ᐅ Flat roof leaking: repair or build a pitched roof structure over it?
Created on: 11 Feb 2021 06:58
R
Rolexianer
The flat roof on the wooden decking of a 55-year-old single-family house is leaking. Rainwater drains through seepage pipes inside the house. I suspect the cause of the leak is at one of these seepage pipes, as discoloration can be seen on the ceiling of the upper floor about 1.5m (5 feet) away from it. This issue was already addressed by professionals eight years ago, with stones removed locally and a membrane installed.
To avoid another limited repair, I would prefer to take decisive action and add a low pitched roof on top, similar to the neighboring house. This would direct rainwater to the outside, which is an advantage, as the downpipes can also show leaks at the basement access covers.
The carpenter has already visited and estimated the costs at €40,000 plus VAT (house dimensions 7 x 13m (23 x 43 feet)). The earliest possible execution date he can offer is August. A meeting at the local building authority is planned soon to discuss the project roughly, for example regarding a gable roof, shed roof, roof overhang, etc. Afterwards, a concrete quote could be prepared and an architect (recommended by the carpenter) involved. The building authority will likely prefer a gable roof, since that is visible on the neighboring house.
I am concerned about the house’s structural stability since a gable roof would add load to the center of the building, while the main load-bearing wall along the longitudinal axis is located about 1.5m (5 feet) off-center. This will need to be calculated by a structural engineer and likely cannot be ideal.
Another issue is that after adding a roof truss, the current flat roof assembly will probably become difficult to access if repairs are needed in the future.
Am I heading in the right direction? Is adding a roof truss really a worry-free solution, as the carpenter claims?
Perhaps I should just carry out a comprehensive renovation of the flat roof, probably at about half the cost of the carpenter’s proposal, but then it will likely leak again at some point.
Which solution should be aimed for? What else should I keep in mind?
To avoid another limited repair, I would prefer to take decisive action and add a low pitched roof on top, similar to the neighboring house. This would direct rainwater to the outside, which is an advantage, as the downpipes can also show leaks at the basement access covers.
The carpenter has already visited and estimated the costs at €40,000 plus VAT (house dimensions 7 x 13m (23 x 43 feet)). The earliest possible execution date he can offer is August. A meeting at the local building authority is planned soon to discuss the project roughly, for example regarding a gable roof, shed roof, roof overhang, etc. Afterwards, a concrete quote could be prepared and an architect (recommended by the carpenter) involved. The building authority will likely prefer a gable roof, since that is visible on the neighboring house.
I am concerned about the house’s structural stability since a gable roof would add load to the center of the building, while the main load-bearing wall along the longitudinal axis is located about 1.5m (5 feet) off-center. This will need to be calculated by a structural engineer and likely cannot be ideal.
Another issue is that after adding a roof truss, the current flat roof assembly will probably become difficult to access if repairs are needed in the future.
Am I heading in the right direction? Is adding a roof truss really a worry-free solution, as the carpenter claims?
Perhaps I should just carry out a comprehensive renovation of the flat roof, probably at about half the cost of the carpenter’s proposal, but then it will likely leak again at some point.
Which solution should be aimed for? What else should I keep in mind?
11ant schrieb:
Does it have to be cold-applied adhesive because otherwise the insulation board would get damaged?Yes, it is cold self-adhesive; the protective film is peeled off and it sticks immediately. When the top layer is welded, the cold self-adhesive membrane is exposed to heat again, which makes it bond even more firmly to the insulation.The roll measures 1000 mm x 3 mm x 10 m (40 inches x 0.1 inches x 33 feet) and consists of top-quality elastomeric bitumen with a glass fiber and polyester fleece reinforcement, cold self-adhesive.
A secure seam connection is ensured by a removable longitudinal edge strip.
Bitumen is bonded to bitumen.
It can be directly installed on Thermazone EPS and Thermazone PIR aluminum foil insulation boards.
Proven effective for over 30 years.
Price is approximately 6–7 euros per square meter (about 0.56–0.65 USD per square foot).
Alternatively, at least one PYE Photovoltaic 200S5 welded membrane should be applied (welded), and the roof will be watertight. A small tip: not all welded membranes are the same; there are differences in composition, materials, and thickness, for example, 5 mm and 5.2 mm (0.2 inches) thickness, carrier reinforcement, bitumen quality, etc. The price per square meter ranges from 7.00 to 18.00 euros (about 0.65 to 1.67 USD per square foot) for welded membranes.
icandoit schrieb:
440 euros per m2 is extortionate. What exactly are you paying 440 euros for? What materials and labor are included in that price per 1sqm (square meter)?
Prices for materials:
Primer coat (VA) 30 liters is enough for about 100sqm (1080 sq ft), costs around 30-40 euros. Quality varies by manufacturer.
Vapor barrier welding membrane costs about 5-10 euros per sqm (varies with manufacturer quality), thickness ranges from 2mm to 4mm (0.08–0.16 inches).
Flat roof insulation boards minimum thickness 160mm (6.3 inches), ideally 240mm (9.4 inches), price per sqm ranges from 25 to 45 euros, depending on manufacturer and quality.
Self-adhesive (welding) roofing membrane applied on the insulation costs 6-8 euros per sqm.
Top layer welding membrane, at least a PYE Photovoltaic 200S5, better quality membranes cost up to three times as much; price per sqm is 7-18 euros, depending on manufacturer and quality.
Now calculate yourself what just the basic materials cost per sqm.
If you only buy high-quality materials, you can quickly spend twice as much.
I sealed my entire roof, 120sqm (1290 sq ft), myself using the best quality materials, including fascia boards, wood, gutters, etc., and spent 10,000 euros on materials alone.
R
Rolexianer13 Feb 2021 18:47caspar.1 schrieb:
What is the 440 euro payment for?The house is located near Munich, which probably plays a role. The carpenter could start the work at the earliest in August.Regardless of the carpenter, I have contacted the tradesperson with the best reputation for flat roof renovation; the waiting time for the work to be carried out is two years.
R
Rolexianer13 Feb 2021 18:55icandoit schrieb:
Just putting a pitched roof on it? Architecturally, I don’t think it’s that simple. It somehow doesn’t suit the house.I am also a bit concerned about the appearance, but what matters most is what helps me sleep better.The rainwater would then drain outside, which is an advantage since the downspouts already showed leaks around the access hatch in the basement. Admittedly, that can be fixed, but it remains a potential problem area. I prefer the rainwater to be managed outside.
A conversation with a roofer is scheduled... I am open to solutions...
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