ᐅ Undershooting the standard roof pitch? Installing a waterproof underlay
Created on: 22 Apr 2014 06:36
F
Fantamoax
Hello everyone,
We are about to sign a contract with a general contractor.
We are very pleased with the preliminary planning so far. We are planning approximately 145 m2 (1560 sq ft) without a basement. After browsing the forum and talking to architects and building experts before the planning stage, one question remains unanswered (or rather, we have received different answers).
The plan is for an asymmetrical gable roof, with one side at 30 degrees and the other at 18 degrees roof pitch.
According to the general contractor, the 18-degree pitch is not a problem, since the standard roof pitch is 22 degrees but, according to the installation plan, a membrane underlay allows for 16 degrees. However, a building savings scheme advises against this design, saying the membrane underlay is too risky and that if redesigning is still possible, it would be better to go with 22 degrees.
Initially, the installation plan convinced me, but since 22 degrees has recently been recommended again in the forum, I’m feeling a bit uncertain.
Best regards from Northern Hesse
We are about to sign a contract with a general contractor.
We are very pleased with the preliminary planning so far. We are planning approximately 145 m2 (1560 sq ft) without a basement. After browsing the forum and talking to architects and building experts before the planning stage, one question remains unanswered (or rather, we have received different answers).
The plan is for an asymmetrical gable roof, with one side at 30 degrees and the other at 18 degrees roof pitch.
According to the general contractor, the 18-degree pitch is not a problem, since the standard roof pitch is 22 degrees but, according to the installation plan, a membrane underlay allows for 16 degrees. However, a building savings scheme advises against this design, saying the membrane underlay is too risky and that if redesigning is still possible, it would be better to go with 22 degrees.
Initially, the installation plan convinced me, but since 22 degrees has recently been recommended again in the forum, I’m feeling a bit uncertain.
Best regards from Northern Hesse
B
Bauexperte22 Apr 2014 08:17Hello,
**Standard roof pitch (SRP) is the minimum roof slope limit, depending on the material, at which a roof covering has proven to be weatherproof in practice.
The **underlay membrane (ULM) is a special additional measure to ensure weather protection under roof coverings. It is thus part of the building envelope and serves as an external seal or wind barrier on the outside.
**This is explained so well in Wissen-Wiki that I have adopted their definition.
As long as the requirements for construction below the SRP are observed by your general contractor (GC), there is nothing against a pitched roof with varying roof slopes (RS). I am sure your GC has done this before; furthermore, they provide a warranty for it, so why would they advise against it if they expect problems?
PS: I referred to 22° regarding the additional costs. Between 22 and 10/12°, the roofing must, among other things, be fastened with clips.
Regards, Bauexperte
Fantamoax schrieb:An expert from the Builders’ Protection Association?
On the other hand, a building savings contract advises against this plan. A breather membrane would be too unreliable; if you can still redesign, better go for 22 degrees.
**Standard roof pitch (SRP) is the minimum roof slope limit, depending on the material, at which a roof covering has proven to be weatherproof in practice.
The **underlay membrane (ULM) is a special additional measure to ensure weather protection under roof coverings. It is thus part of the building envelope and serves as an external seal or wind barrier on the outside.
**This is explained so well in Wissen-Wiki that I have adopted their definition.
As long as the requirements for construction below the SRP are observed by your general contractor (GC), there is nothing against a pitched roof with varying roof slopes (RS). I am sure your GC has done this before; furthermore, they provide a warranty for it, so why would they advise against it if they expect problems?
PS: I referred to 22° regarding the additional costs. Between 22 and 10/12°, the roofing must, among other things, be fastened with clips.
Regards, Bauexperte
Thank you for the quick response, construction expert!
That’s correct, the home savings contract is from the Building Protection Association.
Regarding the statement about the home savings contract: "Do you know what such an underlay looks like after 20 years?..."
I was aware that the breathable roofing underlay is an additional measure. I directly addressed this with the general contractor, and he told me that he generally uses it, even with steeper slopes. The general contractor definitely has experience with this roof pitch. You are right; he also has a corresponding warranty obligation. The tile manufacturer specifies the lower pitch with breathable underlay as well (down to 6°). The general contractor had already reassured me about my concerns.
Unfortunately, I misunderstood you in the neighboring post? And suddenly it was back to... So now you prefer 22 degrees after all.
As I said, thanks for your help. We will proceed with 18 degrees since we also prefer the appearance.
That’s correct, the home savings contract is from the Building Protection Association.
Regarding the statement about the home savings contract: "Do you know what such an underlay looks like after 20 years?..."
I was aware that the breathable roofing underlay is an additional measure. I directly addressed this with the general contractor, and he told me that he generally uses it, even with steeper slopes. The general contractor definitely has experience with this roof pitch. You are right; he also has a corresponding warranty obligation. The tile manufacturer specifies the lower pitch with breathable underlay as well (down to 6°). The general contractor had already reassured me about my concerns.
Unfortunately, I misunderstood you in the neighboring post? And suddenly it was back to... So now you prefer 22 degrees after all.
As I said, thanks for your help. We will proceed with 18 degrees since we also prefer the appearance.
B
Bauexperte22 Apr 2014 09:50Hello,
Regards, Bauexperte
Fantamoax schrieb:This once again confirms my previous impression
Correct, the home savings contract is from the Homeowners’ Protection Association
Regards, Bauexperte
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