There are two main reasons.
Standing seam metal roof installation details.
Unlike steel and aluminum shingles standing seam panels should not be installed over the existing asphalt shingles.
The connecting point where the two separate metal panels meet forms a vertically pointed rib or a seam that is one inch to inch and a half high.
First of all if you install a standing seam metal roof over asphalt shingles there will be a so called telegraphing effect where shingles can punch horizontal lines in standing seam panels.
For do it yourself enthusiasts for your first installation we recommend installing standing seam on a simple gable roof with minimum roof penetrations.
Standing seam roofing is particularly noted for its use of hidden fasteners.
From underlayment venting layout.
Applicability the metal roof system as described within this manual is classified as a standing seam metal roof panel.
For nail strip panels one pancake screw is required every 12 24 inches depending on wind requirements.
If you have chimneys skylights dormers and or valleys on your roof we recommend you leave this task to a seasoned professional installer because it s really easy to make costly mistakes when installing metal flashing and other details.
Step by step instruction on how to install a standing seam metal roof.
Pancake screws are used because they are strong and yet have a low profile that does not interfere with panel and trim installation.