Repairs: flues, fireplaces and chimneys

Flues, fireplaces and chimneys are common areas where repairs or more radical treatments are required. Hidden defects can rapidly eat into the budget for refurbishment works, distressing owners, occupiers or developers who have only a limited budget.

It is probably worth spending an extra 10 minutes of investigation time to check the overall structure of the chimney.

With pressure on space particularly affecting smaller old properties (typically the 2-bed terraced house) it is not uncommon to find that chimney breasts have been removed.

This may leave inadequately supported chimney masonry on upper floors, within the roof space and above the roofline.

If the works have been carried out properly, you should find substantial support – hopefully some form of steel joist, although sometimes timber is used. If the timber is of sufficient dimension, all is well and good, but this is not always the case. The author has often found chimney breasts supported (perhaps in the roof space), on nothing more than the ceiling joists or a few pieces of ‘4-by-2’ softwood.

• The problem is not always apparent from casual inspection. On a refurbishment project it is worth walking round the property carrying out a simple sketch plan of each floor to establish if chimney breasts appear in some positions but not at the corresponding level on another floor.
• Inspection the roof space. Sometimes there can still be a ton of masonry supported within the roof space but removed from above the roofline and beneath the top floor ceiling joists.
• Note: The opposite may be true: the formation of a chimney, flue and hearth may have effectively created a section of wall that is better supported than the lightweight foundations on the remainder of it. This can be a cause of differential settlement in the wall, so bear this in mind when inspecting to carry out repairs to other parts of the structure.

As with all building elements, pay careful attention to what has caused the problem you are attempting to fix. For example, when assessing distortion to the chimney, consider whether water may be penetrating and exacerbating the problem. (Frequently the cement flaunching smoothed around at the top of the stack to drain water away has cracked, allowing water to actually penetrate into the masonry. So, checking and repair of the flaunching condition is one of the first things to establish: this may require a long ladder inspection.)

The basics should serve as a useful aide memoire when you are out on a site inspection.