It is seldom possible to make conclusive inspections of the timbers of ancient timber-framed buildings because the surrounding or in-filling fabric covers a greater part of their surface. Main structural members such as corner posts and horizontal plates, which carry roof and first floors, are often completely hidden, especially at the bearing ends which are most subject to insect and fungal attack.

Construction of upper floors frequently prevents access to the undersides of floorboards - where joists or beams are exposed in the ceiling below, ceiling materials are often fixed directly to the undersides of the floorboards. In other cases, the original floorboards may be covered by a second layer. It is common to find insulation materials under the floorboards and between joists.

Use of wooden ground floors was not usual until the 19th century, up until then earth or bricks were used. Where wooden floors have been added, ventilation is likely to be inadequate, and joists have often been laid on the earth. The floors are prone to fungal decay, and may require replacement or extensive repair and excavation work.

When extensive renovation has been carried out on a building, it is even more difficult to assess the condition of the timbers, because the more obvious defects may have been removed and others covered by elaborate and often expensive decoration. Timbers exposed internally have often received a decorative finish that seals them and makes insecticide treatment impossible without removal of the finish.

Timber framed houses present many difficulties in detecting and eliminating dampness. The majority were built prior to 1900 and do not normally have a damp-proof course. It can be expected that rising dampness will be occurring at the base of most houses of this type, often causing the sole plate, i.e. the base plate of the timber frame, to decay. Often the timber framework is rendered externally and plastered internally, possibly more recently using sand/cement, which often makes testing with an electrical moisture detection meter inconclusive. Even when dampness is visible or can be found by the use of a moisture meter, there may be no masonry base suitable for injecting a chemical damp-proof course, due to the floor or ground level being up to or above the sole plate.

If the walls have insufficient masonry base, or where the external or internal level is at or above the sole plate and cannot be lowered, it will be necessary for a physical damp-proof course to be installed by a local builder using traditional methods.