Earth Mortars

Technical challenges come in all shapes and sizes. They are not restricted to castles and grand palaces, they can appear in modest cottages. A small renovation project grew arms and legs this week, when the removal of some cement harling from the stonework of their small cottage revealed a catalogue of horrors.

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Removing cement harling from chimney MAAC Studio conservation architect

Removing Cement harling reveals masonry issues

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The building was owned by a building contractor who carried out a “renovation” in the 1980s. The wrong techniques and materials were used, but all of the problems were hidden by cement harling outside, plasterboard inside and a fresh lick of paint.

This cottage was built using early masonry techniques, before the Victorians started to demand certain standards. The wall core is therefore a clay earth mix with a bit of lime thrown in, a cost-effective solution for the period, that is fine but need to understand it, look after it and keep on top of maintenance. It is vulnerable and if there is any water ingress, the mortar in the wall core will begin to disintegrate and turn to powder.

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Voids in masonry reveal extensive damage to wall core MAAC Studio conservation architect

Open joints reveal voids in the wall core where earth mortar has disintegrated

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Fast forward to 2019.

Water has been getting in for years, the wall core has been washed out and we are left with a gable chimney that is little more than a stack of loosely fitting stones. The stability of this structure has been compromised.

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Interior of stonework shows extensive damage MAAC Studio conservation architect

Voids in the wall core extend right through to interior

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There is a solution and our client was relieved to learn that they don’t need to rebuild the gable from scratch. It is going to involve specialist ties and grout injection using a specialist lime mortar mix. When were finished it is going to be as good as new.

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MAAC studio are accredited conservation architects and principal designers working with traditional buildings throughout Scotland. 

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