ASK THE EXPERT

Douglas Kent, technical and research director at the Society for the Protection of Ancient Buildings, answers your renovation queries

QSome of the soft red bricks in my 16th-century inglenook fireplace are crumbling. What should I do about it?

The faces of bricks in fireplaces can crumble (‘spall’) for a number of reasons. This may be, for example, because they have been cleaned aggressively, perhaps by sandblasting, or are suffering from a salt problem due to dampness after an impermeable floor has been laid nearby in place of an earlier breathable one.

In some cases, the best redress can be to apply to the bricks in question a proprietary mineral-based fluid penetrating solution designed to consolidate problematic surfaces while remaining vapour open. This comprises potassium silicate (waterglass) and should not be confused with other colourless treatments on the market, the use of which would be inadvisable in this context.

Where the bricks are damaged to such an extent that their faces have been lost, it may be feasible to undertake some localised repairs using a coloured mortar to build up the decayed areas. Skill is required, though, to achieve a good long-term colour match. In other instances, it may be possible to remove the bricks (especially if their joints have not been pointed in a modern cement mortar) and reverse them to hide the deterioration. Other approaches are to apply a lime plaster over the bricks where this is missing and there is evidence that it existed historically, or to insert matching new bricks.

Only bricks that are severely damaged should be cut out and replaced. Exact replication is very difficult, but there are a number of good suppliers producing new handmade bricks at reasonable prices. Replacement bricks should match the existing ones as closely as possible in size, colour, texture and durability. Q

What can I do to repair damaged timber stair balusters?

You can repair a long, diagonal split in a baluster by working in some PVA and carefully attaching a clamp while this sets. A broken baluster might need dowelling and gluing back together in a workshop. If loose, a baluster can be resecured with glue and a countersunk woodscrew fixed diagonally through the end into the handrail or string.

If you have a question for Douglas, email it to periodliving@futurenet.com*