Basement Structural Warranty and Basement Waterproofing Insurance Backed Guarantee

Not to be confused with my guarantee, contractor guarantees, or product certification. They are dealt with on another page. Link opens in a new tab. This page explains What to expect, and what you shouldn't expect, from a Structural Warranty. What to expect, and what you shouldn't expect, from an Insurance Backed Guarantee. IBG. A Structural Warranty is an insurance policy for your new dwelling that a lender wants to see is in place before they release funds if the property is less that 10 years since completion. Because lenders don't know about building. A structural Warranty Provider is an insurance broker who arranges the warranty insurance and, to make that insurance as profitable as possible, arranges or checks that every item covered by the Warranty is covered first by another insurance policy, an IBG. The IBG is covered by a personal or company guarantee. If there is a failure, the installer is called upon to correct it. If they cannot be made to fix it, the IBG is called upon. If, somehow, the installer and the IBG both fail to put the problem right, and if it is covered by the structural warranty, then the structural warranty is called upon. You pay for insurance twice. And both insurances are re-insured again by the installer. But beneath ground waterproofing is excluded from every structural warranty policy. Despite that, it has been normal - for years - for someone to demand that you get an IBG for basement waterproofing. And the ONLY newly built domestic basements to have leaked over the past 10 years did so because they had an IBG for an internal drainage system in the basement. By insisting on an IBG for basement waterproofing, these same people have chosen to completely ignore the legal requirement to comply with the relevant building regulation. Building Regulation C2 states "The walls, floors and roof of the building shall adequately protect the building and people who use the building from harmful effects caused by (a) ground moisture". These brokers, and the surveyors they employ, and even some local authority building inspectors, have been the bane of my working life for 15 years. They allow leaks because they followed, and still follow, the then current Approved Document: BS8102:2009. That document was largely written by the firms that sell internal drainage systems, including Maclennan and Newton. "Pumping out water is a no-brainer" they said. I got nowhere with this battle while BS8102:2009 was the Approved Document. I tried to explain so many times, if you are allowed to leave leaks, worse leaks will be left as each workforce gets its next project, because they still get paid and they make more money cutting more corners. But worse leaks let in mud. Mud blocked pumps, When it continued to rain, the basement flooded. There was mould. There was illness (harmful effect), and the law, building regulation C2, not complied with.

STOP PRESS A recent ruling, May 2025, by the Supreme Court held that a designer that made a bad decision, many years earlier, while working for Barratt Homes, that resulted in repairs many years later, is responsible for the cost of those repairs. This would be a powerful legal precedent for anyone you know to now use if their designer or warranty provider insisted on internal drainage, the basement contractor left leaks, and their basement later flooded because the pumps were blocked by mud. And they found that none of their insurances helped in any way with the damage and suffering. The court report is here but this might be too dry to wade through. This analysis by Blackstone Chambers might be a lot easier URS Corporation Ltd v BDW Trading Ltd. 22nd May 2025

STOP PRESS. SELF BUILD ZONE. June 28th 2025 a client sent me this extract from the warranty they have brought. his email expressed his concern, presumably about the basement waterproofing, that if they did not have a basement IBG, they would not be able to sell if the warranty was not complete. This does not say that either membrane or tanking must be fitted. But it does say "secure the waterproof envelope". What is 'the waterproof envelope'?. Follow this link, then the first link to Self Build Zone, then find page 9. Near the bottom. " excluding those parts below ground floor slab level." The client says that he has not been asked for a basement IBG. Perhaps we can add Self Build Zone to Protek and BW who don't need re-insurance for what they don't themselves insure.

Another favourite diversion, by warranty providers and private building control bodies, is to try to claim that every word throughout BS8102:2022 applies to this project. That has to be nonsense. Here is one reason why: Your project is a new domestic basement yet to get the house on top. BS 8102:2022 Protection of below ground structures against water ingress - Code of practice applies to all below ground structures.   If this web site is of interest, your project is not about a Victorian cellar conversion, or going under something already there, or commercial.     The Standard explains that a relevant path needs to be found through it. And the most obvious and appropriate, for a new domestic basement, is no leaks or damp patches.

When you get told you must have an insurance backed guarantee, IBG, immediately write a letter or email to that person. Put the conversation on record. Include or attach the letter from DLUHC and point out that if they want you to depart from BS8102:2022, by insisting upon internal drainage when Table 2 and 3.16 of the Standard does not want it in Grade 3 accommodation, then they are legally responsible for all the consequences, damages and costs.   Click on these two images to view and save the originals and attach them to your email     Include in your letter, perhaps as enclosures, links or attachments, my web pages about the new laws and procedures, and perhaps this page as well. You may have to write this to The architect The structural warranty provider The building regulation control body

Explain, first of all, that as far as you have been able to find out, their insisting on an IBG means that they (architect/insurer/inspector) are insisting on a departure from BS8102:2022 known to fail and likely to incentivise or cause the leaving of leaks. Leaks cannot all be identified and fixed until after the structure is completely weathertight, it has been cleaned and dried, and inspected before anything covers the basement inside. Because it fills up with rain and muck as soon as the wall formwork is put up. Be in no doubt. If you have a quote from a CSSW that his company will paint or seal the concrete first, it excludes leaks. Leaks are very difficult to fix when water is coming in toward you, pushing your repair off before it sets and cures. Mention that some leaks won't be identifiable when you complete your work and won't ever be identified if they insist they are covered over - unless and until the causes of later flood damage and ill health are investigated. Put it on record that if the basement leaks at any time in the future, that you will blame them. You will have their correspondence and lots of photos. You or the client will sue them, perhaps the Building Safety Regulator will prosecute them. And make it clear what is not covered by the IBG (only IDS labour and materials are covered with nothing for the structure) and the client will win damages.