Where to screw down 5V roofing

[LarryD]

I don't think you can go wrong following the manufacturers instructions.

I requested quotes many years ago to replace the three tab roofing on the house with architectual shingles. I had lost parts of shingles to high winds.

While the estimators were measuring and making notes I would ask questions about products and warrantees but always managed to get them to detail nailing proceedures. All three contractors recommended the same brand (local favorite) but only one had the right answers for storm nailing the south side (predominant high winds) and normal pattern for the north side. One guy even described their staple method which the manufacturer had no proceedures for. The winning bid wasn't the lowest but it looks as good today as it did the day after installation 6 years ago.

Yea, I already knew the answers to my questions before I had the contractors out, it made my decision pretty much on the spot.

 

[schmism]

a hole with no screw or nail on the top of the rib will rarely if ever leak,

I completely disagree. A hole in a rib will leak just the same. My pole barn that is nailed in the ribs has a number of leaks. all from around nails in ribs.

I have never seen an installer predrill a hole to fasten the metal to the roof.

Its my understanding that all manufactures recommend flat attachment staying off the ribs. (least thats been 100% my experience reading the directions for 3 different types of metal ribbed roof ive put down)

from a mechanical standpoint, from a long term durability standpoint in conjunction with thermal expansion and contraction. It really only makes sense to attach it in the flats. (never on ribs)

 

[massey990]

A hole in a rib will leak just the same.

Sorry but you are entirely wrong, and as far as your other observations go they are the exact opposite of my experiences with both manufacturers and roofing contractors.

simple science dictates that on a 5 V panel almost ALL the water will be running down the flat and away from holes at the top of a rib. Gravity has the same effect on water as anything else. To prevent getting flooded build on top of a hill rather than the bottom.

In high winds water can blow up under the laps and thorugh holes in the ribs but it is not very common.

About pre-drilling, to get the most professional looking roof a contractor will always pre-drill the holes so the screws line up almost perfectly.

 

[magicheater]

I agree with those that follow the manufacturer's guidelines, however, a hole with no screw or nail on the top of the rib will rarely if ever leak, a hole in the flat will almost always leak.
Most of the installers I have observed that fasten through the ribs pre-drill the panels.

I tend to agree with this.

I just had a new shop, and horsebarn built. The contractor himself did not show up the day the roof was being put on, until about noon. The self appointed foreman/lumber salesman instructed the workers to pre-drill in the flats. I prefer in the ribs... The rest of the roofing WAS put in the ribs...

I can't help but thinking 10 years down the road, when possibly one of those neoprene washers loses it's seailng properties, that put into the flats will allow a lot more water, to possibly seep in. The closer to the bottom, the more water... On top of the rib, lots less water running by, and most should shed off.

In 1988, my Dad built a carport, and put screws in the ribs. No leaks to this day. I also put a new 36' X 64' horsebarn up myself, in '00, with screws in the ribs, and no leaks either.

I guess maybe a lot has to do with taking your time, and if a rubber on the screw squishes out, is over torqued, etc., take it out, and replace, not just go on to the next...

I can live with my decision to put them in the rib... JMHO....

I have only built metal roofs this way and have had no failures to date. A little more care when fastening the screws but hey, you are not slamming shingles here.

 

[tallyho8]

This is the most important difference between using screws or nails in the flat:

When you nail in the flat the nail bends the metal down around the hole creating a funnel shape that will direct water down the hole if the nail becomes loose.

When you screw down the flat, the screw pulls the metal up around the screw making a dam around the hole and if the screw becomes loose much less water will be diverted into the hole.

If you ever pre-drill holes, make sure that the drill bit is a couple of sizes smaller than the screw so that it will pull the metal up around the hole.

 

[cisco]

I've no clue what the majority of manufacturers specify, but the 26 gauge 5V on my tractor shed came with instructions on screw (NO nail, as they tend to back out over time and innumerable hot/cold changes) density patterns per wind speed resistance. Since I"m on the coast of SC, I selected the 130 mph pattern and followed the instruction diagram - 3/4" plywood screwed to underlying structure (2 X 8 rafters) and then 1 1/4" screws with washers along all edges at top of V and mid-way on intervening flats, and then up the roof line on the V every 9 inches. Sure put in a lot of screws, and at 2 years no leaks. I do NOT want a hurricane to visit, but if one does I'll be interested to learn how the roof fares.

 

[tnmike]

Ive got an old house with lead nails on the rib. Over the years the nails back out leaving the lead not touching the tin. Ive been pulling those nails and replacing them with screws with rubber washers. I have had no problems crushing the rib. No leaks. The screws hold much better, there is no doubt about that.

ALL of the new metal roofing Ive seen put up have the screws on the flat. Eventually it seems to me that the rubber washer would have to deteriorate, shrink, crack and cause leaks. I dont know how long the time period is before this happens but it will happpen. I would no doubt screw the flats if I was putting up a new roof.

 

[BlacknTan]

My roof is screwed down on the flat part. Other guys screw through the rib .. I've seen it done both ways.

 

[magicheater]

So we have a consensus, screws are better than nails. :thumbsup: Just to clarify my comments on fastening through the rib I have attached a few pics to make sure we are all talking about the same thing. Since I have had no failures in the 20 years I have been using this method I will stick to it. I do tend to use a minimum of fasteners when doing a roof as you may notice just to minimize the penetrations but I would fasten on the flat if I was doing siding. Bottom line is that if your roof don't leak you must have done something right, however you fastened it................