Lime Pointing a Yorkshire Barn Conversion

“Private residence, Arkengarthdale, Yorkshire Dales”

This page details a current project to repoint a 1980s field barn conversion in the Yorkshire Dales. The building had been extensively renovated, including raising the roof level and inserting numerous new windows. The building sits in an exposed location at an altitude of over 400mASL (about 1,300 feet). Cumbria Stone Walling was asked to reinstate a more traditional lime mortar pointing.

replacing modern cement pointing with lime mortar in the Yorkshire Dales

↣ Repointing a barn conversion with lime mortar in Arkengarthdale, Yorkshire Dales.

What is pointing?

Pointing is often seen as a superficial cosmetic finish or as something to ‘keep out the weather’. In traditional buildings the situation is more nuanced than this. Given that the original owners of such buildings staked everything on their sound construction, with no social safety net if life handed them a curve-ball, some of these nuances are still worth heeding even today.

1) Pointing mortars (usually lime-rich) protect the softer building mortars which, until well into the 1800s, were normally an earth mortar of clay, sand and lime. These softer mortars are critical to the stability of the structure and their loss is a non-trivial matter.

2) Stonework was rarely exposed, except in grand buildings. That is to say, pointing is not really an authentic practice – but instead stems from an idea of recreating the weathered, unmaintained appearance of old buildings.

Of course, some non-residential buildings were built with bare stone and exposed mortar (pointing, as we would say), where the local stone allowed for very tight joints. In these instances, the stone acted to deflect inclement weather and the small area of exposed mortar would have been relatively unstressed and quite durable. In all other circumstances, ‘pointing’ mortars were extended across most of the stone to create an even finish – which would have been either rendered and limewashed or just limewashed.

The limewashed finish was easy to maintain and would have protected the fabric of the building from more expensive repairs.

Structural Maintenance

The take-away message from this should be that ‘if there are historic mortars in a building they are there for sound economic reasons – and the smart money is on replacing them where lost or eroded’. The conversion of this building followed some alternative logic.

cement pointing applied to barn in Arkengarthdale in the Yorkshire Dales

↣ Cement point was applied in the belief that it would be more ‘hard-wearing’. In reality, cracks occur as the building moves naturally, allowing water to saturate the wall and cause important structural mortars to erode further.

Cement has high compressive strength but low flexibility. In old buildings, most stonework has stone-on-stone contact, so the compressive loads on building mortars is relatively low. They do, however, move significantly – owing to the absence of modern foundations – and so mortars require high flexural durability. Earth and lime mortars possess these qualities. Builders used such materials because they worked.

During the conversion of this traditional barn large areas of original mortar were removed or already lost and not replaced. Additionally, during the inserting of new window openings large amounts of stone which fills the middle of the walls were also lost. The consequence of this was that large areas of stone were loose and unsupported, save for the cement pointing at the face.

replacing cement pointing with earth bedding mortars and lime pointing

↣ The cement pointing was removed, and any loose stones rebedded in an earth mortar, before re-pointing in a hot-mixed lime mortar.

Lime Pointing

For most of the building I used a simple clay-sand-lime mix to rebed any areas of stonework, except in vulnerable locations where lime mortar was used. The pointing was done with a hot-mixed quicklime mortar, with a small addition of terracotta dust.

The rudimentries of the mix were: 1.5 parts quicklime, 1 part limestone dust, 1 part soft yellow sand, 1.5 parts grit sand, plus some coarsely crushed tile and limestone chippings. After slaking, this would give a mortar slightly richer than 1:2 binder to aggregate.

The following external links provide information on the historic uses of hot-mixed lime mortars, and Historic England’s current research into their use in conservation repair.

lime pointing of exposed stone building in yorkshire dales

↣ Lime pointing brought almost flush, whilst still retained exposed stonework. Originally, very little stone would have been visible. The building would have been strikingly new. when new.

Setting a level to repoint to on irregular stonework is a tricky issue. Originally, mortar would have covered virtually the entire stonework. Reinstating this would have several practical advantages, but would significantly alter the appearance of the building in the short-term. This is likely to be an area where planning authorities will having to step up.

Recessing the pointing to reveal more of the stonework is prone to leave irregular, often small, areas of pointing which can be less durable. The visual appearance of recessed pointing also changes with differing lighting angles. Given the exposed location, I opted for a relatively full pointing, assume that a modest amount of erosion would occur over the first few years. Once stabilized, mortars will find a degree of ‘equilibrium’ with the prevailing weather that is difficult to artificially replicate. Patience in this regard, brings its own rewards.

exposed stonework and lime pointing on a Yorkshire barn

↣ Oblique lighting shows the slightly recessed pointing, which is what allows that pattern of the stonework to be picked out (as seen in the picture at the top of the page).

More details on the structural issues and lime mortars used on this project can be found here (link pending).