Is it ok to use more then four nails per shingle?

Answer 1

This is base on strenght of the roofing shingle material and the expected wind velocity. Most asphalt singles are rated for a given wind speed - such as 75 mph or 100 mph. The manufacturer of the shingle specifies the number of nails and the placement of the nails to yield the resistance to lifting and tearing of the shingle for the specified wind. If the manufacturer states that to attain the guaranteed performance you need to use 5 nails per shingle, you should use at least 5. You may use more but the placement of the nails will not be according to the manufacturer recommendations so will probably void the grantee. Some laminated shingles may be rated for 125 mph with 6 nails per shingle if the nailing pattern complies with their specifications. Since the lifting of a shingle tab is not related to the number of nails, additional nails will not prevent a tab from lifting and tearing off. The number of nails will however affect the tendency of the wind lifting the entire shingle, then a section of shingles, and ultimately the entire layer of shingles. The lifting of a tab is more related to the sealing of the tab to the shingle below it which should be attached with the correct number of nails. A shingle tab seals to the shingle below by being heated by the sun till the patch of tar on the underside softens till it sticks to the lower shingle. Properly sealed, the entire roof surface acts like one continuous sheet of roofing. Since a strong wind may create a lifting force on that entire sheet, the proper number of nails is important, but also is the condition of the roof sheathing - whether it be plywood, waferboard(OSB), or

lumber(1 x 8 or such). Adequate nails into rotten wood still makes for a roof that will blow off the house.