Earth & Lime Mortared Wall Consolidation

This page summarises an ongoing project to stabilize the remains of a derelict traditional field barn in Cumbria. As well as preserving the structure for future generations, it also allows us to test the performance of traditional building materials in a very exposed setting. For the latest information on historic mortars used in vernacular buildings I would recommend visiting Hotmixedmortars.com.

A .pdf report on this project, including further information about the mortar types used can be downloaded here.

reconstruction of a traditional barn wall near Appleby, Cumbria.

↣ Remains of a probable 18th century or earlier field barn in Cumbria. The recently collapsed wall clearly showing the earth-mortared core, whilst the remaining wall tops are exposed to the elements.

History

The barn stands in an area of large enclosed fields, going by the name Benbank, within the parish of Murton & Hilton. The area is adjacent to what, in Medieval times would have been one of Murton’s communal open fields, and was probably an area of grazing and hey meadows. It continues in this function today.

The remains of the existing barn were once part of a larger long, narrow building (measuring 50′ x 20′), alongside a smaller building, of which nothing remains. The buildings were mapped in 1858, and the south-east gable was built into a boundary which existed in 1757. Remains of the original building can be seen in the existing boundary
wall.

By 1897, the two original buildings were mapped as being derelict, and by 1911 were modified into the existing, smaller structure seen today. During the mid 20th C. the structure was modified again to take a single pitched tin roof, after presumably falling into disrepair. That roof blew off some 20 years ago, and the remaining walls have rapidly deteriorated since.

Construction

The two surviving original walls were built of stones cleared from nearby fields, and constructed with an earth mortar made of local subsoil and possibly a small amount of lime, for added strength. The construction and size is similar to many surviving early buildings locally, which were built using cruck timbers and a steeply pitched thatched roof. Most such buildings were modified in the 18th & 19th centuries to incorporate a modern truss roof, which maximised the amount of storage space during the booming period of agricultural
advancement.

traditional field barn rebuilt in earth mortar and ready for lime pointing: near Appleby, Cumbria

↣ Recently collapsed areas of wall rebuilt with earth mortar, made with material recycled from the existing wall with supplementary material dug locally. The mortar is used relatively wet, but firms up quickly and provides a remarkably solid structure.

The exterior has no original pointing, but was heavily repaired with cement when the tin roof was added. The interior contains two surviving lime mortars: one made predominantly of very fine grained sands and silts mixed with high proportion of lime, much of which remains in aggregate form; and a second made of courser, better graded sands and a more thoroughly mixed lime binder. The latter probably dates from when the building was reconstructed around 1900, whilst the former likely dates back significantly earlier.

Conservation Threats

Buildings in such a ruinous state are unlikely to every be restored to their original state, but their presence as ruins contribute to the character of the landscape and its history. The greatest threat to such structures is their rapid disintegration – there would very likely be little standing of this structure within a matter of decades – and the removal of stone, which is valuable for modern stone-faced construction and as general field wall repairs. The structure has few, if any, statutory protections.

Stabilization Proposals

Owing to the rapid decay of the building, it was decided to reconstruct and stabilize the corner of the original surviving walls, which has seen recent large-scale collapses. This would provide structural support for the surrounding stonework, and allow a capping to be installed. Capping of exposed earth-built walls is essential to limit the ingress of water, which is the primary agent of decay.

lime pointing of traditional stone building, Cumbria

↣ Lime pointing of the interior wall. Several mixes were tested, with an earth-sand-lime mix showing greatest potential and being particularly effective at preventing the mortar drying to quickly (which was a problem in very strong winds).

It was proposed that the wall would be rebuilt with earth mortar – in keeping with the original structure – and pointed in hot-mixed lime inside and out, with the inside also receiving a hot-mixed limewash, as was typical of most agricultural buildings. The capping would be turf, which it is hoped would bond well with the irregular surface and be sympathetic to the appearance of the ruin. It would also provide an opportunity to test the use of such capping materials, with risk of irreversible effects.

Practical Considerations

Owing to wet conditions during the Summer 2019, it was not possible to get vehicular access to the site. Consequently, any additional materials and equipment had to be brought in by hand. In reality the only additional materials were sand and quicklime, which in its dry state is relatively light. Water was sourced from a nearby syke, and mixing of mortars done by hand. The biggest challenge was sourcing additional subsoil for the earth mortar. In these respects the work must have been remarkably similar to those faced by historical builders, and, ultimately, are a good indication of the inherent simplicity of the materials and techniques used.