THE RIGHT
SERVICE FOR YOU
PUTTING FABRIC FIRST

THE RIGHT
SERVICE FOR YOU
PUTTING FABRIC FIRST

THE RIGHT
SERVICE FOR YOU
PUTTING FABRIC FIRST

Render Systems

Rendering is a façade covering applied to either a new or refurbished property that is cost effective and protects the outside of the building from water penetration. One of the most commonly asked questions are “Which render product should I use on my Property”

exterior-terrace-render-edit

In the UK we have only just found the benefits from Rendering our properties compared with the rest of Europe, therefore the questions asked is which of the systems that are on the market are best to use, should it be a Lime Render, a Cement Render or a  Pebbledash and Roughcast Render.

The older the property the use of more traditional products such as pebbledash or roughcast render finish will be found. Pebbledash is formed when fragments of stone are literally thrown at the wet render called Dash Receiver and pressed in, whereas roughcast involves the pebbles or stone being mixed into the mortar before it is applied to the walls. The latter produces a softer finished texture which is usually painted.

Traditional cement-based render is applied in two coats. The first ‘scratch’ coat is around 10mm thick (or slightly thicker on old and uneven walls) and sometimes includes a waterproof additive. It is scratched while wet to form a good key for the second ‘floating’ coat.

applying-render-editThe floating coat is usually around 15mm thick and is smoothed flat with a straight edge, before being rubbed over with a plastic float.

Finally, the render is finished with a damp sponge to remove marks and little bumps and then painted.

The problem with these types of renders, other than the overall thickness being often over 30-35mm thick, is that cement-based renders are more likely to crack as they are less flexible than the substrate, which is important especially on South facing Walls. Cement renders as less vapour open, which means that water vapour will freeze in the render causing the render to blow and fall off.

Render generally performs really well, but cement-based renders tend to work best in situations where the underlying brickwork has been built using cement based mortars, which are fairly rigid. Where softer lime mortars have been used, the render has to be able to cope with more movement; lime-based renders are better at dealing with this.

In either situation, though, cracks as a result of structural movement can occur. Render can also be vulnerable to trapped water. For example, if pebbles have become loose in pebbledash, water can get in. If this water freezes, the render can crack or, worse, fall away in sheets. Other problems include salt crystallisation around cracks.

Cement based renders tend to have a shorter life than both the modern polymer mixed mineral versions as well as lime-based renders, as they are more liable to shrinkage and crack or break off more easily. Lime-based renders can still be seen on some buildings dating back centuries.

Should I Use a Lime Based Render?

If you are repairing a traditional building that uses lime-based mortar or some elements of it in the render, then you should certainly do so. Lime is less dense and more vapour permeable.

Owing to its breathable nature, lime render also tends to deal with movement better than cement-based products. It does tend to be more expensive but is widely considered the appropriate choice for many traditional, and traditional-styled new build homes.

What are the New type of Renders Like?

When looking at rendering your home, you will more than likely come across the term ‘monocouche’ render, or polymer mixed mineral renders. While both cement-based and some lime renders are mixed on site with sand, and applied in two or more coats, monocouche and polymer mixed mineral renders come supplied in bags ready for mixing with water and can be applied in the traditional way with a trowel, or sprayed on. Monocouche renders require only one coat, whereas the polymer mixed mineral renders as usually applied in 2 or more coats dependant on the finish required.

These renders are usually pre-coloured in pretty much any colour you choose and can around 15mm thick. They also typically have a range of finishes which can be acrylic based, Silicon, Silicate, Nano Silicon as opposed to lime or cement-based. They’re are more flexible and crack-resistant, when compared to traditional renders, and are water vapour permeable. Nano Silicon finishes claim to be self-cleaning, which work by the rain washing away dirt.

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  • We are now able to offer a complete building system using our with monolithic clay block & insulated raft system,