Mineral / Lime Thin Coat Render

Lime render, in thin coats

Lime thin coat renders are a modern form of natural hydraulic lime, a material that has been going onto buildings for hundreds of years. Lime is the most breathable render available: it lets moisture leave the wall instead of trapping it, and it expands and contracts with the building rather than resisting it. That is what makes it right for older properties, and for timber-framed ones.

Why breathability matters on an old wall

A solid older wall deals with water by letting it evaporate off the face. Put an impermeable modern render over it and the moisture has nowhere to go — it sits in the structure until it pushes the render back off, taking the surface with it. Lime leaves the wall able to work the way it was built to work.

What it is made of

Modern lime renders combine hydrated lime with pozzolanic additives, sand and mineral fibre fillers, so they go on much like a conventional sand and cement render while keeping the properties of traditional lime. As it cures, lime takes carbon dioxide back out of the air and sets towards a limestone state, which is where the durability comes from. A glassfibre reinforcing mesh runs through the system and gives it enough flexibility to absorb thermal movement without crazing or cracking, generally without needing expansion joints.

It can go over what is there

Where the existing render is sound, the lime system can be applied straight over it — no hacking off, and no priming. At Brither Cliff House on Onchan Head it went over the old face brickwork and was finished in KEIM mineral paint, on a seafront elevation, which is about as hard a test as this Island sets.

Where it is used

Historic and listed buildings, conservation and restoration work, and new build alike. The projects below run from cottages at Bride and Bradda Head to Braddan Cemetery Chapel and a terrace at Peel.