Watch a video clip about the difference between traditional plasters and modern plasters.

Advice & Guidance

Walls

This section contains information about render finishes, plants, ground levels and air bricks.  There are separate pages dealing with masonry and timber.

Traditional render and limewashRender: Traditional renders are generally based on a mix of lime and sand. This makes them softer and more porous than modern cement renders, which can be extremely dense and impermeable. When rain falls on a lime-based render, it is absorbed then dries out naturally when the conditions are favourable. Lime renders are also flexible and will accommodate movement in the structure without undue harm.

Over time, lime renders will weather away, particularly where they are used in exposed locations, so it is advisable to note the condition of the render.

Your architect or surveyor may suggest some patch repairs to repair small areas of damage. Lime render can also be given a protective coating of limewash to help ensure its longevity but avoid using proprietary masonry paints or waterproofing substances on lime renders as these will disrupt the building's ability to ‘breathe'.

Patched cement render In contrast, cement renders are designed to be impervious and will crack if there is any movement in the structure. Such cracks will allow rain to penetrate the wall where it can become trapped and may promote decay. Cracks and areas of missing render should therefore be reported to your architect or surveyor. These can often be successfully patched or consolidated.

Alternatively, it might be worth considering whether the cement render could be replaced with a lime render.

 

This would improve the building's ability to ‘breathe' but care must be taken, as removing the cement render can cause damage to the fabric underneath. The potential harm to the fabric must be carefully weighed against the benefits of removing the render.

Bricks damaged by removal of cement render


Extensive plant growthPlants: Plants may enhance the appearance of buildings, but consider seeking advice about the control or removal of trees or climbers if there is evidence that they are damaging walls or blocking gutters.

Recent research has shown than ivy can sometimes provide a level of protection to old walls but in other cases it can be quite destructive.  If the walls are already in a poor condition then ivy can force joints open and damage the core of a solid masonry wall.

Planted borders around the base of the walls are a popular way to enhance the appearance of a building but do be aware that this may prevent the masonry drying out properly. The presence of large shrubs may also reduce access for maintenance purposes and air grilles or ventilation bricks may become blocked.

 

Action point: Clear away plant growth from around the base of the building and in particular from the ground gutter or drainage channel. The roots of plants and grasses can damage the integrity of the channel and impair its ability to carry water swiftly away from the building.

It is best to remove weeds by hand rather than using weed killers as the chemicals in the weed killers can penetrate into masonry leading to problems of efflorescence.

If you are unsure how to deal with ivy on your building seek further advice from your architect or building surveyor.

High ground levelsGround levels: High ground levels can encourage dampness so care should be taken to prevent earth building up against the base of walls. Ideally, external ground levels should be at least fifteen centimetres (six inches) below the internal floor level.

However, it may not always be desirable to attempt to reduce the ground levels around older buildings as this can have a negative impact on burials and archaeological deposits. If this course of action is deemed necessary archaeological advice should be obtained before any ground is disturbed.

 

Air bricks and ventilators: Air bricks and ventilators are used to circulate air through the voids under timber floors or pew platforms. If they become blocked, there will be less air movement under the floor, which may eventually encourage rot in the floor joists and floorboards. If air bricks or ventilators are broken, replacements can be obtained.

Decorative ventilatorMany older examples are decorative as well as functional and should be retained if possible. It is often a good idea to fit some fine mesh behind the ventilator to exclude rodents and insects.

Action point: Make sure that any air bricks or ventilators in the base of the wall are free from obstruction and clean them if necessary. A thin stick is useful for this purpose.

Further information:

© SPAB 2012