a dense, low-absorption facing brick - the kind rated for severe exposure. These cost more per unit than standard facing brick, but the difference in longevity is significant.
Matching the colour and texture of the existing stack matters too. Reclaimed brick from a salvage yard can be a good option on older properties where a new brick would look obviously out of place. The limitation with reclaimed brick is that the quality varies, and you cannot always be certain of the original specification. A roofer who knows what to look for can advise on whether a particular reclaimed brick is suitable.
The mortar used to rebuild a chimney is as important as the brick choice. A mortar that is too hard - a cement-heavy mix - will not flex with the movement a chimney experiences, and the joints will crack rather than allow any give. A mortar that is too soft will erode quickly from a fully exposed position.
For most chimney rebuilds, a lime-based mortar with an appropriate proportion of Portland cement gives the right balance: durable enough for the exposure, flexible enough not to cause the bricks to crack under thermal movement. On period properties - particularly anything pre-1920 - a higher lime content is usually correct to match the softer bricks typically used at that time. Using a hard cement mortar on soft old bricks causes the bricks to spall, because the mortar becomes harder than the brick and forces movement into the face of the brick rather than the joint.
Always ask what mortar mix will be used and why. A roofer who cannot give you a clear answer to that question is worth treating with caution.
New lead flashings are included as standard in every chimney rebuild we carry out. This is not an optional extra. The flashing is the seal between the rebuilt stack and the roof covering - without a sound flashing, water will track down into the roof structure regardless of how well the brickwork above is done.
Lead is the right material for chimney flashings. It is malleable, long-lasting, and can be dressed into complex shapes around the base of the stack. Code 4 or Code 5 lead sheet is standard for chimney flashings - thicker lead lasts longer but adds material cost.
Alternatives to lead do exist - mineral-surface self-adhesive flashing tape, for example - but these are short-term solutions used as repairs, not as part of a new rebuild. On a proper rebuild, lead is the correct specification.
The flaunching is the mortar haunch at the top of the stack that holds the chimney pot in place. On a rebuild, the flaunching is always replaced - old flaunching is removed with the stack, and new material is laid to bed the pot securely.
Chimney pot choice is relatively straightforward. A standard round-topped pot in a clay or buff finish suits most properties and is the most practical option. Taller pots help with draw on a working fireplace. If the chimney is redundant (no longer connected to a working fire), fitting a half-round ridge capping or a purpose-made chimney cap is worth considering - it keeps rain and birds out of the flue without the cost of maintaining a full pot and prevents the interior of the flue deteriorating from moisture.
This is a question that comes up on many properties where the original fireplaces have been removed or blocked. A full chimney removal (taking the stack down to below the roofline and making good the roof covering) removes the maintenance liability entirely and eliminates the risk of future water ingress through the stack. It does change the appearance of the property, which matters more on some buildings than others.
Capping a redundant chimney and rebuilding it properly keeps the original character of the building, and on older properties that can matter for planning purposes. A rebuilt and capped stack with adequate ventilation through the cap is a sound, low-maintenance outcome. The cost of a rebuild is higher than the cost of removal in most cases, but if you want to preserve the look of the property it is the right approach.
Removing a chimney is a more complex structural job than it sounds - the stack often ties into the roof at several points and the roof covering needs to be relaid properly once the stack is gone. It is not a cheaper option in all circumstances.
We carry out chimney rebuilds across Newmarket and the surrounding area. If your stack needs attention and you want a clear view of the options before committing, call us to arrange a roof survey.
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Call any time. Calls are answered day and night and passed straight to our roofers.
