Application - Inappropriate Finishes/ Detail

Lime Mortar - Inappropriate finishes / detail

1. ‘Ribbon’ or raised pointing not only has an aggressive character but also provides a ledge that water can sit on and penetrate the fabric or the wall, during the winter the destructive effect of this can be exacerbated as the water can freeze and displace the pointing. Pointing should be flush with the face of the masonry/brick so that the wall can shed water as efficiently as possible.
2. Recessed pointing has the same effect as ‘ribbon’ pointing (above) as it can provide a ledge for water to sit on and to enter into the fabric of the building.
3. Thick mortar joints should be avoided and pinning/gallet stones are inserted to reduce the joint size and to combat shrinkage in the mortar.
4. The use of inappropriate coloured aggregates can cause pointing repairs to be visually unsympathetic to the building. As well as providing ten standard coloured mortars we also provide a mortar matching service and are happy to advise customers on their projects.
5. Pointing is finished by being struck by the trowel drawing fine particles and lime to the surface. This produces a very close texture and can be unappealing to the eye; it will also produce a very light-coloured finish relative to the advertised colour. Trowel struck pointing has inherent weaknesses as lime pointing needs to be beaten and compressed back into the joints as it is carbonating to reduce shrinkage and minimise cracking. 

Resolution

Use appropriately skilled craftsmen to undertake work, if you are undertaking the work yourself it is recommended that you at least undertake a training course.

‘Ribbon’ and recessed pointing should be removed and replaced with flush pointing. Thick mortar joints are likely to have cracks in them and will fail over time; they are likely to require raking out and re-pointing with the inclusion of pinning stones to combat shrinkage. 

Trowel struck pointing is likely to have cracks in it and may well fail over time. It should be removed and reapplied in accordance with manufacturer’s guidance.

As well as providing training courses and producing the instructional ‘The Lime Handbook’, Ty-Mawr does provide an on-site supervision and an advice service that can be requested.