A large portion of older buildings, such as Georgian and Victorian houses, were designed in a way to be breathable.
Lime mortar and clay bricks were very popular in the Georgian and Victorian periods. These materials are permeable by nature, meaning when the water hits the external envelope can be absorbed and evaporated.
Combined with the use of lime products used in interior plasterwork, suspended timber floors and timber framed windows, ventilation would be at a good level to prevent condensation and damp build up and keep the relative humidity levels at an acceptable standard.
Always when redecorating or refurbishing an older home, it is best to use materials matched to the existing properties of the house.
1. Cracking, open joints, spalling brickwork
Over time, no doubt hairline cracks or open joints are bound to appear especially on the southern facing elevations due to thermal expansion and contraction. These can easily be infilled with a lime-based mortar, for a quick fix.
Spalling brickwork can also occur when the mortar bond is too strong, therefore the brickwork will crumble.
A general rule of thumb is that a mortar bond needs to be weaker than the brickwork that it is surrounding. With lime mortars, these are flexible and can adapt to natural movements from expansion and contraction in the walls without cracking.
2. Dampness in walls
Dampness in walls can be caused by several things, which can combine. This will make a diagnosis hard in many cases. The most common causes are condensation, interstitial condensation, penetrating damp, leaking services, bridging of the damp proof course and raised ground levels.
Condensation will occur when there is a build up of vapour inside a room of a house where the walls are colder than the vapour in the air. The warmer the air is, the more vapour it can hold.
4. Interstitial condensation
Interstitial condensation happens when warm air penetrates the envelope of the building. This vapour will condensate when the dew point is reached, and water droplets will form. This can occur in older Victorian and Georgian housing if they are furbished with gypsum/cement-based materials. For example, as warm air flows from warm to cold, this warm vapour will permeate through the building. As brickwork is generally porous, it will absorb this moisture and allow it to be released into the atmosphere. If, for example, a cement based render has been used, this would prevent the release of that moisture, causing interstitial condensation.
The older the materials on the building are, the more likely it is they allow for penetrating dampness. This can be from a variety of sources, such as cracked tiles and open mortar joints to incorrect detailing.
6. Bridging of the DPC
Damp proof courses were introduced in construction in the 1800s. These were traditionally either impervious bricks, slates or lead. These were incorporated to prevent damp rising up the walls. Typically in these types of buildings, our Kingston Surveyors have witnessed DPC bridging in simple ways such as the ground levels being too high.
This means moisture absorbed by the ground is coming into direct contact with the porous bricks, causing symptoms of damp to the internal face of the property.
Blocked Air bricks/vents
As floors in this period often employ suspended floors with a flood void, an air circulation is required underneath to ventilate and keep the humidity levels low, to prevent the timbers from rotting.
We have noted on several properties that the vents are either blocked with debris, or the ground levels have risen which restricts the ventilation flow. The air bricks and vents can also be incorrectly detailed at times, not providing enough flow of air through the gaps.
If the air bricks or vents aren’t allowing that circulation of air, then moisture will be allowed to settle on the timbers.
Similarly, chimneys that have been blocked off will also need to be vented for this same reason.
Many of these Georgian and Victorian houses had roofs with clay tiles originally. Occasionally, when clay tiles are replaced with heavier (concrete) tiles, this can cause some major problems. For example, roof spread can occur, where the original timbers and roof structure is not designed to hold that excess weight. Walls can push out of vertical, and a chain reaction of defects can be caused.
Older houses, such as Georgian and Victorian, were generally not constructed using mathematics, just by the tradesman knowledge. Over time, timbers in the buildings such as lintels or even purlins, can deflect over time due to the loads implied upon them over the long term. A range of remedial methods is available in this case and is not always as daunting as it sounds.
Particularly in Georgian buildings, drainage problems are very common. This can be due to the way the roof is designed; in many properties, the guttering is hidden from view behind parapet walls and connected to cast iron downpipes. A guttering problem can be easily ignored in these cases, apart from where rust is obviously spotted.
Our Surrey surveyors have witnessed penetrating dampness that has occurred due to incorrect rainwater disposal of even refurbished uPVC downpipes in Victorian buildings that have lead to a pool of water being formed behind a parapet wall, which eventually leads to rainwater ingress and damp patches on ceilings. This defect is often latent until discovered, and in some cases, the damage has already been done.
Heave / subsidence
Although not as common, this can be an issue as the foundations are generally very shallow. Removal of a tree near shallow foundations can cause heave, or the existence of a tree near a shallow foundation can cause subsidence.