Chimney repairs

The short answer

Chimney repairs cover repointing an eroded stack, renewing the flaunching that holds the pots, replacing lead flashings where the stack meets the roof, and capping or venting a disused flue. Damp on a chimney breast, loose mortar in the garden and staining on the ceiling below are the usual signs. Cost is driven mostly by access, since almost all stack work needs scaffolding.

What the work involves

Typical work is raking out and repointing eroded joints in lime or cement mortar, renewing the flaunching, replacing cracked pots, fitting cowls or vented caps to unused flues, and renewing the lead soakers and apron flashing at roof level. Severely leaning or eroded stacks are sometimes rebuilt from a sound course upwards.

Rules and consents in Scotland

Repair is normally exempt from a building warrant, but removing a stack, altering its height, or changing a flue in use for a gas or solid-fuel appliance brings building standards and appliance regulations into play. Listed buildings and conservation areas generally require original stack profile, pot type and lime mortar to be retained.

What commonly goes wrong

Sealing a disused flue completely without ventilation, which traps moisture and causes damp on the chimney breast; and hard cement pointing on soft historic stone, which forces moisture into the masonry.

What it usually costs

Indicative ranges only, to help you judge a quote. They are not an estimate for your property — only the business doing the work can give you that.

• Scaffolding to stack height is usually the single biggest item on a chimney invoice.
• Repointing is priced by the extent of the stack; a full four-sided stack costs more than one weathered face.
• New flaunching and pot replacement is a moderate additional cost when scaffolding is already up.
• A full stack rebuild costs several times a repoint, so it is worth combining stack work with other roof repairs in one scaffold visit.

What to do, in order

1. 1Have the stack photographed close-up before agreeing any work.
2. 2Ask whether the mortar specified is lime or cement, and why, for a pre-1919 building.
3. 3Combine stack work with any other roof repair while the scaffolding is standing.
4. 4Cap unused flues with a vented cowl rather than sealing them.
5. 5Have any flue that will serve an appliance swept and tested before it is used.
6. 6For a tenement, confirm the cost-sharing position before instructing.

Local detail for the Lothians

• Edinburgh tenement stacks are typically large multi-flue structures shared between several flats, so both the repair cost and the decision are usually shared.
• Sandstone stacks in the New Town and Marchmont need lime mortar; cement repointing accelerates decay of the stone.
• Many Lothians homes have disused flues from removed fires — venting rather than sealing avoids damp on the breast.
• Exposed stacks in high-lying areas such as the Pentland fringe and East Lothian coast weather faster than sheltered inner-city ones.

When you need a professional

A roofer or stonemason for the stack, a HETAS-registered installer or gas engineer where the flue serves an appliance, and a surveyor for a leaning or badly eroded stack.

Common questions

Should I remove a chimney I no longer use?

Removal is more expensive than repair and can affect a period property's appearance and, in listed or conservation-area buildings, may need consent. Capping with ventilation is the common alternative.

Do I need scaffolding for chimney work?

Almost always, since safe working at stack height cannot usually be achieved from a ladder.

Related pages

• Roof repairs

  Slipped slates, failed flashings and leaks on Scottish pitched and flat roofs.

• Stonework and repointing

  Sandstone indenting, lime repointing and why cement mortar damages period walls.

• Damp problems

  Telling penetrating damp, condensation and rising damp apart before spending money.