One of our Surrey building surveyors carried out a building survey for a Edwardian cottage, in which there was an extensive amount of dampness. We tested for damp (which we do in all building surveys Surrey) and assessed the property for repair. There was also another significant defect in rotten timber windows in which there was evidence of wood boring insects.
Dampness in Edwardian cottage
We noted extensive areas of significant dampness to the internal areas of the Edwardian cottage at the time of our inspection. We are informed that this is due to a leak in the roof void. We could not confirm this at the time of inspection as this was obscured and blocked by the water tanks. However, we can confirm that the damp is unlikely to come from a leak to the roof as there is sarking felt which would prevent most damp penetration. The roof, although not in great condition, is not in bad enough condition to allow for this amount of moisture ingress.
Extensive damp was found, on the ground floor, in the entrance hallway, the sitting room (most notably around the chimney and the front elevation external wall) of the Edwardian cottage. Extensive damp was found in the second and third bedrooms on the right after you climb the stairs, in the cupboard in the first bedroom and in the landing from the cupboard to the end of the hallway onwards. In these areas the majority of walls and ceilings were damp. The finishes in these areas were in bad condition at the time of inspection, however the true extent of the damage will only be clear once the damp has dried.
Normally the rule of thumb when it comes to drying out a building is that it takes a month for each inch (25mm) in width of wall that needs to be dried. With a 240mm wall this would take 9.6 months to dry out completely if it is fully saturated. This does not mean that it cannot be inhabited, just that damp problems may reoccur for this period. Damp will remain within the building fabric even if it is dry on the surface.
There are normally two methods of drying out a building, such as this Edwardian cottage. These are using the heating system, fans and heating. This relies on good ventilation (opening all the windows) and heating to evaporate the moisture from the building fabric. The other method, which could be seen in this Edwardian cottage, is using dehumidifiers. When using this method, it is important to seal the house otherwise you tend to extract moisture from air entering the house from the outside rather than that of the building fabric. Seal over the WC, Windows, Fireplaces, wastes and seal overflows and air vents/ extractor fans.
The existing plaster may be left in place until the drying is complete as salts from water may collect on the plaster. The more the walls are dried, the more salts will accumulate. Any new plaster will accumulate these salts and potentially be damp for a longer period. If this is not possible it is recommended that a permeable plaster is used rather than gypsum. The best option would be a cement-lime-sand plaster which would allow the wall to breath.
Particular attention during the drying out process should be given to the timbers. Wet timbers are prone to rot and insect attack. Wet rot tends to affect timbers with a moisture content of 50%. Particular attention should be given to checking for dry rot with affects timbers with a content of 20-30% and has been found after leaks have occurred during the drying process. All timbers should be checked for rot by a reputable damp and timber specialist. When timber dries it can also warp and distort and may need to be replaced when the drying process has been completed.
Surrey building surveyor spots timber rot and insect attack
There was evidence of both wood rot and insect attack in some of the window frames of the Edwardian cottage. This was most notably found in double glazed fixed pane windows in the kitchen.
There are two main types of rot, dry rot and wet rot. Wet rot is a blanket definition for a number of different fungi. The main way that they can be told from dry rot is the moisture content of the timber, wet rots only grow in saturated conditions.
Dry rot wood will become dry and crumbly and tends to like still damp air, areas where it is in Contact with damp brickwork and where ventilation is poor. The Fungus mycelium can be identified by cotton wool, bright lemon patches or a thin leathery skin may appear. These strands can move over masonry and older plaster which has lost its alkalinity, effectively breaching party walls. The wood will become dry and crumbly, there will be cuboid cracking, a leathery appearance.
When identifying the type of insect attack it is important to look at the frass (excretions) of the insects, the size of the boreholes and the condition and type of wood which has been affected.
In the windows as seen above the bore diameter was around 1-2mm and the frass was of a brown powdery type. However, we can only confirm the presence of insect attack if we find the actual insects. Due the life cycle of insects this is very difficult to ascertain. We would also have to remove the wood to see what is inside it. As our surveys are non-invasive we could not do this.
This shows the importance of keeping wooden framed windows well decorated at all times. The cost of decoration is small compared to the cost and disruption caused from replacing the windows especially with like for like. Replacements will have to be redecorated anyway unless uPVC is used which has a shorter lifespan and shouldn’t (sometimes can’t) be used in period properties such as these. If decorated well and often wooden windows can last in excess of 100 years. Some Victorian windows that have been well looked after are still in good condition. the windows above are substantially newer and have been left undecorated meaning that wood boring insects and rot could get into the wood.
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