When additional space is required, it can often be worth exploring the opportunity of digging down to expand your premises with a basement conversion. Builders and property developers are increasingly confined with limited available and developable land, especially if the premises are within inner city areas. Basement conversions can be an attractive and far more cost-effective alternative to buying or building a new space, but they can also be massive projects to manage successfully.
Preventing water ingress
Structural waterproofing is a critical part of any below ground build or conversion project and very often, it’s the difference between success and failure. The Chartered Institute of Building states that 75% of building failure is the result of water ingress – with failures leading to mould, corrosion or other moisture-related problems such as dry rot, and even serious structural problems. For this reason, there are regulatory guidelines that professionals must follow when waterproofing.
We always recommend getting a qualified Certified Surveyor in Structural Waterproofing (CSSW) involved in any new-build or conversion project. Not only is it the best way to minimise risk, but they can help you to lever down the costs of waterproofing – which can represent a significant proportion of the total build costs. Planning early will enable your surveyor to tailor the waterproofing design to your construction type, rather than having to tailor it around other committed build considerations.
Types of waterproofing
Any below ground space that falls into Grade 3 and/or high-risk environments should use at least two different types of waterproofing systems. Types of waterproofing systems are categorised as:
Type A: This provides a barrier against ground water and water ingress by surrounding the external walls, floor and roof with a waterproof material – literally creating a barrier between water and the structure. This can be applied either internally or on the building’s exterior.
Type B: Relies upon the design and materials incorporated into the external shell of the structure itself. Structures that provide Type B protection should be constructed of reinforced water-resistant concrete or structural steel.
Type C: Involves adequately disposing of water, either by gravity, or through a sump and pump to a suitable outlet. This must be designed with adequate access points for servicing and maintenance, and a one-way valve to prevent backflow. Type C systems use a cavity allowing water to reach the drain, while being protected by an internal lining, with all joints and junctions correctly lapped and sealed.
Each has its own benefits and pitfalls. For example, while Type C waterproofing will require ongoing maintenance, it is much easier to identify and fix any problems that might arise. However, they all share one common characteristic – retro-fitting can be extremely expensive, disruptive and difficult, if not impossible in some cases.
Meeting waterproofing standards
Given the complexity of waterproofing a building, a design specialist should always be involved as early as possible. While compliance with waterproofing standards can be expensive, getting the process wrong can lead to the building’s structural integrity being compromised and therefore it will cost you far more in repair and damages. If you are unsure of what approach to waterproofing is most suited to your property then it’s always best to get in touch with the experts.
Contact our waterproofing specialists on 0808 273 2138 or complete our online contact form to find out how we can help. For more information on waterproofing and basement conversions visit: www.petercox.com.
By Mike Jones, National Waterproofing Manager at Peter Cox.
