Frequently Asked Questions

What is a traditional building?
How should traditional buildings be repaired?
Why Use Lime?
What Lime to Use?
How can damp be prevented?
But wouldn’t a proper waterproof render prevent water getting in?
So why do bank and building society surveyors require injection damp proof courses as a mortgage condition?
Is damp the only problem caused by using modern materials on an old building?
What can be done if modern materials have been used on a traditional building?
Aren’t traditional materials much more expensive?
What about the environment?
Where do I obtain traditional materials?
What if I need advice?
Do you run any training courses either for owners or tradesmen?

What is a traditional building?

The term ‘traditional building’ describes buildings which were constructed before about 1900 with solid walls, shallow foundations and, before 1875, no damp proof course. The soft lime mortar and plaster gave the buildings flexibility to move on their shallow foundations without causing permanent cracking. The use of stone, soft bricks, clay and timber with permeable lime mortar and limewash allows the buildings to ‘breathe’ and thus avoid damp problems.

How should traditional buildings be repaired?

Repairing an old building using modern materials creates problems, in particular re-pointing or rendering with cement and trying to keep out damp with waterproof coatings. Traditional lime mortars and plasters preserve breathability and flexibility. They prevent frost, water and salt damage to masonry, damp in plasterwork and floors and rot in timbers.

Repairs and decoration using traditional, natural materials also look better and are more in keeping with the traditional appearance. The finishes have soft variations and the colours a natural subtlety that cannot be achieved artificially.

Why Use Lime?

Lime has been used in mortars, plasters, renders and paints for centuries. It was continuously used in building work from Roman times up until the 20th Century. It is only in the last few decades, particularly since the 2nd World War, with the development of Portland cement that lime products have ceased to be used. Lime mortars, renders, plasters and limewashes have many properties that have encouraged a healthy resurgence in their everyday use:

they are porous and absorb moisture from the surrounding bricks or stones; any salt or frost damage occurs in the lime, thus protecting the surrounding materials
they allow walls to 'breathe'; moisture will evaporate as rapidly as it enters (whereas most modern mortars and paints hold moisture in the wall)
they are relatively flexible and will accommodate some movement in a wall; if they crack they will 'self-heal' when exposed to air
they are 'soft on the eye' and compliment the beauty of other natural and traditional materials
they are considered to be more environmentally-friendly than conventional materials
they allow building materials (eg stone, brick) to be re-used, cement is so hard that we will be unable to reclaim much of the stone used today.

What Lime to Use?

It is important that the most appropriate material for the well-being of the building is chosen. Every situation needs to be carefully assessed in terms of:

softness of stone, brick etc - this should be a major factor in selection; the mortar should always be 'softer' than the stone/brick because it is the 'sacrificial' element designed to take water away from the main fabric of the building
the environmental conditions - where the environment is very wet (eg sea-defence walls, canal walls) a hydraulic lime is more appropriate because of its ability to set under water
the existing materials; repairing like-with-like will usually provide the most satisfactory solution both aesthetically and technically, but it should not be done without considering the performance of the original materials
the time of year - lime work (like cement) should never be done when the temperature is 5oC and falling; ideally, fat lime work should be done in spring / early summer, otherwise consideration should be given to adding a pozzolan (brickdust, calcinced clay etc) to a fat lime to speed up carbonation or to using a hydraulic lime (eg in very wet conditions)
the available time - occasionally work is programmed with insufficient time to support the use of the materials specified; rapid builds necessitate rapid sets in which case consideration should be given to adding a pozzolan to a fat lime or to using a hydraulic lime.

Frequently, the choice still seems to be based on the availability, or lack of availability, of skills, which means that cement is often introduced into buildings where it has no place and will - in the long term - almost certainly damage the very fabric of the building. There is nothing 'magic' about using the basic lime-based materials - mortars, plasters and limewashes but there are specific rules which will ensure the right result - the materials are often blamed despite the fact they have been used pretty much continually for 1000s of years and structures and parts of structures such as the Great Wall of China have survived. Fat Lime Putty or Non-Hydraulic Lime is produced by slaking fresh Quicklime (Lump Lime) in an excess of water which is then left to mature. The resulting fat lime putty is also known as non-hydraulic lime because it requires exposure to air to carbonate and does not set under water. This lime is often regarded as the most appropriate lime to use in the conservation of old buildings where maximum permeability is required. Fat Lime Putty is blended with sand to produce plasters and mortars or can be diluted to make limewash.

How can damp be prevented?

There is a common misconception that damp is usually ‘rising damp’ caused by the absence of a damp proof course. This is almost never the case in a traditional building where damp is normally a symptom of some other problem. Things to look for are:

Faulty gutters, down-pipes or drains. The Society for the Protection of Ancient Buildings in a review of its technical advisory service found that these were the cause of over 80% of damp problems
Raised ground levels against external walls so that damp seeps through from the earth outside
Repairs that have been made using modern cement pointing and render and wall coatings using modern impermeable paints. This traps water which then builds up internally and externally as damp patches and causes ‘bubbling’ on the surface.

But wouldn’t a proper waterproof render prevent water getting in?

This is impossible to achieve with any type of building, whether traditional or modern. Apart from moisture getting in from outside, much is generated internally by people cooking, bathing, showering and so on. Whereas modern buildings need vents installed to deal with this moisture, the construction materials of traditional buildings absorb excess moisture from the atmosphere and then release it when the air is drier. For example, a bathroom with lime plaster and a breathable wall finish suffers from virtually no condensation.

So why do bank and building society surveyors require injection damp proof courses as a mortgage condition?

Most building society surveyors understand only modern building techniques and do not appreciate the dynamics of a traditional building. They will often make it a condition of the mortgage that a survey is undertaken by a member of ‘The British Wood Preserving and Damp-proofing Association’. This is a trade organisation of companies who are in business to install damp proof courses and they invariably recommend their own product. The treatment is, at best, unnecessary, often ineffective and can create new damp problems. If moisture is prevented from evaporating from walls, there will be a bigger concentration elsewhere, typically in solid floors.

Is damp the only problem caused by using modern materials on an old building?

No. A very common and serious concern is that the surface of bricks and stone crumble and flake away if hard cement mortar is used for repointing. It looks neat and smart when it has just been done, but damage to the brick or stone starts soon after.

What can be done if modern materials have been used on a traditional building?

Ideally they should be replaced, but it is normally neither possible nor cost effective simply to remove all the modern materials and replace them with traditional materials. But here are some suggestions:

Re-pointing. When re-pointing is required, use a soft lime mortar, not cement. If cement mortar is creating damp problems or is causing the masonry to crumble, consider removing the cement pointing if this can be achieved without damage to the masonry. If damage would be caused, it is best to leave until the cement pointing becomes loose.
Render. If a cement render has been applied, remove it and leave the original masonry exposed or re-render using a lime mortar
Redecoration. If possible remove vinyl type paints and wall coverings and replace with breathable and natural materials. Not only will these help to preserve the fabric of the building but will also improve the living conditions through better moisture control and a reduction of toxic fumes.
Damp patches. If walls contain damp patches, this may coincide with the use of modern gypsum plaster for repairs. If so remove the modern plaster and replacing with lime plaster

Aren’t traditional materials much more expensive?

That depends:

Re-pointing using a lime mortar will cost very little more than cement, because although lime is more expensive than cement, the amount of material used is very small and the labour costs will be similar.
Repairs carried out using like-for-like traditional materials, for instance internal plaster, can avoid a much bigger job of completely stripping and re-plastering.
Over all costs of materials tend to be higher, but repairs and restoration will last longer and avoid creating new problems by preserving the old building’s breathability and flexibility, reducing damp problems and giving a healthier living environment.

What about the environment?

Lime is also better for the environment – drier walls mean lower heating bills and masonry built with lime mortar can be re-used, which is not possible with cement mortar.

Global warming is increasingly becoming recognised as a serious problem. The construction industry together with the occupation and maintenance of buildings is responsible for 50% of CO2 emissions in the UK (source – Sustainable Buildings Task Group).

The use of lime as a binder in mortars and plasters instead of cement reduces CO2 emissions. Not only is less CO2 released in making lime compared with cement but also lime mortar reabsorbs CO2 (through carbonation) as part of the process of setting.

Retaining old buildings by repairing them properly with traditional materials, reduces energy consumption and creates a better living environment. A recent RICS report showed that 25% of the UK’s housing stock has toxic mould resulting from the inability of buildings to dry out. This would be helped by the use of natural, breathable materials.

Masonry constructed with lime mortar is also recyclable, due to lime mortar being relatively soft, whereas that constructed with cement mortar cannot.

By making these materials more readily available and promoting their use, more old buildings will be saved and new buildings will be better to live in, and will consume less energy and reduce greenhouse gases in their construction and operation.

Where do I obtain traditional materials?

Go to Products

What if I need advice?

We are always happy to deal with queries by email or phone

info@ingarsbyconservation.co.uk [can this be non case sensitive?]

We also provide an advisory and project management service and can recommend craftsmen, tradesmen and professionals such as architects, surveyors and engineers.

Do you run any training courses either for owners or tradesmen?

Not at present, but we intend to in the future. In the meantime we can recommend suitable courses run by other organisations. See page Links page for details.