Gamekeeprs Cottage Seaham

A period 18th century property covered in a modern O.P.C render. The damp issues were quite severe.

• Moisture trapped in walls
• Original lime mortar had started to break down due to continued moisture, returning to earth lime
• Moisture in inside property – dehumidifiers could not cope with
• Major remedial works required

Work Carried out:

• Remove all render, repair and replace all lime mortar
• Replace damaged sandstone
• Form new “punched faced” quoins on site

Result – a structurally strong, dry and happy property

Dean Bank & Ferryhill Literary Institute

This is a 1908 lime built structure. In essence old buildings exposed to elements are continually absorbing moisture and the ability for the moisture to evaporate again is crucial to the well being of the structure. In ignorance the property had been repointed with modern Portland cement. Using cement based mortars locks in moisture which results in dampness which leads to general building fabric decay. Problems arise when the building has been “repaired” with inappropriate materials through lack of knowledge.

Issues

• High moisture content in masonry
• Wall tie failure
• Horizontal and vertical movement
• High number of spalled brickwork due to moisture
• Severe vertical fractures to masonry

Work Carried Out:

• Remedial Strategy
• Remove all modern mortar
• Replace all spalled and split/cracked brickwork
• Locate and replace all wall ties
• Install “bow ties” through masonry into joists along with sets of helibeams to provide lateral and horizontal restraint
• Install chords and beams the full length of the elevation
• Repair cills
• Repoint using lime mortar

Benefits of lime mortar 

Lime mortar has been used in construction for thousands of years and is still valued today, especially in conservation, restoration, and sustainable building. Compared to modern Portland cement mortars, lime mortar offers several important benefits:

1. Flexibility and Breathability

Accommodates movement: Lime mortar is softer and more flexible than cement, so it can tolerate small shifts in a building without cracking.

Moisture regulation: It is porous and vapour-permeable, allowing walls to “breathe.” This helps prevent moisture from getting trapped inside walls, reducing problems like damp, mold, or frost damage.

2. Compatibility with Historic Buildings

Traditional stone, brick, and timber structures were originally built with lime mortar. Using lime for repairs ensures compatibility in strength, appearance, and performance.

Cement mortars can be too rigid and strong, leading to damage in softer historic materials, while lime mortar works in harmony with them.

3. Durability and Self-Healing

Autogenous healing: Lime mortar has the ability to “heal” small cracks. When rainwater dissolves free lime, it can redeposit as calcium carbonate in cracks.

Resistant to weathering: Properly applied lime mortar can last for centuries, as evidenced by many ancient buildings still standing today.

4. Sustainability and Environmental Benefits

Lower embodied energy: Lime production generally uses less energy than cement manufacture.

Carbon reabsorption: Lime mortar reabsorbs carbon dioxide from the air as it cures (carbonation), partially offsetting the CO₂ released during lime burning.

Recyclable: Lime mortar allows for easier deconstruction and reuse of materials since it can be more gently separated from stone or brick.

5. Workability and Aesthetics

Easier to work with due to its smooth and plastic consistency.

Longer setting time than cement, which gives masons more flexibility during construction.

Can be finished in a range of textures and natural tones, blending well with historic and traditional buildings.

In summary:

Lime mortar is breathable, flexible, and sustainable, making it ideal for historic building conservation and environmentally conscious construction. It protects buildings by allowing movement and moisture control, while cement mortars can often cause long-term damage in older structures.

Finally for enthusiasts a quick chemistry lesson

1. Stone spalling when pointed with modern mortar
2. Acid rain equals sulphur dioxide this attacks the binder in stone which is calcium carbonate.  When calcite is attacked it forms calcium sulphate which is gypsom this is all due to trapped moisture in the masonry.