No doubt many of our members will have seen that parts of London are once again underwater, with tube services and travel being affected across the capital. I’ve previously written that science is indicating the frequency of these events will increase, and the number of times I’ve put pen to paper on the subject certainly supports the case that further consideration needs to be given in waterproofing design.
Our regular readers of the weekly email, or those members with an interest in structural waterproofing will, hopefully, be aware that BS 8102, the ‘waterproofers bible’, is undergoing a review, and that the proposed revision is currently out for consultation.
In previous blogs I eluded to the fact that the revision might give greater thought to other sources of moisture, not just ground water, and thought I would use this opportunity to share some of the changes I have noted in the proposed revision.
The title has changed from ‘Protection of Below Ground Structures Against Water from the Ground’ to, ‘Protection of Below Ground Structures Against Water Ingress’. Perhaps this signals a changing in mindset when designing waterproofing in below ground structures…?
Scope of the standard
This change in mindset continues into the scope which now states:
‘…this standard includes guidance on the drainage outside the structure and recognises the risk of water entering a structure through openings.’
I have previously commented that during these recent flood events and based on PCA member experiences, this seems to be the most common reason why basements have flooded. So this change would seem both welcome and needed.
The changes continue into the Design philosophy where the list of external sources of water that the designer must consider has been extended to include surface and flood water:
“…strategies for dealing with all external sources of ground water, surface flood water, soil gases and contaminants should be considered from the very earliest stages of the planning and design processes for any project involving below ground structures.”
The proposed changes don’t just require the designer to consider surface water in new builds and within the inspection and survey of existing structures section. It now places greater emphasis on some of the considerations within the survey including external surface finishes and the impact this could have.
Water Resisting Design
Section 6.1 on ground water tells us that there should be consideration for the exclusion of surface water, which has not changed since the current version. But in conjunction with the other changes detailed above, hopefully this will place greater emphasis on this section.
In addition and like the current version, Section 6.3 focuses solely on the exclusion of surface water. It states that:
“where practical, provision should be made to prevent or reduce percolation of rainwater into the ground.”
Surface and Flood Water
There are rather subtle changes mainly at the front end of the document which encourage the waterproof designer to give consideration to surface and flood water. Little detail is given as to how this might be achieved, or to the implementation of these measures, but there are certainly a number of other British Standards that cover this topic which do not need to be addressed here.
I have merely reviewed the changes from the perspective of flood water and the proposed amends obviously go well beyond this. For those that want to see the proposed revision in its entirety and to provide comment, you can do so via the button below. And you don’t have long to comment on the draft consultation, as this closes on 23rd October…
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