New flat roof sealing: structure + open seams in EPDM membrane

Hello everyone,

our extension is now quite advanced, and so far everything has gone very smoothly. However, I now have some concerns regarding the construction and execution of the flat roof sealing. I am interested in your opinions on the following two questions:

1.: Construction of the flat roof sealing in the extension (cube) above the 1st floor, from bottom to top:

[*]Prefabricated concrete ceiling, reinforced according to structural engineering and poured with concrete
[*]On the concrete ceiling, a brick parapet (2 rows of bricks) on the three outer sides
[*]Primer for bitumen welding membranes
[*]Bitumen welding membranes (MOGAT Bärenhaut V60 AI S4) -> should serve as a vapor barrier or second sealing layer
[*]Unilin Utherm LE 50mm insulation boards made of PIR rigid foam 50mm -> insulation
[*]Slope insulation made of EPS Styrofoam with approximately 2% slope
[*]20mm tongue and groove OSB boards laid directly on the EPS boards (for load distribution, as the flat roof is intended to be used later as a roof terrace)
[*]RESITRIX EPDM membrane for sealing

Does this construction make sense to you? Could there be moisture problems with the OSB boards (assuming the EPDM membranes are watertight)?

2.: Processing of the EPDM sealing membranes

I was on the roof today and took a closer look at the seams. Almost everywhere, the EPDM membranes are visibly welded tightly together at the edges. However, in some places, the seams are not properly closed; at some edges, in my opinion, they are not welded together properly at all. Does anyone of you know how it is supposed to look correctly, and whether I should be worried here? I will speak to the executing tinsmith and the site manager tomorrow; possibly also have an independent third party take a look. What would be your recommendation? Please see the photos for evaluation.

Thank you very much for your support!!!

The builder

Hi!

What did your conversation with Spengler or the site manager result in today?

I am not an expert in roof waterproofing, but this does not seem correct to me.

Google the following:
Simply explained: Die RESITRIX® seam welding with the hand welding device

Watch the first video! At about 1:30 min it is said that "a very clearly visible bitumen bead of 2 to 4 mm must protrude".
I do not see that continuously here. On the resitrix homepage you will find more videos under Service.

If in doubt, you could ask the manufacturer of the membrane for their opinion in addition to an expert. They usually also have application technicians among their staff. The manufacturer has a reputation to lose and certainly has an interest in professional installation.

Regards

xray

My first welding beads looked like that too when I tried my hand on our equipment shed 10 years ago.

I would smack that right around his ears.

As it looks, the membranes are not welded but glued. To my knowledge, this is also the state of the art for EPDM membranes. The bonding is more extensive than welding. Whether the seams are really tight now, in my opinion, cannot be said like this. I covered the flat roof of a shed with such a membrane, and it also looked somewhat rough in places. However, it was the very first time I did it and it's a shed... In other words, bring it up again with the roofer and construction manager, document it, and preferably get something signed to confirm that you pointed out to them that it does not look correctly executed and possibly leaky, at least from your perspective. https://www.hausbau-forum.de/attachments/img_4223-jpg.38376/ worries me the most, it also looks to me as if the seam goes through the entire bonding.

Hello everyone,

thank you for your assessments. In the meantime, a good solution has emerged:

I contacted the manufacturer of the EPDM membrane and sent the regional field service representative the link to the pictures. At the same time, the site managers and the roofing company (who had subcontracted the tinsmith again....) immediately said that rework was necessary. As a result, there was a meeting yesterday morning with all parties involved and the EPDM manufacturer's field service representative (now that's really good service). The specialist's finding: the roof is such a mess. Proposed solution: a new, one-piece EPDM membrane of about 6 x 6 meters will be installed on the roof, custom-made by the manufacturer and with no handmade welds at all. The membrane will then be pulled up inside on the parapet using folding technique. The EPDM company that manufactures Resitrix will be present during the entire installation and will conduct training on this product for tinsmiths and the roofing company on our roof. Basically as a preference object. I’m excited – now I won’t have to worry anymore.

Regards, The annex builder

Wow, that is a really good solution!