Services rendered – a big cover up?

Render is a building material that’s popular on external walls. Used well it can really set off a property to its best advantage. Sometimes referred to as stucco, it’s often a sand and cement mix, but can also be pebble dash, rough cast, Tyrolean or lime. Acrylic premixed renders can also be used and these offer superior water resistance and strength. Like plaster in house interiors, render can iron out any unevenness in the wall surface or cover up the wall, if is made of something you wouldn’t want displayed – such as breezeblocks, or a doorway or window that has been built up. The trouble however is that external render can also be used to conceal a multitude of sins, such as cracking in the wall, deteriorated building materials or poor workmanship.

Protect and revive

Render is used in construction for many reasons. It can improve weather resistance, by reflecting heat from the sun and preventing water penetration by creating a protective cover. Or it can be used for purely aesthetic purposes. It’s widely seen on whitewashed properties in hot countries, in Greece and Spain for example, as a resilient and protective external covering. Sometimes however it is used as a ‘quick fix’ to cover up possible defects. Render can be easily applied to brick or blockwork, concrete or stone using trowels. It can be textured as it’s being applied – this is sometimes simply done with brushstrokes, to give the surface a textured finish when it is set. Once the render has dried out, it can be painted. Although it’s usually used on exterior walls, it can sometimes be used as a feature on an interior wall too.

Years ago, pebble dash was an easy way to improve the external appearance of a building. The render is applied and then small pebbles are literally thrown at or pressed into the still-wet surface, so they stick. Afterwards, the finished effect could be painted, but was often left ‘natural’, which was a grey cement with coloured stones inset. Many old buildings suffered as a result of this fashion and some attractive original brickwork and stonework was covered up. Only when properties came to be renovated was the building’s true beauty revealed once more.

What lies beneath?

When our surveyors are carrying out valuations and surveys – particularly on old properties – we are wary when we find render has been used externally. Crazed cracking is an easy-to-spot defect when evaluating properties. Render used to consist of a weak lime, sand and cement mix or just lime and sand. Both of these gave some flexibility, but lime wasn’t a very healthy building material to be around and was phased out. Modern renders tend to consist of just sand and cement, which runs the risk of shrinkage. This leads to the classic spider’s web of ‘crazed crack’ patterning on external walls.

Any cracks to render cause problems and should be addressed at the earliest opportunity – sometimes a filler will suffice. If the crazed cracking is on an elevation that is exposed to heavy weather conditions, such a driving rain and sun, on a regular basis, this will allow water to encroach behind the render, and become trapped between the render and the wall. Over time this process of constant drying and wetting brings the salts to the surface of the brickwork, which will loosen the render. Frosty conditions can cause a great deal of damage with expansion too. This can loosen render and eventually sections of the covering will simply fall off in patches. Cracking can also be the result of the render being applied too thick (render should be built up in layer, with a thinner key coat applied first), with too rapid a drying time, or where a chemical additive has been used.

Tell-tale signs

Any type of cracking in render is usually a sign of issues with a building’s strength and structural integrity – be it horizontal, vertical or diagonal cracking. Each type of crack will need to be assessed, before the problem can be diagnosed. Some of these cracks can be due to ground movement and settlement – if the foundations have been undermined, for example. Other factors can be to do with loading or alternations that have been made to the building – a new window inserted, for example, with an insufficient lintel – or an actual defect within the wall itself.

When you’re looking at a property, ask yourself – has the render been applied for purely aesthetic purposes, or is there an ulterior motive? If you suspect the render at your property – or at one you’re thinking of purchasing – may be concealing something that could cause problems, it’s worth chatting to our experts. They will be able to ascertain what could be causing it and advise you on your best course of action.