In this blog, Icon Surveyors will first consider what is a "Slip Membrane" and why it is used. Thereafter, we will look at the differing situations in which they are utilised.
In simple terms,
There are many different types of "Membrane" used in construction. However, "Slip Membranes" are generally used to separate sliding joints that are created between concrete surfaces. These can be found when building foundations or between surfaces where concrete and/or brickwork is used. The latter of which may be within roof slabs or supporting walls. "Slip Membranes" come in different sizes and materials depending on their usage.
For the purposes of this blog, Icon Surveyors will concentrate its efforts on the use of a "Slip Membrane" when building foundations for an extension. The primary purpose of a "Slip Membrane" when laying a foundation is to enable slight movement between any existing building and the new extension, thus preventing any bonding between the buildings which may in turn cause either cracks to appear or separation of the structures.
When digging the ground to build foundations for a new construction to be placed on top of them, over a period of time, there will usually be some form of settlement occurring in the ground. For this reason, "Slip Membrane" is used to enable settlement to occur over the whole of the new foundation thereby minimalizing any future problems that may arise from such settlement.
Icon Surveyors would always recommend the use of "Slip Membrane" to any building owner intending to build an extension. As stated above, it is used primarily to prevent any cracks or separation occurring as a result of any settlement that may arise from digging the new footings. That is not to say that any settlement that may occur is guaranteed to cause any future damage, however, the likelihood of settlement causing cracks and/or separation, in our experience, is more likely than not.
Icon Surveyors believe that prevention is better than cure! "Slip Membrane" is relatively cheap when considering how much a building owner is likely to be spend on the concrete used to fill the footings. In consideration of the low cost of using "Slip Membrane" and making good once any settlement has stopped, in comparison to costs that would be incurred for any major damage that may arise as a result of not using it, as stated above, Icon Surveyors would always recommend that "Slip Membrane" be used.
Icon Surveyors are happy to provide a free party wall advice to any building or adjoining owners who may be affected by the subject matter raised in this blog.
Note*: This blog is not an authoritative interpretation of the law; it is intended as a general guide.