New Build Basement waterproofing
When constructing a new basement, either as a “stand alone” property, or as an addition to an existing property, it is vitally important to design the waterproofing system before works commence. We refer to it as a system because that’s exactly what it is – a combination of products, incorporated into, and onto the structure, installed in the correct sequence, by a competent person.
It is therefore essential that the design is given the respect it undoubtedly deserves, as overlooking what may appear to be a minor detail, can result in a major problem. Even when the design and products themselves are considered suitable for the intended purpose, failure to understand the importance of the correct installation procedures can result in dampness and water ingress. After all, the last thing anyone wants is to invest so much time and money into the project for it to fail!
What is the solution?
Once the decision has been made to construct a new property or extension, with a basement, the usual procedure is to employ an Architect to design it. The Architect will then engage the services of a Structural Engineer to design the structural elements. It is also likely that they will obtain a Ground Survey to establish the ground conditions. It therefore makes perfect sense to employ a suitably qualified and experienced Structural Waterproofing Designer.
The designer will follow the guidelines within the relevant British Standard – BS 8102:2009 the “Code of Practice for Protection of Below Ground Structures Against Water from the Ground”.
Elite Basements have the required qualifications and experience to design and install your Structural Waterproofing System. Please contact us for further information. There are 3 different types of systems – click here to take you to our Structural Waterproofing Page.
External Drainage in New Construction
It is important to install a ‘properly designed and maintainable land drain’ around the external perimeter of the basement.
The drain serves 2 purposes.
1. On the plans the drain will be shown. In the notes the structural engineer will detail the design of the structure – the type of reinforcing within the concrete, and the specification of the concrete itself. It will sometimes say that the structure has been designed “without water pressure”
2. As far as waterproofing is concerned the guidance of B.S.8102:2009 the “Code of Practice for Protection of Below Ground Structures Against Water from the Ground”, advises that the design:
a) Should allow for less than perfect workmanship.
b) Be aware that the products/system may have defects.
We know that if there are any defects in ‘a’ or ‘b’, and that if water pressure comes to bear on the waterproofing system, then water ingress can occur. Therefore the waterproofing design is also designed “without water pressure”
However in order to ensure water pressure does not come to bear on the waterproofing the drain needs to be placed in a lower position – close to the bottom of the ground bearing floor slab.
The structural engineer when designing the construction may not be aware of the type of waterproofing system to be used, and will possibly have designed his land drain purely to satisfy his own design criteria.
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