Dampness in building elements

Internal plumbing

Kitchens, bathrooms and sanitary fittings, central heating circuits, water mains, and foul and waste pipework all are potential moisture sources.

  • Pipework joints may have failed and be leaking, particularly where connections involve different metals (bi-metallic corrosion).
  • Cold pipes, WC cisterns and other containers of cold water may be cold enough to enable condensation to form at their surfaces which then drips onto the floor or into a void.
  • Hidden voids containing pipework (e.g. behind bath panels, or ductwork concealing pipe runs) and pipes embedded in wall plasters or floor screeds are often the cause of damp problems.
  • WCs often leak at flush pipe connections, rotting timber flooring adjacent to the pan.
  • Careless use of WCs, baths or basins can cause spillages and wetting to the walls and floor.

Moisture generated in wet rooms such as bathrooms and kitchens can seriously damage plasterwork and timber ceiling joists above where water vapour is allowed to permeate through ceiling plasters, and can often degrade plasterboard linings to partition walls.

Baths without efficient overflows or poorly sealed tiling can cause considerable water damage to bathroom floor finishes, ceilings and decorations to rooms and areas below. Traditionally during a survey baths, basins and sinks are filled up and emptied to check for leaks, including a test of the overflows.

To check soil pipes, waste fittings, and pipework, first dry the pipework with absorbent tissue, then fill and empty baths, run taps and so on, and use a dry finger to search out leaks and drips. A sheet of cardboard or paper left for a time under suspect fittings could show up a drip. (See Testing water mains in Surveying equipment and tests.)

Figure 1: Pipework cluster as a result of new central heating and cold water storage tank installations to a multi-storey block of flats. The nightmare became a reality when one of the pipe joints failed to the 15mm copper pipe in the centre of the cluster causing water to penetrate through the ceiling of the top floor flat

Test central heating pipework

The central heating system in operation is, in effect, a 'live test'; water is in the pipes, and is being pumped around at pressure. Evidence of leaks from joints includes staining of ceiling plasters, drips and spreading wet patches in screeds or carpets. The tendency to hide pipes in horizontal or vertical ducts, or in screeds, makes locating leaks that much more difficult, because opening up ducts can be a very destructive operation.

 

If the central heating system incorporates a pressure dial (e.g. on the front of combination boilers) a pressure drop indicates that water has been lost from the system, although bear in mind that as the system cools down or heats up the pressure will change as a matter of course. A small leak may mean the central heating circuit needs topping up occasionally with extra water from the filling loop, whereas a more serious leak could mean topping up is needed much more regularly.

 

Pipework can be drained and air tested. This is time-consuming because of the need to drain down and refill the system, but it confirms whether or not the system leaks. If it is possible to pump the pipework up to a reasonable pressure, escaping air can be heard hissing from leaky joints, and suspect joints may be smeared with soapy water, which will produce bubbles where air is escaping.

 

Pipework leaks in screeds, inside floors, or deep inside ducts are not easy to locate. Pinpointing the leaks and determining how serious they are may involve compartmentalising the test - that is, isolating and testing the various parts of the circuit. It is more difficult to test a 2-pipe system in sections than a 1-pipe system, because the flow and return pipes are fed to each radiator from a 'tee' connection, probably situated under a floor or in a screed or duct. Such testing is very time consuming and therefore costly.

 

Floor hygrometers using a humidity box and hygrometer probe, a capacitance (radio frequency or search mode) to map the solid floor bearing buried potable water pipes can be useful in trying to identify a pattern of leakage. Thermal imaging cameras may also be very useful in mapping hot or cold spots in the floor to determine the likelihood of a water escape. Metal detectors are a useful addition to determine more precisely the location of any buried pipe in conjunction with the pattern and extent of dampness detected using the aforementioned equipment.