ᐅ Roof Terrace – Waterproofing Beneath the Screed

Hello everyone,

My wife and I had a roof terrace built over our garage. In total, three companies were involved in the project. The terrace is sloped towards the center with a drain and an emergency overflow.

Here is the problem: the terrace was sealed on top with a vapor-tight waterproofing layer. In the area around the drain, bubbles formed. We contacted the company that installed the top waterproofing. The bubbles were cut open, and moisture was found in the screed. We informed the company that installed the drain about this situation, as it was suspected that the drain might be leaking. The area around the drain was opened up, and a new drain was installed a few days later. The company covered the exposed area with plastic sheeting and aluminum tape to prevent moisture from entering the opening. Afterwards, a leak test was carried out.

Next, the screed installer, who also originally installed the screed, was brought in. The open hole was filled with epoxy resin. We asked the screed installer whether the resin was waterproof or if the area needed to be sealed, since the company responsible for the top waterproofing would have time in the following days. We were told that the resin would harden in two hours and cure fully in 24 hours. It was very warm on those days, and the resin was hard by the next day. After a few days, it rained overnight and for half the day. My wife noticed a water stain appearing in the stairwell. The stain kept growing. The stairwell adjoins the roof terrace. We have also now noticed a damp area in the heating room. We immediately suspected that the epoxy resin was not waterproof after all.

We asked a screed installer friend of ours for advice. The specialist company that installed the screed on the terrace did not apply any waterproofing beneath the screed. Our invoice states that waterproofing was installed. Together with our friend, I reviewed the photos I took during the screed installation. The company simply laid a bitumen sheet (Erika or Katja) under the screed and then placed a thin polyethylene sheet on top before installing the screed. That can hardly be considered proper waterproofing for a terrace, can it? We called the company and explained the situation. So far, they do not acknowledge any responsibility. Yesterday, I sent the company a formal complaint by registered mail.

My questions are as follows:

I think the company has two options: repair (remove screed, apply waterproofing, reinstall screed) or refund the money and restore the original condition. But who will reimburse us for the top waterproofing? Around 15,000 EUR (about 16,000 USD) has been invested in that. I assume this will lead to a legal dispute. What are the chances of winning such a case?

Thanks in advance for your advice.

Isn't your problem more likely above the screed? I mean, the screed itself is not "water-bearing," so the waterproofing should probably be applied from above, right?