Traditional Building Repairs

“Promoting sustainable, effective building maintenance”

At Cumbria Stone Walling, I provide repair and maintenance services for traditionally-built solid wall buildings. The following page covers some of the more common problems that home-owners are likely to face.

lime mortared repair to eroding red sandstone near Appleby-in-Westmorland, Cumbria

↣ Eroding red sandstone is a common problem in the Eden Valley. Non-hydraulic lime mortars will prevent erosion, but any significant areas of exposed stone remain vulnerable. Fully protecting this building would require a fundamental change to its appearance.

Basic Construction

Most traditional buildings in Cumbria and the Westmorland and Yorkshire Dales are rubble built stone buildings with basic detailing and a range of normally stone roof coverings. They are not complex in their construction and shouldn’t require modern materials in order to make perfectly comfortable modern homes.

The construction of solid wall buildings is essentially the same as that of dry stone structures, but with the addition of mortar. Two faces are built up and supported in the centre with stones and mortar; through-stones are usually incorporated at regular intervals to distribute the weight and accommodate seasonal movement. Strength is provided by the wall’s thickness (usually 2’ to 2’9”) and the load-bearing capacity of stone-on-stone contact. The mortars themselves don’t contribute significantly to the strength of the wall, but are vital in terms of durability and maintaining a dry environment within.

So long as the roof is in good condition and the walls well maintained, the ‘breathable’ nature of traditional buildings eliminates the need for modern ‘damp-proofing’ measures.

Tip: Traditional buildings were designed to be easily maintained and repaired. If your building contractor is proposing using materials or components that weren’t originally used, they likely haven’t understood the problem. This applies especially to any use of portland cement, damp-proofing systems, silicone waterproofing, or ‘tanking’ procedures.

flush pointing and limewashed used in a traditionally built building

↣ An example of rubble walling from a property built around 1900. Mortars were brought flush to create a flat face. Remnants of limewash indicate that the building was painted, which would have given an impressive, uniform appearance, despite being constructed of cheap rubble.

Recent History

Most traditional buildings have exposed stonework; this is a modern phenomenon. A visiting 18th Century person would look at our buildings – which they might have seen being built or in their prime – and call them derelict or unmaintained. From a conservation perspective they are in a state of managed (or often unmanaged) decay. A good proportion won’t see out the 21st Century.

This situation is amplified in rural areas because of the popularity of converted farm buildings. Most farm buildings date from the 18th & 19th Centuries and represented a significant investment on the part of their owners. They were typically well constructed and designed to be cheaply maintained with regular limewashing and simple repairs. Mixed fortunes and changing farming practices during the late Victorian and Edwardian periods led to the decline and loss of some of these buildings.

Those that did survive bore witness to two world wars and the economic depression of the 1930s. By the 1960s and 70s, when the conversion of these buildings took off, few had seen any meaningful maintenance in more than half a century. The ‘weathered’ exposed stonework that we maintain to this day is a product of that recent history. For softer sandstones and limestones, such tastes are, regrettably, to the detriment of future generations who might wish to enjoy these buildings.

Tip: Few buildings were designed to withstand the elements on exposed stonework. Flush pointing with non-hydraulic lime mortar (or, preferably, pointing and limewashing) is often the single most beneficial conservation measure a home-owner can make. Past and future generations would owe you a debt of gratitude!

Orientation / Aspect

Traditional, vernacular buildings were often built in slightly different styles on their exposed South and West elevations compared with the more sheltered North and East aspects. In rubble buildings, the S & W elevations often used the best, squarest (or indeed hand-dressed) stone to form tight joints between the stones. N & E elevations typically used more rounded, random stonework with more exposed mortar. The reason for this is simply because lime mortars (once set) are highly resistant to frost, but are more prone to driving rain.

The tighter stonework on exposed elevations presented less mortar to the elements. The front of most buildings are also normally South-facing, and so aesthetic concessions were also more considered – especially in later buildings.

Tip: It is worth considering these differences when repointing. The different construction methods won’t enable the same appearance to be achieved across the whole building. It would certainly be worth also considering limewashing the poorer quality stonework.

Pointing & Erosion

Red sandstones of the Eden Valley (and some limestones in Yorkshire) are very prone to crumbling and erosion. As mentioned above, this is an effect of modern maintenance habits, and decay (unless rectified) only accelerates. A building with signs of advanced erosion is likely to suffer significant problems with decades, and the range of mitigation measures becomes more limited as the situation worsens.

hot-mixed lime wall construction methods

↣ Illustration of the effect of erosion on the appearance of pointing mortars. To achieve a flush finish (which best protects the stone) eroded stonework require more visible mortar (right), compared with its original state (left). To preserve the original appearance, pointing mortars would need to be recessed, allowing erosion to continue.

Cement pointing will cause and accelerate erosion and should be removed (see more about lime and cement mortars). However, stone will also decay even if the wall has lime mortars, if those mortars have erode back into the joint (or is deliberately repointed recessed). Once stone has eroded the appearance of the wall is irreparably changed as the joints at the front of the stone widen.

Tip: Sheltercoats (limewash coloured to match the stone colour) can be used as a sacrificial coating for localised erosion – e.g. window surrounds or dressed stonework. Wider erosion indicates that the wall is not being managed in the correct way. Commercial ‘stone consolidants’ are irreversible and should be used with great caution.

Limewashing

Limewash has a softer appearance than even the most expensive paints and can be made in a similar range of colours. Indeed, despite the austere appearance of many old buildings today, they would have once been awash with colour!

The prep work for limewashing exposed stone is similar to conventional painting (typically steam cleaning to remove organic materials and careful removal of loose material). Made with quicklime, rather than lime putty, the limewash can usually be applied in 2 or 3 coats. A top-up maintenance coat might be necessary every five to ten years, although, unlike masonry paint, limewash won’t curl and flake. A limewash left untended will develop a weathered patina, whilst still performing some of its protective function.

Tip: If limewashing a whole building seems too drastic, consider doing a ‘feature’ elevation, or leaving the quoins and window jambs exposed. (Planning permission may be required in some areas, although it shouldn’t be refused).

Structural Cracking

Structural cracks usually appear for one of three reasons: because of loss of support from rotting roof or floor joists (unlikely in occupied buildings but commonly found during renovation projects); because of new openings built of cemented stonework; or because of very significant erosion of the original bedding mortars.

hot-mixed lime wall construction methods

↣ Rebedding a stone wall with lime mortars. Despite its nominal low strength, lime mortar pressed 4″ or 5″ into the wall will provide considerably more support than an inch of hard cement placed at the front.

The second of these is very common and occurs because the cemented stonework acts as a rigid block within a wall designed to move and flex with the seasonal wetting and drying of the ground. The builders or architects have, in this instance, singularly failed to understand the basic principles of solid wall construction. The latter (eroded bedding mortars) is less common on its own, but frequently acts to weaken a wall which can exacerbate the effects of ill-judged modern interventions. Cement pointing (if applied at depth) or inserted into cracks, can also initiate unwanted movement.

In serious cases, a structural engineer may need to advise on safety concerns, but more commonly simply rebedding the stonework in a soft lime or earth mortar will suffice.