This is a link to an article that I've just published on my blog at www.basementwaterproofingexpert.co.uk
Why Podium Deck Waterproofing Systems Fail
Example leaking podium deck.
Trace: Periodically we attend to a job like this, a basement conversion where the requirement for waterproofing was not fully understood by a general contractor, there is a lack of thought put in to design and the untrained staff installing have to do what they think best, which then results in poor detailing.
Water is unforgiving and in a wet space such as this, problems subsequently occurred. At least in this case those issues arose before completion, and we were able to step in, design an appropriate solution which we were then instructed to install.
A degree of underpinning had also been undertaken in this case, and so we advised that a Structural Engineer be instructed to advise on that aspect.
This is one example detail (membrane installed the wrong way around): 
Our client writes:
Back in Spring 2012 we decided to get our cellar converted into a much-needed extra room. We had visions of a spacious office where my wife could run her business, I could work from home occasionally, and we could reclaim our dining room from computer equipment and filing cabinets. Our “cellar” did not exist as a room, it was just an earth filled cavity under the house, but we knew it should be possible to dig down, providing the foundations were deep enough.
We had previously used a well regarded local builder for our attic and kitchen extensions, and had been very pleased with his work, so we decided to employ him for our cellar conversion too.
The work began with 3 trial holes to check the foundation depths and the state of the soil. Good news, the ground was dry, so excavation and construction started.
Spring and Summer 2012 were the wettest recorded for many years, and it rained pretty much constantly throughout all the digging, which did not help.
Things began to go awry fairly soon. Two or three streams were discovered running under our house, probably they had always been there, but unfortunately they had not been spotted in the trial holes. They were running freely so we hoped that they would not affect the cellar if they were left undisturbed.
As work went on we were concerned about the amount of water sitting under the membrane, and there were several other problems, but work was completed despite delays due to the weather and our addition of extra rooms (scope creep!). We had got as far as decorating before water started seeping in. Our builder was constantly returning to try to patch up leaks, and things came to a head when water found its way under the floor and the whole room gently rocked and pitched like a boat at sea.
At that point we decided that our existing builder couldn’t sort out the problems, and called in Trace Basements.
James Hockey, Lee Davey and his team were very helpful and we discussed several options, but as we investigated further it became obvious that there were too many things wrong to fix without starting pretty much from scratch. All of the existing work had to be stripped out, right back to the mud and concrete and bare walls. It was very depressing.
We now have a pump system installed to manage the water flows, decent drainage channels, much better membranes and seals, and are finally able to use the rooms.
Looking back on the whole process I think we were rather naive, and did not anticipate any of the problems.
Here is the advice I would give:
The finished space:
I just wrote a guest blog for the Majik House team, they installed an award winning home cinema system in a basement where we installed the waterproofing.
Head over to http://majikhouse.com/blog/article/thank-you-james
