Ask the expert
Douglas Kent, technical and research director at the Society for the Protection of Ancient Buildings (SPAB), answers your renovation queries
Q What is the best method for removing old putty from windows
Window putty may have to be removed where it is failing and could cause the timber below to rot or where glazing must be removed to enable repairs to a window frame. Putty may sometimes have deteriorated to such a degree that it can be taken out by hand. Otherwise, an organic paint stripper, soldering iron or bespoke infrared lamp can be used to soften the putty. Other methods of softening include the application of household bleach or a mixture of potassium carbonate and quicklime in a 1:3 ratio (by weight). In all cases, great care and patience are needed because numerous applications may be required to soften the putty sufficiently.
Q Our converted old coal cellar has become quite damp. How should we deal with this?
One approach often used to overcome dampness in cellars is to use a proprietary ventilated dry lining under a new finish (such as plaster or screed). The lining comprises a studded membrane fitted to the internal faces of walls and, if required, floor. The air gap behind the membrane allows the dissipation of moisture coming through the building and can be drained. This might necessitate forming a sump that can be kept dry by means of a float-operated electric pump, which needs to be regularly checked and maintained to ensure it is operative. This method is far more reliable than traditional tanking, which tends to be expensive and depends upon faultless workmanship.
Q We are replacing some inappropriate plastic rainwater downpipes which serve parapet gutters on our old house with cast-iron guttering. Do you have any tips?
Water from a parapet gutter collects in a sump from where it is discharged through the wall via a pipe (traditionally of lead) into a hopper head at the top of the downpipe. Hopper heads are prone to becoming blocked with leaves and other debris so I would recommend you incorporate an overflow pipe to minimise the risk of damage to roof timbers below