Traditional

Traditional Plasters

Sympathetic with older walls

After World War II, using Portland Cement in render and pointing, became the economical solution. However Portland Cement can trap moisture behind it when applied. It can also break down the Lime cycle by not allowing Carbon Dioxide to reach the lime cement. This can cause pointing, render and plaster to fail. Natural Hydraulic Lime (not to be confused with Hydrated Lime) comes in three strengths for interior and exterior walls. NHL 2 being the weakest set, NHL3.5 and NHL5 being the strongest set. Hydrated Lime is often added to Portland Cement to increase workability and make the cement more pliable. If you’re home was built before World War II it likely was originally built using NHL 3.5 and therefore care and consideration should be taken to choose the right material in the long term. You can test your walls for lime, by splashing a teaspoon of white vinegar onto your test area. If you can hear fizzing then the lime is reacting with the vinegar.

Other materials to look out for

Modern Gypsums, such as Thistle Multi Finish and Thistle One Coats. Are also going to stop Carbon Dioxide passing through and will also trap moisture behind. This can lead to cracks, walls failing over time, and damp issues which can lead to black mould. Modern paints with silicone plastics can still damage the paint work later if moisture becomes trapped. Even if the manufacturer claim the paint is breathable damage can still be caused if enough water is not released which results in the paint being force off the surface by moisture release.  Heritage plasterers recommend limewashes and silicate mineral paints or linseed paints to have maximum breathability and allow moisture to escape.  This book contains plenty of information to help you make the right decisions in your period property.

The solution

The solution is obviously to remove modern plaster that is causing the failure of moisture to move freely, and to do this would be to use NHL to plaster indoors or alternatively render outside. A 25kg bag of NHL 3 costs around £25 and washed plastering sand costs very little. The cost of a Lime Finish is more expensive and has to be transported from the mainland is pre slaked tubs. A 10kg tub including postage costs around £20. Although in the long term its cheaper to replace the lime mortar every hundred years than to replace the bricks every ten years.
© This site was packaged and coded by Xara, designed using Xara Web Designer by Alexander Wilson.
Exterior Lime preservation work at Osborne House.

Lath ceilings and cracks

Old lime and plaster ceilings attached to lath are notorious for deep cracks. This is fairly common if the original plaster is nearly a century old. It’s actually a testament to traditional plaster if the ceiling can last a century with only a few cracks, however its usually the plaster loosing its grip to the laths that causes cracks. Repair: These cracks can be channeled out and repaired with plaster of paris for a temporary solution. Renovation: Check the strength of the joists. Reboard over the lath and plaster; or remove the lath and plaster and board onto the joists using plasterboard. Restoration: Relath the ceiling and use traditional methods to plaster the ceiling the original method.

Tiling over lime plaster

Ideally you want to avoid tiling over lime plaster walls if the walls are frail (perhaps you may want to replaster  the wall first before tiling over as its impossible to replaster a traditional wall with tiles on). If the wall is in good condition you should ask your tiler to use a Pure Lime Grout. Such as found here and even use a lime based tile adhesive. It should be noted also that if you remove coving and skirting then you’d be good to screw HardieBacker® Board to your joists and tile over the HardieBacker® Board without the need to replaster or remove old plaster.
Lime Finish on Chimney Breast
Application of Lime Plaster
Sand and Lime Mix in Bucket
lime frieze restoration
Decorator & Plasterer

Traditional

Plasters

Sympathetic with

older walls

After World War II, using Portland Cement in render and pointing, became the economical solution. However Portland Cement can trap moisture behind it when applied. It can also break down the Lime cycle by not allowing Carbon Dioxide to reach the lime cement. This can cause pointing, render and plaster to fail. Natural Hydraulic Lime (not to be confused with Hydrated Lime) comes in three strengths for interior and exterior walls. NHL 2 being the weakest set, NHL3.5 and NHL5 being the strongest set. Hydrated Lime is often added to Portland Cement to increase workability and make the cement more pliable. If you’re home was built before World War II it likely was originally built using NHL 3.5 and therefore care and consideration should be taken to choose the right material in the long term. You can test your walls for lime, by splashing a teaspoon of white vinegar onto your test area. If you can hear fizzing then the lime is reacting with the vinegar.

Other materials to

look out for

Modern Gypsums, such as Thistle Multi Finish and Thistle One Coats. Are also going to stop Carbon Dioxide passing through and will also trap moisture behind. This can lead to cracks, walls failing over time, and damp issues which can lead to black mould. Modern paints with silicone plastics can still damage the paint work later if moisture becomes trapped. Even if the manufacturer claim the paint is breathable damage can still be caused if enough water is not released which results in the paint being force off the surface by moisture release.  Heritage plasterers recommend limewashes and silicate mineral paints or linseed paints to have maximum breathability and allow moisture to escape.  This book contains plenty of information to help you make the right decisions in your period property.

The solution

The solution is obviously to remove modern plaster that is causing the failure of moisture to move freely, and to do this would be to use NHL to plaster indoors or alternatively render outside. A 25kg bag of NHL 3 costs around £25 and washed plastering sand costs very little. The cost of a Lime Finish is more expensive and has to be transported from the mainland is pre slaked tubs. A 10kg tub including postage costs around £20. Although in the long term its cheaper to replace the lime mortar every hundred years than to replace the bricks every ten years.
© This site was packaged and coded by Xara, designed using Xara Web Designer by Alexander Wilson.