FAQs

The best way to alleviate problems caused by damp is to remove any damaging modern materials and replace them with lime. Lime is vapour permeable, which means that the excess moisture can leave the walls by the process of evaporation – just like hanging washing out to dry.

Every old house is individual and will have its own particular characteristics. There are so many elements which influence a buying decision. If you love an old house, it can be repaired when time and funds allow. TLC can help you plan this process with our Old House Reports.

In most cases, cement render traps excess moisture in solid walls. Cement is not vapour permeable, so moisture is unable to evaporate from its surface. Cement render is strong, yet brittle, which can cause it to crack when the house moves one way in the winter as the ground beneath it swells and the other way in the summer when it dries out. Lime is able to accommodate these movements.

Not necessarily. Most of the evaporation takes place through the outer skin of a solid wall. If there are weeks of sideways rain to endure, the moisture in the wall might saturate the inner core of the wall and reach the interior surfaces. If these surfaces are lime plastered and limewashed, the moisture will simply evaporate into the room.

Extensive repairs can be costly as they take time to do properly. However, doing the wrong thing by applying modern materials is much more expensive in the long run and will damage the investment in your home. The list of materials used in conservation work is usually much shorter than modern building, but the time taken is often longer as the works require care and sensitivity. We work with our clients to prioritise repairs and cut our cloth accordingly.

Lime finishes absorb carbon dioxide from the atmosphere. The process by which this happens slows and stops when the temperature dips below 5 degrees centigrade. Once the temperature rises above this, the process restarts. Over the past 20 years or so, we have experienced a distinct change in the climate of West Wales. Winters are becoming wetter, but warmer. The exterior lime season has extended and with careful protection using heavy gauge hessian sheets as protection, we can work outside into November. After this, interior works can be carried out until March. Of course, these dates are guidelines and the location and exposure of the building will make a difference to the timings too.

Sadly, we are often the bearers of bad news when someone has spent a great deal of time, effort and money coating their houses with “breathable” paints and renders. The key issue is whether these materials allow vapour to pass through them, not air. It is often possible to pass air though in laboratory tests, but in the extremely wet climate of West Wales, many of these products still trap moisture. To date, mankind has not invented anything as effective as lime in allowing moisture to evaporate from a solid wall as vapour.

There are a wide range of building limes and they produce a wonderful palette of materials to choose from. Lime is a natural product. It started life many millennia ago as sea creatures which expired and sank to the bottom of the ocean. Over time, these formed limestone which covers about a fifth of the planet today. When building limes are produced nowadays, the limestone is dug out of the ground and burnt in a kiln to produce quicklime. This can be used as is (in hot mixes for building for example) or water can be added to produce either a hydrate powder or a putty. The chemical make up of the limestone varies across the world. In Wales, the predominant limestone used in the production of lime contained aluminas and silicates. These impurities produce a chemical set which makes the lime more resistant to moisture initially. It then goes on to absorb Carbon Dioxide from the atmosphere as it carbonates over time. Eventually, chemically it returns to limestone.

Building limes are without doubt less harmful to the environment than modern cements. For a start, in their act of curing, they absorb carbon dioxide from the atmosphere. Of course, in their production they do the opposite – carbon dioxide is driven off the burning limestone rocks. The extent to which this becomes an issue environmentally depends on the way in which materials are produced – the scale, the temperature of the kilns, the materials used to fire these kilns, the environmental cost of the aggregates it is mixed with and the transport of these materials. The environmental cost on site should also be taken into consideration – lime scores highly when compared with cement on site where there is much less wastage. At the risk of this being the longest of the frequently asked questions, there is the whole lifetime of the building to consider. Correctly repaired and maintained solid walled buildings can last for generations, making them truly sustainable – unlike most modern new builds which are often designed to last as long as a mortgage.