Due to the fact they are both applied by trowel, the general public and even some property professionals tend to confuse plasterwork and render. It is understandable to an extent, despite the fact they are very different materials, and if they have been damaged will require equally different techniques to repair them.
The most obvious distinction between the two is that plaster – either lime or gypsum based – is intended to be used inside buildings; although render does sometimes get applied as an interior as well as exterior finish. Traditionally, a sand/cement mix is often applied as a ‘scratch coat’ to provide the level base beneath the plaster top coat.
In certain circumstances, such as within period cottages, you will also see render used as the wall finish on its own, where the occupants or their architect decided the coarser surface suited the overall décor. Unpainted, however, render will always feel rough to the touch and tend to shed particles of sand or grit.
It also has to be noted that although pre-batched, so-called proprietary render systems – mainly silica or acrylic based – have been available from mainly European manufacturers for decades, it is only in recent years that their use has started to surge.
This is due in part to the revival of Modernism – probably encouraged by property programmes like Grand Designs – and some more basic economic factors.
Firstly there has been a quite serious brick shortage since the recession eased, encouraging developers, struggling to obtain deliveries, to switch to render treatments.
Then also there has been the big surge in energy prices and related increase in ‘fuel poverty’ that has seen Government force the big generating companies, such as npower and Centrica, to fund huge renovation programmes including CESP and now ECO (Energy Companies Obligation). A principal improvement made to many old solid wall type properties is the application of an Exterior Wall Insulation (EWI) system, which are nearly always covered by a proprietary render.
With an estimated five million solid wall homes to be thermally improved it seems likely that insulated render is going to overclad a large proportion, despite some conservationists’ concerns about the disappearance of ‘bricks and mortar’ from our urban streetscapes.
One of the problems with render, however, and a main reason why social housing landlords have generally preferred not to specify it as a wall finish, is that it tends to be high maintenance. Rendered elevations can be expected to dis-colour with age and weathering while they are also susceptible to knocks and damage. A touch from a car bumper or youngsters repeatedly kicking a football against the wall will normally leave their mark. There are also issues with poor adhesion of systems or structural movement in the building.
None of these scenarios are simple to put right. Successfully patching them is beyond the skills of your average handyman and even someone experienced in applying render can struggle to match the surrounding area with fresh material. Their advice and that of building contractors in general is to hack it all off and start again – an answer which can cost many thousands of pounds.
This is why Plastic Surgeon has invested a lot of time and effort in developing its specialist render repair service, in order to resolve most problems affecting rendered surfaces.
When called in by a client to look at problems with areas of render, Plastic Surgeon’s regional operations manager or technical sales staff will consider the overall ‘health’ of the surface. For example, if there is evidence of cracking you need to consider whether there may be a problem with subsidence, or possibly of wall ties corroding and effectively forcing the bed joints apart. Such situations require a structural remedy before attending to cosmetic considerations.
There is also the possibility that the render coat is delaminating due to poor initial bond strength or subsequent thermal movement. In this case the render will sound hollow if tapped and must be replaced.
Crucially, Plastic Surgeon can offer an accurate quotation on remedying different types of damage including small cracks, scrapes, gouges, holes and missing patches: any of which normally present a significant cost saving compared to having a building contractor hack off and re-render the entire elevation. The latter scenario can also affect adjoining areas as metal mesh beads are normally embedded in the render to form the corners, and are prone to disturbance.
Where damage is limited, the company’s repair technicians will normally create a hole up to 100 mm in diameter, reaching down to the substrate to create a confined work area.The surrounding wall is masked off and the hole filled using Plastic Surgeon’s System 140: a cementitious based monocouche render that is through-coloured and can be applied in a single coat up to 25 mm thick. Any depth greater than this and the Finisher will initially utilize products from the company’s stone repair system to build it out.
All of Plastic Surgeon’s repair technicians are trained in colour matching and System 140 offers a choice of 10 basic dry powders for them to mix from to match original shades. More vibrant and unusual colours can be ordered from the manufacturer; while if there are multiple areas to patch it may be most effective to repaint the entire wall afterwards.
Also of importance to concealing the render repair is getting the surface texture or reflectance right; which can be achieved in a variety of ways. Where a very smooth surface is required this will probably be done using the blades which the Finishers employ to apply the System 140, while different degrees or roughness can be achieved by rubbing with a sponge or possibly a wooden float. The Finishers can also replicate other effects using the tools they carry as part of their van kit.
Depending on the extent of the repair and the ambient conditions at the time the work is being carried out, it may be necessary to use a heat gun to part dry the render repair, but this has to be judged very carefully to avoid shrinking the new material. It should also be noted that until the monocouche is thoroughly dried, it may appear darker than the surrounding original render.
Over recent times Plastic Surgeon has intervened successfully on behalf of clients facing quite daunting problems with render damage. This has encompassed contracts on old listed buildings – including those featuring specialist ‘stucco’ render with fake masonry joints – through to contemporary construction projects where site vehicles or scaffolding have damaged insulated render systems. The Finishers have even been able to restore elements such as entablatures carrying emblems and even a sign on art deco building where the lettering was made of sand and cement.
As with other classes of cosmetic repair, using Plastic Surgeon’s render repair service is almost always the economic alternative to replacing damaged surfaces.
Tell us about your damage and we can provide a no-obligation quote.