Screwing metal roofing on flat or rib

Which one is correct!

[terrancefitzgerald]

Screwing on the rib adds back tension to the rubber screw seal. However, if attaching to furring strips, most screw on the flat for strength of attachment.

My rule of thumb is, if you’re installing on solid decking, typically new construction or a complete roof rebuild, screw on the ridge. If you’re installing metal roofing on furring strips over an old roof, screw on the flat to get deeper penetration & additional rigidity of install on the roof.

I could be wrong.

[gregdawson]

I like it on the flat for walking on the roof, the screw gives your shoe something to bite on, keep you from slipping as easily

[davedragone]

You are absolutely right about the roof rake catching the screws if they are on the rib…..disaster!!

[JeffsK]

I was taught to put it on the Rib, so water Runs down sides of Rib, if on the Flat it can have Tons water washing down the flat surface towards it and more chance to leak. Also screws on the flat can be blocked by a stick and cause leaves to build up, but if it stops on a ridge its higher and leaves will Slide under it. (no snow here in Florida)

[howardsinclair]

I can tell you some screws or nails will back out over time. The longer the panel is, the more the movement (problem ). So when there is a loose screw on the peak it still sends the water down to the flat. When the loose screw is in the flat, water runs into the structure! Expansion and contraction will cause a screw hole to elongate over time no matter how tight the screw is. The roof is pretty with the screws in the flat, and it's quick to install. . But the roof with screws in the peak will not leak for 50 years, even tho many screws will be loose. THERE IS A RIGHT WAY TO SCREW DOWN A ROOF.

[toddwatson]

Installing steel roof over my deck this weekend, I will be going on the flat. Thanks for the knowledge Ken !!!

[kentperry]

Screws in the rib will move back and forth and eventually work lose or come out. In the flat the screw doesn’t move and the panel will enlarge the screw hole but the screw still covers and won’t leak.

[sagarkk]

In tropical weather countries, it is preferable to install on RIB as the water will eventually flow from flat, and in snowfall region its prefer to install on FLAT, so that we can easily remove the snow.

[sethvlieger]

I put a steel roof on my house 4 years ago I put the screws in the flat and haven’t had a bit of trouble.

[JohnAdams-xcyk]

I worked for a medal building contractor we used R Panel you receive a written warranty from them they will replace the panel if there is a problem but you must place the screws at their requirement, in the flat, and lap screws at the joints of each sheet

[ClassicRur]

great vid. ive found the older guys are adament on the rib but i worked for a company that needed to do it faster so we just went on the flat. theres definetely no wrong way just pros and cons to both methods

[brucethomas]

I was always taught on the rib. Water runs downhill and in the lowest part of the tin..every screw potentially becomes a leak. On the rib is the highest point..water runs off down to the flat part of tin and downhill. Less chance of leakage on the rib.

[jimmydean]

every roof i have repaired has been fastened on the flat. If you tighten down the screws properly they seal perfect on the rib and last longer for many reasons. 1 the rib is the strongest part of the sheet. 2. the rib has flex so as the metal expands and retracts roofs fastened through the rib can move more without pushing out the fasteners. 3. the rib is the high point so even if the seal is not perfect there is less chance of the roof leaking. I did experiments on my out buildings... one side flats one side ribs... I even put the rib fastened panels on the side that gets the most sun. 13 years later some of the flats started leaking and working themselves out... 16 years later I had to replace all the flat screws.... not one leak from the rib fastened side....fasten on the flats if you love doing repair work....

[jonnykerr]

It’s crazy that 90% of the people in comments say rib. I started as a residential and commercial roofer for my Dad when I was 15. Now it’s my company. I do at least 100-120 roofs a year and you need to go on the FLAT.
Modern screws are meant for the flat. They won’t tighten and grip and be leak proof on the rib. They’ll work themselves loose and won’t even seal properly on day 1, let alone day 2, 000… Screw on the flat folks. That’s what every professional I know does.

[ArtisanTony]

I have been doing it for a long time and have done it both ways and never had a leak either way. The problem with the flat is when you try to screw the laps on the flat sometimes the sheet appears to not lay down good. The laps seem to fit better when you go through the rib so i have actually done it both ways on the same job before. In the field I screwed on the flat and at the lap, on the ribs. I know, I just created a black hole. Again, never had a leak on any of my jobs. Even if i did I would not know it because I use synthetic felt under it which sheds the water all the way to the gutter. :)

[justryan]

haha ribs in my opinion, holds the seems tighter. Plus if they work loose water is always going to flow off the ribs to the flats...

[dougs]

I think this stems back from the early days of tin as it was continuously corrugated and the rib was the obvious choice as the lower portion of the rib wouldn't allow the nail (no screws in the old days lol) hole w the lead swatch to seal properly. I believe with today's technology both places are acceptable as long as the surface is flat

[RossWilliamsDC]

When I started in the late '70's in Key West, FL many of the roofs were, and still are, 5-V or what we called V-crimp and we all put the nails, no screws, on the ribs. Also, the washers were made of lead.

[thousandroses]

I know of 2 flat screwed roofs that need to have all their screws replaced because the washers have dried out and small leaks have begun. One of these roofs had the premium cap that covers and supposedly protects the rubber from drying out. These roofs are about 15 years old. What is a bigger problem than replacing the screws is that the small leaks caused rotting in the runners and the same hole can't be used for fastening or worse yet the panel need to be removed and the runner board replaced with fresh if the leak was particularly bad. As a preventative measure, I'd replace screws every 10 years if screwed in the flats. If I'm doing exposed fastener from here on out I'm screwing into the ridges where the water doesn't flow. I think some manufactures recommend screwing into the flats because its more forgiving to a careless screwer and near useless warranty doesn't cover dried out washers.

[bahopik]

My boss's shop screwed in the rib and roof leaks when it rains or snows melts. Like you said panels move do heat, so when it is screwed in the rib the same movement would have more leaverage loosening screw, and rubber gasket would have more area to seal on the flat. In pole barn application I would think screws would grab better on flat part, providing a little resistance to wind rocking the building