Damp investigations

Figure 1: Saturated section of partition wall where staircase abuts. High moisture levels where the timber string of the stairs is in contact with the wall. The cause of the dampness was first thought to have been due to the lack of a tile splashback and mastic joint behind the kitchen sink unit on the other side of the partition wall. The actual cause was water leaking from a burst water main adjacent to the property which saturated the solid floor in the kitchen under the linoleum floor covering

Figure 2: Sections of perforated, zinc-coated, steel 'barrel', potable water main supply pipe. These sections of pipe were located just outside a 1920s cottage in London where the pipe had been laid into the ground at a depth of approximately 750mm. The steel pipe had been laid without any protection other than the zinc coating. Zinc is a sacrificial anode and will, in aggressive soil, eventually break down, enabling the steel pipe to perforate causing a waste of water

Figure 3: Blue detergent water in a blocked back inlet gully. The cast-iron pipe takes waste water from the bathroom into a hopper at the head of the pipe. Nowadays the pipe would be let below the cover grill of the gully or connected directly to the branch drain. Regular clearance of external gullies is necessary to prevent leaf litter and airborne detritus causing blockages. Pre-formed cover guards can be installed to prevent blockages from blown material, abuse or accident

Figure 4: Effects of a long-term waste of water problem from a discharging overflow pipe. Green algae and white efflorescence on the face of the wall is a typical signature of prolonged saturation of the masonry. Water had penetrated the solid wall into the habitable space above the horizontal dpc. This frame indicates the importance of external observations in relation to internal dampness

Figure 5: Extensive damage to a brick built chimney stack. Lightning had struck the stepped lead, apron flashings around the base of the stack and transferred down through the lead valley gutter, splitting the gutter through most of its length. The collapsed masonry fell through the tiled apex roof, damaging the ceiling in one of the upper bedrooms. Luckily no one was injured. Heavy rain from the storm ensured that copious amounts of rainwater entered the upper rooms of the building causing widespread damage

Figure 6: A former Victorian single dwelling converted into 3 separate flats. The overflow pipes were routed from the bathroom out over the window areas. The thinking behind the routing of most overflow pipes is to position the end of the pipe externally in a location likely to cause inconvenience so that occupants of the building raise the alarm when a waste of water occurs. In this case the flats were unoccupied: there was no one either at home or with any interest to raise the alarm. Landlords and building owners alike should consider as far as is practicable the reduction in stored water within empty dwellings – although electronic warning devices exist that can remotely alert the owners to a problem. The alternative is to drain water tanks and turn off water isolation valves. The damage caused to the upper flats in this case resulted in thousands of pounds of remedial works to repair rotted timber windows, internal replastering, damaged timber floorboards, joist ends, skirting boards and ceiling damage (not to mention redecoration). All for the price of a couple of defective ball valves.

Figure 7: Severe condensation on the kitchen ceiling of this basic dwelling. High occupation, under-heating, the use of liquid based fuel heaters, the drying of clothes internally, lack of adequate ventilation or thermal insulation, and poor design (bathroom leading off the kitchen to the ground floor) all contributed to this problem. The occupants were found to be in severe fuel poverty

Figure 8: Front elevation of a period property in Brighton on the English south coast. The deterioration of the paintwork, cast-iron balustrade and metal rainwater pipes is common in marine residences. The aggressive atmosphere around coastal locations is due to the high chloride content resulting from the presence of sea water. The chloride-rich salt water and wind-blown rain, from prevailing westerly Atlantic air systems, present huge challenges for the maintenance and protection of buildings from water ingress, corrosion and degradation. Some of the earliest examples of cavity walls can be found in coastal towns – as part of the early builder’s primary defence against water ingress into the habitable space as well as a method of thermal insulation

Figure 9: Timber suspended floor in the kitchen of a Victorian end of terrace property. The timber floor was subjected to the effects of dry rot caused by a leaking lead water main laid under the suspended floor on the oversite. It is common in Victorian properties to find original lead water mains laid under suspended floors and routed to kitchens at the rear. Over the years, previous owners had built up the external path and patio, raising the ground levels and blocking the perimeter wall subfloor air vents as well as bridging the horizontal physical dpc in the walls. The leaky water main was hydrating the under-floor area. This became an ideal environment for dry rot which proliferated, causing widespread damage and the eventual collapse of the timber floor

Figure 10: Black circles evident on a ground floor in a tenement block (c1900). The pattern of black staining is consistent with the locations of ferrous nail fixings. The timber floors had been laid directly onto a clinker ash substrate coated with pitch tar acting as a damp-proof membrane. Over a considerable period of time ground moisture had gradually been introduced into the timber boards from each corroding nail fixing. Naturally the process of wet rot to the timbers would speed up considerably if linoleum or foam-backed carpet was overlaid on the floorboards. This problem can be found up and down the country in many properties built in the 1920s

Figure 11: A classic case of bridging of the horizontal dpc at a solid bay wall in a Victorian property built around 1900. Successive owners of the property have built up the abutting external ground levels. Note the location of the through wall subfloor air vents. Rainwater had penetrated through the vents causing localised flooding of the internal subfloor oversite resulting in a severe damp problem internally at the living room wall. Wet rot of the internal subfloor timbers was also in evidence

Figure 12: The grassy bank and stone wall abutting the rear elevation solid wall to the back addition of a late Victorian property was clearly causing bridging of the horizontal dpc at the wall, leading to a severe internal damp penetration problem

Figure 16: Leaking overflow pipes – cause of slime mould internally

Figure 17: Green slime mould in kitchen (internal wall at abutment to external solid wall) caused by leaking overflow

Figure 18: External solid wall of an early Victorian property where the remedy to cure the dampness internally was to insert a series of retrofit clay or ceramic tubes into the wall to help dissipate the moisture. The inserted tubes have been placed at height above the internal floor level

Figure 19: Brown water staining caused by blockages within the chimney cavity. This was due to fallen rubble and flaunching from the chimney stack above the roof enabling rainwater ingress into the chimney cavity affecting the top floor bedroom