Should I redo the flat roof or can I fix the mistakes?
We have doubts about the quality of our flat roof.
1. installation of roofing membranes
As you can see in the two photos below, the manufacturer's instructions were not followed correctly. On one hand, the underlayment was tucked directly to the wall, and on the other hand, it was not done twice at the joints. According to the sample sketch, the corner should have 4 layers on top of each other, and we only had 2. Also, the height of the bottom sheet is not the same as the height of the top sheet, which means that only the bottom sheet is prevented from slipping by the subsequent strip of cover. In addition, the ice wedge was not installed.
2. connections at the parapet.
Same problem with the connections at the parapet. Also, the top layer was only laid to the end of the parapet, not to the outer edge as shown in the sketch. In our opinion, water can get under the metal covering due to rain or snow drifts, and therefore sooner or later through the joints.
3. pimple formation on bitumen sheeting
You may also notice that pimples are slow to form on membranes where there is a lot of sunlight on them. We have been told that some manufacturing errors were made and this could lead to this formation. Our assumption is more that moisture has already collected in the insulation underneath, which then tries to dissipate outward by sunlight. Has anyone had a similar experience? Opening the lid would reveal residual moisture in certain places anyway, but it would dry out after a short period of standing.
4. sleeve cap.
Also, the photos below show that the masonry is exposed in places and not completely covered by the cladding tape. This is probably related to my first point, since the courses were not in two pieces. Instead, just in case, the entire course was drawn from left to right. Also, it is not entirely clear to me how the current design is supposed to prevent water from entering the plaster behind the cover rail. According to the sketch, the cover rail should be recessed into the masonry so that water doesn't get behind it.
As a solution, the roofer suggested we put another membrane on top of the existing membrane to make up for the lack of material from item 3 and to cover other deficiencies. From our perspective, this is a lot of chutzpah, as we believe the defects still exist and will only be covered by another layer. What are your thoughts on this? Does it make sense or should we insist on redoing the entire roof?
You won't like the answer:
After years of difficult experience with roofing felt (aka bituminous membrane), I see here the typical problems:
-flat laid membranes will eventually leak because the welding/adhesive seams will
tear. If there are puddles standing on it, water will get in at some point.
— Surfaces that can be walked on are at special risk. At some point someone will put a chair on it and make holes in it.
If it were possible, I would
— Slightly tilt the floor
— Put a hard top layer on it or at least block access.
Even with proper installation, these are typical problems with bituminous membranes.