This Oxfordshire cottage has some interesting history, in fact it caught fire sometime around 1950. The left hand side of the front elevation and the top of the gable elevation were completely rebuilt. This is assumed to have been done with a cement-lime mix. The bedding mortar was extremely hard like cement however it reacted vigorously when exposed to an acidic solution. This is due to the high alkalinity of lime (Calcium carbonate). The rest of the building was bedded with a traditional earth-lime mortar. This is a beautifully soft, brown material that breaks to a fine powder between the fingers.
The building was later completely repointed with an extremely rich cement mix. The issue here is that the cement mortar is inflexible and will crack due to different expansion/ contraction rates to traditional materials. This can result in the ability for rainwater to seep into cracks and cause dampness. Once the moisture has worked its way in through the cracks it will find it extremely difficult to get back out as cement does not have the ability to allow for the capillary movement of moisture back to the surface to evaporate. Solid walls are expected to soak up water during wet conditions and then dry out when the weather clears. The thickness of the walls prevents moisture from reaching the internal surface. A large crack existed near the rain water hopper which may explain the dampness the that section of the wall - visible in the image above. This is expected to dry out over time but may take many months. Haired quicklime mortar (slaked with our own blend of sands on site and applied hot) was used as it's the best performing and most appropriate lime for external pointing.
This was quite an extensive project spanning 5 months and 3 seasons! The use of hot-mixed mortars made it possible to progress work through freezing temperatures. Hot-mixed mortars can be used successfully through winter providing the daytime temperatures rise above freezing and the mortar is adequately protected overnight.
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