Metal roof/ ridge vs flat
 

I'm considering a new metal roof on the house(it currently has shingles) and notice that the latest trend is to nail or screw the roof in the flat instead of the ridge. I don't think this makes sense if you plan to keep the roof as long as the metal will last.

I asked a roofer to explain why the flat is the best he gave some reason that I don't remember. I asked what happens when the rubber washer rots from around the screw and he said, "Well, it will probably be time for a new roof." I thought, are you kidding? There is no time for a "new" metal roof unless it is damaged. We have metal roofs on our barns that have been there for 50 years, all nailed in the ridge. All they need is a coat of paint about every 8-10 years. For some unknown reason, there are a few random nails in the flats, and those are the places that give leak problems.

My theory is this: Nailing in the flat is quicker and, therefore, better for the installer. For support, some idea has been developed as to why screwing in the flat is better, but i don't buy it. It might be possible that it will last as long as people will "want" the roof. I realize that people these days replace things long before they "need" replacing just because they want something different.

But, if I want the roof as long as the metal will last, which will be years and years, wouldn't putting screws in the ridge make more sense?

The rule of thumb is to nail through the top of the rib and screw on the flat. Screws pull down tight and can cause the ribs to dent. A screw will seal better to a smooth surface. The neoprene washers will fail in about 7-12 years and can be replaced with bigger screws. Screw down panels are not meant for application on residences, they are meant for agricultural installations (barns).

If you must use exposed fastener panels on your house be sure to use a quality, high temp underlayment like Tamko Metal and Tile. Its a peel and stick membrane similar to Weather Watch with a high melt point.

Also..why do you equate quicker with better. Screws hold a lot better than nails, even ring shank nails.

I meant that "quicker" was better for the contractor putting it on. faster means more money for him.

I agree, time is money in the construction trades. When we put on screw down panels we first mark on a panel a line where all the screws will go, then lay that panel on top of the stack of full sheets. Then we predrill all the full sheets at the same time. This saves a LOT of time on installation and keeps all the screw heads in a uniform, straight line.

Once again, if you go with screw down panels, I cannot suggest strongly enough to invest in a quality underlayment made for metal roof installation...and be sure if you presently have shingles to remove them prior to application of the metal. I see a lot of installers save time by installing a wooden batten and going over the shingles that are on the roof. This will severely shorten the lifespan of the metal roof installation. Trapped air will cause condensation and the moisture will rot the battens. You want the metal in contact with a hard surface not installed over an airspace.

This post may be a wee late but if i may add my 2 cents. Most roofing tin is designed either with a hidden fastening system or a rib fastened method. Screwing in the field or flat is okay in a siding installation but roofing is meant to be fastened at the rib for ultimate strength. If wind gets under the sheets it can be torn off quite easily when fastened in the flat. The ribs add rigidity to the steel hence fastening here is recommended. Also any warranty may be void if fastened incorrectly or with improper fasteners