metal roof guestion

[williet]

Hi all,
I've been told that if you put the screws into the ridges of a metal roof, the are less likely to leak and last much longer. The manufacturers recommend they go into the flats.....Which is better?

[glenn kangiser]

That is only for nails with seals on the old wavy corrugated galvanized type of roofs.

Flats with neoprene seals squashed only to the edge of their washer - not beyond for the new stuff with high ribs.  Stitch screws are commonly put into the high ribs sheet to sheet only to keep the edges together on the same row lines that the sheet to frame screws go.

[williet]

Thanks Glenn,

That's what I thought too. The roofer who's doing my brother's house said he always used screws and centered the rib with them..... something about the high point not being exposed to as much water?? I thought it was silly.

Just wondered if any here might have actual experience with it.

[glenn kangiser]

I have built about 300 steel buildings using the newer high rib and am familiar with the old corrugated methods here.  Before self drillers they used to use wires with a lead button on the end to wrap around an angle Iron purlin.  It simply went through a drilled hole on the high point of the wave and was pulled tight and bent around the angle iron leg sticking down.  this created a bit of spring tension on the lead seal and along with it being the high rib, would prevent leaks.  Surprisingly they seldom dripped.  I still nail corrugated with a palm nailer on top of the high ribs with neoprene seal nails and allow the rib to spring down a little.

As in here -

A self driller on a high rib of new style sheeting would be very hard to keep from putting an nasty dimple in the rib unless you very carefully set each one or had one of the expensive depth sensing screw setters and even then they were lots of trouble.  A clutch drill may do it but there would not be much tension on the screw and it would likely work loose over time.  Set in the flat tight against the sheet and purlin, it is not likely to ever come loose.  I have buildings that are 32 years since I built them and have never had a customer complaint with loose screws -- thousands upon thousands of screws.

[Redoverfarm]

Willet another little tip is to pre drill your holes.  Yes they are suppose to be self drilling but usually don't penetrate. Probbaly would without paint .  I usually evenly measure up from the bottom and with the use of a T-square(drywall).  If using perlins just measure up where ever your perlins are to hit center. If the roof has several pieces of the same length I drill maybe 4-5 at a time. Makes a nice looking job with all the screws lined up.  It also prevents scratches from missed hits and a small impact does the trick.

[williet]

Thanks guys,
it will be awhile before I do mine, but my brother's will be done in a week or so...as soon as the metal gets here. The roofer says he's going to use screws on the ribs. I wouldn'tb but it'snot my house. I also asked about perlins, lathing strips, and he said there was no need as the roof is decked with osb. Would it not be better to place lathing strips over the tar paper to allow for sweating and offer some airflow?

[glenn kangiser]

The ribs should vent pretty well.

[MountainDon]

That's the same thing the roofer that did our metal said

[williet]

That's the same thing the roofer that did our metal said

Which????It needs lathing or the ribs will do the job?

[glenn kangiser]

The ribs will do the job.

[MountainDon]

Thanks Glenn. Yes. The ribs do the job.