Ways of dealing with damp penetrating rendered walls
We live in a detached house that is rendered but is now showing signs of hairline cracking. Over the last few months we have also noticed that damp patches in some of the rooms, leading us to think that the render is failing. We have seen advertisements for protective coatings and some of our neighbours have had these applied to their houses. They come with a 20-year guarantee so we are very tempted, particularly as we have had a quotation and they appear to provide an extremely cost effective solution. Have you any knowledge of their effectiveness?
Unfortunately I have no firsthand knowledge of these systems. However, if the deal looks too good to be true then it probably is. Essentially there are no quick fixes with buildings. Furthermore, any guarantee is only as good as the company giving it. Many are run on a franchise basis so whether they will still be trading in 20 years is debatable. The guarantee therefore has limited value.
With regard to their effectiveness I have no doubt that under laboratory conditions they can prove their products are watertight. Applying the same coating to a variety of substrates such as brick or concrete that are then exposed to the elements is a very different matter and I am not convinced it will provide a good long-term investment.
The fact that your walls are damp does suggest the render is failing and moisture is being transmitted across a solid wall, most likely constructed from soft brick. The cementatious rendering is preventing the walls from breathing so that moisture is either being transmitted through to the inside or is accumulating under the render and therefore causing cracks to appear. Covering the render with a waterproofing system will ultimately only make the situation worse. Ideally, the old render needs hacking off and replacing with a lime render that can be decorated using a lime wash. This will allow the wall to breathe and function as originally intended.
We would like to extend our house but the development control officer has confirmed that we need a ground investigation report to accompany the planning application. This is despite the fact that we have a copy of the original consent for the estate when it was approved back in the late 1980’s. How can we avoid expensive ground investigation work?
With any planning application it is the responsibility of the applicant to provide the necessary information needed to allow an informed decision to be made.
The Local Authority and NHBC may have some information on file from the original application and even be prepared to share it with you but they are not under any obligation to do so. Extending houses can often lead to issues with foundations, particularly when building on clay or in areas with a history of unstable ground. Differential settlement through shrinkage from either the increased loading and or changes to ground-water content can take place with cracks appearing where the old meets the new. Although not entirely successful the introduction of an expansion joint along the entire junction can mitigate problems significantly by allowing a degree of movement to occur.
With regard to the ground investigation work I can only suggest you agree exactly what the planning officer wants and get quotations from reputable engineering companies for them to carry out the intrusive survey work.
Avoid going directly to companies that have a vested interest in pushing their particular expertise. For example, a piling company will push for a pile foundation solution whereas an independent engineer will put forward the best design for your circumstance. Spending a little now could save in the long run.