Installing and Squaring

Here we will teach you how to square and install your galvalume metal roof.


Squaring the metal roof: The first sheet.

Center the middle rib of your first metal sheet over the rafter.First let us say that we recommend you using your metal manufacturers detail manual. Follow their process if you want to follow warranty guidelines. There are also different types of metal roof systems. Our metal roof system we describe will be based on 29 gauge 3' corrugated galvalume metal sheeting. You can always add more screws or thicker metal... it's your roof and your money.

When installing your metal roof it will be easiest to have 3 people but 2 can make do.   Get a pouch full of screws and your screw gun of choice and head on up.  Grab the metal from the groundsman, work with each other as you pull the metal up to the peak.  Remember to face the 1/2 inch flap on the metal inwards.  This flap is called a purling leg or purling lip.

Place screws on the right side of the rib. Double screws at edges.Place the center rib of your first metal sheet over the outside rafter.  Once you get the piece centered, check the overhang on either side of the purling run at the eve.  Around 3" is a nice average overhang for a metal roof.  Once centered with the correct overhang go ahead and tack it down.   Place a couple screws in the top, a couple in the bottom just to hold it down.  Don't place any screws on this sheet where your purling overhang the rafter.  You'll need to pull back the metal and trim the purling ends later so don't put any screws there.  Obviously in a windy situation a couple screws wont hurt.  Since we are trimming it later, we'll go ahead and make those marks now.  Use your pencil and mark on the purling next to the metal on every purling run.

Laying the consecutive metal sheets and how to keep em lookin good.

Before you pull up the next piece we are going to mark the metal to identify on this sheet where the purling lay underneath.  This will tell us where the center of the purling is so we know where to step as well as place our screws. If you have an extra man, have them start at the top and mark on the metal the center of the purling. They will work their way down marking on the edge of the metal for the center of each purling run.  While they are marking you can be putting some more screws in.

Once they are at the bottom, they'll grab the next metal sheet and with the ground mans help pull it up into place.  The purling leg should still be facing inwards and should continue to do so until the last sheet of metal.  Once in place, the groundsman should climb the ladder and help corrugate the metal ribs.  Flush the the ends of the metal and check out measurement on the overhang again.  With a square roof and square metal the measurement should stay the same across the length of your pole barn. 

Step next to the metal ribs and use your weight to corrugate the ends correctly.  If the metal sheets do not corrugate it will adjust the angle of the metal sheet and begin to run as if you roof is out of square, when in reality it was you.

You might have to pull the sheet up or down slightly if the roof is actually out of square.  This is called "saw toothing" due to the edge it creates on the overhang.  It cuts like a saw tooth as well so be cautious of them.  You shouldn't really saw tooth more than 1/8 of an inch. 

Finished overhang on the metal roof.If it seems like the falling angle of the roof is throwing the metal out by more than 1/8 of an inch across the metal sheet then you can kick it into place bit by bit, sheet by sheet, saw toothing as you need until the metal sheet lines up correctly again.  To kick it, you would tack the top of the sheet down with one screw.  Move to the tail and kick the sheet over.  The ribbed end will bend a little allowing you to kick the metal sheet 1/8 to 1/4 inch or so. 

You can use the purling like a ladder system.  Agile little buggers can run up the purling with the metal pretty quickly.  I do not suggest standing underneath of the sheet without having good control over the sheet.  If a sheet this size slides and is dropped on someone underneath it, the resulting injury could be lethal.  The metal edges are extremely sharp.  If it is your first time dealing with metal then wear gloves and a long sleeve shirt to help deter minor slices.

The ending sheet.

Continue installing metal sheets tacking them, checking the overhang, adjusting as needed and marking the metal on center of the purling until your last sheet.

Take the last sheet and turn it around so the purling lip is facing inwards.  If your roof is square, then the center of the last sheet should come out over top of the last rafter just like your first metal sheet was placed.  If the roof isn't square, you'll see by just how much by the position of the center rib. Either way, perfect or not, there isn't much you can do to fix it so tack it into place.  Just like the opposite end we will not tack down the metal sheet on the overhanging purling.  Take your pencil and mark on the purling next to the metal on every purling run like we did on the first sheet while you are marking the center of the purling on the metal.

Use this process for the opposite side.  Start from the same end that you did on the first side so everything remains symmetrical even your pole barn or roof is out of square a tiny bit.

Once done tacking the roof into place on both sides you can start screwing off the metal sheets at every purling run. Check your metal manufacturers detail manual for placement of screws for the type of metal that you will be using.  If you are using our system then place a screw to the right side of every rib, and double the screws all around the edges.  Don't screw down the top purling run.  When you place the roof vent the screws will tie down the roof vent and the top of the panel.