Key Causes of Damp within Old Buildings. Content. 1 The cause of dampness. Tracing the cause. Rain penetration.
Rising damp. 5 Condensation. Internal wall treatment There are several ways in which the decay and damage of the fabric of an old building can generate excessive dampness. Waters carrying impurities may rise up from the soil into the building or driving rain or snow may penetrate through hairline cracks on rendered walls or through decayed brickwork. Excessive dampness encourages the growth of wood- rotting Fungi, the infestation of wood- boring insects and the corrosion of Metals. It can damage the contents of a building, the decoration and the furniture. Most importantly excessive dampness inside buildings can be harmful to the occupants’ health, and therefore must be prevented or treated. The cause of dampness.
Most traditional buildings absorb moisture and are porous to a certain degree. Roof timbers can on average maintain up to 1. This increase is generally caused by leaks, condensation or damp masonry.
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Most old buildings have solid walls, no damp proof courses and no felt under tiles or slates. Driving Rain can therefore penetrate the fabric of the building and rising damp can also enter into the building. Traditional building material such as stone, soft brick, lime- wash, lime based mortars and plasters absorb more water than modern day building materials but these traditional building materials have the advantage of allowing moisture to evaporate during drier conditions. Traditional living generated small quantities of water vapour.
Damp patch after rain (picture) In my home (includes DIY) MoneySaving. Do you have photos of guttering and wall area by damp patch's outside? There are more questions than answers. May go silent for unfriendly. Typically a damp patch will continually appear on a wall after rain. Symptoms appear as localized dampness in linear or patch form or widespread dampness which is highlighted on the lower sections of internal. Rain penetration in cavity construction. This typical symptom of this type of problem is a damp patch which continually appears on a wall after rain. If your damp wall is on or.
Before central heating was commonplace, open fireplaces would heat buildings. The open fireplace would draw large quantities of air through windows and doors, evaporating moisture from porous internal walls and the draw of air would remove moisture from timbers. Today’s requirement for comfort and for warmth has meant that we have seen a reduction in ventilation, and with modern materials and decoration can in turn trap moisture in old buildings. Central heating when first started up after summer months can draw soluble salts to the wall surface which then crystallize causing efflorescence. Therefore the heating should be started up gradually, at lowest levels to allow the building to acclimatize. In traditional buildings felt tends not to have been used under tiles or slates, and therefore if gaps occur or slates are missing, cracked or displaced, rain and snow can be driven into the roof- space. The abutment of a chimney or parapet to a roof is a vulnerable junction especially if a cement mortar has been used rather than a lead flashing.
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However, on occasions fillets of properly gauged lime mortar have been used successfully. The free flow of water in gutters is essential to prevent leakage or overflow. All leaves, moss and dirt should regularly be removed from gutters. Leakage from parapet gutters is particularly serious, as the space beneath tends to be warm, unventilated and contains the bearings of the roof trusses. Penetration can create Dry Rot, which has been the cause of the destruction of many old building. All down pipes should be clear of obstructions as blockages can create backups and then spill out at the joints. If prolonged wetting occurs, this can lead to damp patches and growth of moss, which will then retain moisture.
The brown stain appeared after heavy rain and other small areas are. Damp wall - what's causing it? Certainly if it appears after rain then I too would agree it. So despite the heat and there being a radiator directly next to the damp patch this hasn't dried the wall. What is Penetrating Damp? Other paths through which rain can cross through a cavity wall include incorrectly positioned wall. It is possible for damp to move within walls but this horizontal movement. Any tiny leaks from plumbing can be the cause of a large intense damp patch - the leaks.
Traditional Stone walls are generally porous and when set in a lime mortar of equal porosity slowly absorb the falling water, but if the wall has sufficient thickness then the wall will retain the water and draw it back to the surface to evaporate when the rains have stopped. If however the walls are not thick enough or the joints are weak or damaged then a lime based render would be used to protect and cover the walls. Modern renders made with cement are brittle and have a tendency to crack with the buildings natural movement or with variations in climate and therefore create cracks that allow rain fall to penetrate easily but find difficult to escape by evaporation. The build may therefore find its way into the internal face of a wall or even blow the external reader leading to further exposure and potential damage. Rising Damp. If a porous walling material such as Stone or brick is placed directly onto the damp soil, moisture will be drawn into it, this is called Capillary action. The absorbed moisture will rise into the wall to a height where there is a balance between the rate of evaporation and the rate it can be drawn up by the Capillary forces, the height will vary depending on the time of the year and the height of the water table of the soil.
Prior to the Public Health Act of 1. Traditionally where Flagstones or bricks were directly placed directly onto the soil to create floors the moisture that would rise through would be carried away with ventilation. Therefore any impervious covering such as a vinyl floor will trap in the moisture and become soaking wet underneath. The same with walls, any attempt to seal the walls with moisture barriers or impermeable paints or dense plaster renders will only act to push the damp further up the wall. Rising Damp contains salts carried up from the soil or found in the walling materials. Some salts are hygroscopic i.
The amount is limited but it increases with temperature. As air is warmed it will absorb more moisture but if air is cooled to a certain point below dew- point the air will revert to water. If any surface within a building is below dew- point it will cool the air next to it, and will cause condensation.
Condensation is dependent upon the temperature of surfaces and the humidity of the surrounding air. Many old buildings are difficult or expensive to heat due to the internal cold surfaces through dampness or poor insulation.
If ventilation is reduced in an attempt to conserve warmth, the air humidity inside will increase by the evaporation of rising damp or domestic activities such as cooking, washing up, drying clothes and bathing. Any surface, which is below the dew- point, will become damp by condensation.
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Condensation can occur in old buildings with thick walls such as churches if the building is heated intermittently and the air is warmed before the surfaces have risen above dew- point. Chimney flues can become damp through condensation. Modern boilers and closed stoves draw considerably less air through than open fires. Warm rising gasses may condense on a part of the flue, which is exposed or has a poor thermal insulation. The result maybe, deposits being carried through the brickwork and leaving stains on the internal wallpaper or plaster. Tracing the cause of damp.“The incorrect diagnosis of a damp problem may lead to unnecessary and expensive .
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Such as a high level of salts in the plaster- work but maybe the underlying masonry may not be damp. Results should be treated with caution and an ongoing monitoring of the situation would give a true picture of cause and effect.
Check Roofs, Parapets, gutters and down- pipes- Check exposed horizontal surfaces – areas that are likely to collect water.- Water leaks – these may run down rafters or the underside of the roof to appear inside the building some distance away.- Damp patch on ceilings – is this due to a roof leak, dripping condensation or both.- Roof space – ideally examine the roof- space during a period of wind and rain.- Rainwater disposal system - ideally examine during heavy rainfall. Systems may appear to deal with average rainfall but can fail under heavy or prolonged periods of rain. Walls- External wall surfaces should be carefully examined.- Attention should be paid to the pointing.
Is it traditional lime mortar or a modern cementitious mortar that may allow for water penetration through hairline cracks.- Parapet Joints – these can be very vulnerable especially if not covered with sheet lead.- Check, are there any water supply pipes that may have been embedded in walls and may have failed.- Rain penetration – these may produce defined damp patches on South or west facing walls and may evaporate after a few days then reappear following a period of heavy rain. Contaminating salts may be seen as a white deposits or feathery crystals. Mould growth would usually suggest condensation.- Dampness due to condensation – Usually found in patches. Beads of moisture on hard shiny surfaces or growths of mould on wallpaper, plaster or paintwork. Usually intermittent and independent of rainy weather.
Controlling rain penetration. Roof Repair. Roof tiles or slates may become cracked or move as a result of rotten fixings or movement in the building. Individual roof tiles or slates can be replaced, but during the life of any roof it will be required to be stripped and recovered.
Underfelting is useful but may be inappropriate for some old roofs, particularly under thatch. If it is used, it is essential that the roof space be provided with additional ventilation. Counter battens will be required for certain types of stone tiles and slate.
Modern mastics or resins should not be used in an attempt to seal a roof or secure the covering as these have been known to fail quickly and damage the covering to such an extent as to preclude the reuse of the roof covering in the traditional manner. Systems developed over recent years include rubber, polyester, urethane and polyisocyanate foams sprayed onto the underside of slates and tiles, may restrict the ventilation of the roof timbers, which could restrict evaporation of moisture and encourage decay. A competent builder who is experienced in this type of conservation work should carry out the repair of an old roof.
Contact Taliesin Conservation to discuss your project. Maintenance of gutters and downpipes and protection of walls. Gutters and downpipes should be cleaned and inspected at regular intervals. If there are any damaged cornices, string courses or other projections designed to throw water away from the building they will need to be repaired or reinstated.