Why don’t they use washers under the head of the screw to give move movement for expansion and contraction and a greater surface area of hold down coverage?
Keep in mind that even if you provide a washer, which may help, you still have the screw shaft and it only has minimal clearances on it's left and right, i.e. the panel nail flange hole width.
Are all the conditions listed for nail strip the AND-conditions or the OR-conditions. For example, if I live in a country that is cold in winter and hot in summer but the roof length is only 12 feet. Is nail strip panel good for this?
David, Nail strip is still an expensive panel and it's not nearly as weather-tight as a snap lock system. My suggestion would be to spend a little extra and use a snaplock system with clips. That way you don't have fasteners penetrating the panel. It will also do better with expansion and contraction
Why don’t they use washers under the head of the screw to give move movement for expansion and contraction and a greater surface area of hold down coverage?
Keep in mind that even if you provide a washer, which may help, you still have the screw shaft and it only has minimal clearances on it's left and right, i.e. the panel nail flange hole width.
Are all the conditions listed for nail strip the AND-conditions or the OR-conditions. For example, if I live in a country that is cold in winter and hot in summer but the roof length is only 12 feet. Is nail strip panel good for this?
David, Nail strip is still an expensive panel and it's not nearly as weather-tight as a snap lock system. My suggestion would be to spend a little extra and use a snaplock system with clips. That way you don't have fasteners penetrating the panel. It will also do better with expansion and contraction