Waterproofing and Damp Proofing Consultants

Legal Case: Steuerman -v- Dampcoursing

A recent court ruling has highlighted just how vulnerable specialist companies can be when they include in their system work done by others, when that work is an essential part of the efficacy of the system.


Jean Louis Steuerman is a concert pianist who had an extension built by a contractor. This extension was partly below ground level, and was waterproofed using Bituthene bonded sheet membrane (Figure 1).

Groundwater pressure came to bear against the membrane, and it leaked!

The engineer responsible for the design, and the main contractor, agreed to engage the services of a specialist contractor for advice regarding remedial work, and they approached Dampcorsing Ltd, who recommended the installation of a cavity drainage system.

The design principle was agreed, and Dampcorsing quoted to install the membrane after the contractor had removed the lower part of the internal load bearing walls and installed a drainage outlet at an agreed point in the basement (Figure 2).

The construction of the basement was such that the internal load bearing wall had to be propped, which meant that Dampcorsing needed to install the membrane in two parts – the first to the lower part of the walls and a small section on the floor (Figure 3). The second part included installing the remaining membrane across the floor, after the main contractor had rebuilt the lower part of the wall (Figure 4).

The work all went according to plan, and the basement was completed and handed over to the client.

All was well for about twelve months, but then some dampness appeared on the floor. Limited exposure was undertaken, and it was established that the outlet drain had become blocked by an unknown substance. This blockage was rodded clear, but the problem returned soon after.

A dispute arose as to who was responsible for the blockage of the drainage system, and Mr Steuerman engaged the services of an architect who arranged for remedial work to be undertaken. He then sued Dampcorsing for the cost of the remedial work, as well as various other costs he had incurred.

The Technical Issues

The remedial work was supervised by Ray James, a building surveyor engaged by Mr Steuerman, who also acted as his expert in court.

As the remedial work had been completed before he was engaged, the author did not have the advantage of seeing the drainage when the floor membrane was lifted. He had to rely on the information given to him by Mr James - who was present, but did not specifically note what was causing the blockage to the outlet.

Both experts agreed that the cause of the persistent dampness in the basement had to be as a result of blockage of the drainage outlet - what they disagreed on was the most likely cause.

Mr James said it was because Dampcorsing did not flood test the floor prior to laying the membrane. The author, acting as expert witness for Dampcorsing, argued that there was no proof that the failure to flood test the floors was the cause of the blockage. Indeed, Mr James had reported that when the membrane was lifted and the outlet cleared, the water ran out leaving 10 – 15mm deep puddles on the floor. The author argued that since the membrane used had a 20mm stud, this would have left 5mm for water flow – more than enough in the circumstances.

The author argued that a more likely cause for the blockage was debris kicked under the “tail” of the floor membrane during construction of the load bearing wall. This debris could then have worked its way to the outlet, causing a backup of water resulting in lime building up and cementing the debris, causing the blockage.

The Legal Argument

Counsel for Dampcorsing argued that Mr Steuerman’s representatives had removed all the evidence as to the cause of the blockage, and had not shown why the blockage occurred. They argued further that Dampcorsing’s expert had shown a possible mechanism of blockage that was caused by debris being kicked under the tail of the floor membrane around the edge by the Main Contractor, and surely Dampcorsing could not be held responsible for that?

Counsel for Mr Steuerman argued that they felt the failure was as a result of Dampcorsing not undertaking sufficient care in testing the drainage before putting the membrane down. They argued that, despite the fact that the Main Contractor had installed the drainage, as specialists Dampcorsing had a duty of care to ensure the work done (i.e. the drainage) by the Main Contractor was adequate.

The Judgement

The Court found in favour of Mr Steuerman in all respects. In his judgement, the Judge accepted that the arguments propounded by both experts were possible. He also accepted that it was not possible for them to be certain of the cause of blockage, as the evidence had been destroyed when the remedial work was completed and so any theory as to the cause of blockage was just that - theory.

However, he found that the cause of the blockage was not relevant, as the client had engaged the services of a specialist company to provide him with a dry basement, and in this they had not been successful. He accepted the drainage was an essential part of the system, but the fact that the Main Contractor undertook this important aspect of the contract did not absolve Dampcorsing of liability. The drainage was in place when they took over the site to install the membrane, and should have advised the contractor if they considered it to be inadequate – they did not, and so implicitly accepted the drainage as being adequate.


This case highlights that where certain aspects of a waterproofing system are undertaken by others, the specialist company can (and probably will), be held liable for those aspects if they are considered to be an essential part of the system.

Examples (by no means exhaustive) of other situations where a specialist contractor could be found liable for the workmanship of others include:

1. When he applies cavity drain membrane to walls prepared by others, and the drainage becomes ineffective because of old renders/plasters/timbers falling and blocking the cavity.

2. When he applies waterproof renders to a substrate prepared by others.

3. When he applies waterproof cementitious coatings to a render basecoat applied by others.

However, it is unlikely that a specialist waterproofing contractor could be held liable for the workmanship of others if they are specialists in their own right. For example, if a specialist pumping contractor installs the pumping system, it would be unreasonable for the Courts to expect the waterproofing contractor to have to accept liability for that company’s workmanship.

Or would it? When it comes to Court Judgements, nothing is certain!

The Lesson

Since the specialist waterproofing contractor is likely to be held liable for all (or most) aspects of a waterproofing installation, it makes sense for him to insist that he undertakes all the relevant work – it does not make sense to allow somebody else to get paid for doing bad work, when he (the specialist) is going to have to accept responsibility for that work, but does not get any of the profit.


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