Lime plastering using traditional lime plaster offers advantages over cement and gypsum based materials for the internal plastering of traditional properties:
- Their porosity allows the structure to “breathe”.
- They can accommodate general movement better.
- Their self-healing nature reduces cracking problems.
- They can reduce condensation problems.
As with all lime plastering, the best outcome requires patience and careful control of drying and suction – the reward being a good looking and long lasting finish.
We also supply a range of clay plasters for use in traditional properties and new build.
Before starting any work, always check if the building is listed. You may need to contact the local authority Conservation Officer to discuss the project before proceeding.
Example Lime Plaster Specification on to Solid Walls
Remove any existing failed plaster and paint. Check the structure for damage. Look out for very thick patches of plaster because these could be load bearing. It may be necessary to plaster on top rather than risk rebuilding an area.
Dampen the substrate with clean water to control when lime plastering before applying each coat. Allow water to soak into the lath before the plaster is applied – control of suction is important but so is surface tension.
- Dub out any deep holes in the wall with a Haired Lime Mortar, re-building defects using like for like materials such as cob blocks, cob bricks or stone.
- Treat and counter batten wooden lintels before lime plastering.
- Apply a 3 mm harled coat of Secil Consolidation Mortar to provide a key to the masonry. Leave for 24-48 hours until ‘green hard’.
- Use Haired Lime Mortar to apply a 12-15 mm scratch coat. This will smooth the contours of the wall. Leave for 5-7 days until ‘green hard’.
- Use Unhaired Lime Mortar to apply an 8-10 mm float coat. Leave for 5-7 days until ‘green hard’.
- Apply a top coat of our Heritage Lime Plaster based on a very fine sand and lime putty in two passes totalling 3 mm. For the very smoothest of textures, substitute the second pass for a 1 mm skim of Regency Lime Plaster.
If the wall has a high residual level of moisture that cannot be eradicated (e.g. a high external ground level) it may be necessary to apply a waterproof barrier before lime plastering. We supply a waterproofing slurry for this purpose. Gauge backing coats of lime mortar with Argical M1000 to bring about a hydraulic set.
Limes are caustic. Always wear eye protection and protective gloves and clothing and follow the safety instructions on the labels.
Lime Plastering: Coverage
- 3 mm scat coat of Secil Consolidation Mortar, 5 kg/m²
- 15 mm scratch coat Haired Lime Mortar, 30 kg/m²
- 10 mm float coat Unhaired Lime Mortar, 20 kg/m²
- 3 mm top coat of Heritage Lime Plaster, 6 kg/m²