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Welcome to this episode of “Waterproofing Wisdom” which discusses the construction sequence of a basement.
In this episode we look at BS 8102 : 2022 Table 2:
1. Discuss the differences between the four new Grades within Table 2.
- Discuss the differences between Grades 1a and 1b.
- Discuss the confusion that seems to be present post publication between Grade 1b and Grade 2.
You can watch a 4 min video here.
Hello and welcome to waterproofing wisdom episode five my name is Ben and I am the Technical Director at CLW and waterproofing wisdom is my monthly opportunity to share with you something about waterproofing from past month which I hope you find useful.
This past month I spoke at a conference it was the 2022 International Structural Waterproofing Conference and then at the end of the day we did a panel debate and I’m there on the left and there were some other people on stage who contributed to the revision of BS 8102 which is a Protection of Below Ground Buildings Against Water Ingress and that’s a Code of Practice that’s been revised and issued this year.
It turns out there’s some confusion around Table Two which is this Grades of Waterproofing Performance and so essentially, they’re performance requirements and it’s in some ways fairly straightforward but slightly different to how it used to be and the debate was particularly around Grade 1b.
So Grade 1a allows for some seepage Grade 1b allows for some dampness and then Grade 3 is dry to me the only confusing part is Grade 2 which is waterproof but there is some condensation permissible. So those are the three grades Grade 1a seepage, Grade 1b damp and Grade 3 dry.
So what does that look like well this is Grade 1a and you can see there is some seepage there’s water ingress and both of these images are of basements where there’s water ingress and that actually isn’t compliant with this specified grade, but it’s a performance so we can look at that and say that that waterproofing performance is Grade 1a there’s some seepage it shouldn’t be and some repairs are required so there’s water ingress through cracks and things like that.
Grade 1b there shouldn’t be any seepage but there might be some damp patches and that’s what we’re looking at on screen there’s some damp patches on a concrete wall and that is suitable in various circumstances and so if we if we look in the basement and we speak to the client and they say, “oh we’re happy with some damp patches”.
We would do some due diligence on that we’d speak to the Architect and ask what finishes are required in there because often even though the client thinks some dampness is permissible, actually the finishes don’t fit that so if you’ve got plasterboard or timber in contact with the basement wall or floor then really some dampness isn’t permissible and then we’d also check in particularly with the M&E Engineers and talk about what the ingress protection rating of all the plant and equipment that’s going in there.
If it’s still true that some dampness is permissible, we might say here’s the performance specification of Grade 1b so dampness is okay seepage isn’t, now CLW we would specify that a little bit more stringently and say our maximum damp size is “xyz” but that is generally how it works.
Now how do you design for that well visit chapter nine of BS8102 and that will refer you to Eurocode 2 Part Three and Tightness Class 1 and you’d be looking at some of that content there you may also use a waterproofing additive but that’s how we would look at the Grades of Waterproofing Performance.
So Grade 1a seepage, Grade 1b Damp, Grade 3 dry and to be honest I would largely ignore Grade 2 but others may not.
So thanks for watching if that was useful to you might find a copy of our What’s new with BS8102 document helpful, it sort of summarises some of the changes and then at the end we give a whole bunch of photos of damp patches or seepage and that might be helpful to you too check in with Clients and the rest of the Design Team and say, “are we really happy with dampness?”
If you want to talk to us about anything to do with BS 8102, basement waterproofing or waterproofing design, please get in touch
Thank you very much