Foreword: This will be a third of the four part series on the installation of metal roofs. In part one of this guide, I’ve described the process of preparing to install a metal roof – safety considerations, how to measure a roof, how to get exact roofing panel sizes, and how to properly install roofing underlayment.
In Part two, I went over the tools and materials needed to properly install a metal roof.
In this part, I will go over the actual installation of the standing seam metal roofing panels, and in the last part of the metal roofing installation series, I will show you how to install an aluminum and steel metal shingles that also last a lifetime, but are not as widely used, because they require special installation techniques that are different from the standing seam roofing installation method.
In this guide, we will not cover several topics of metal roofing installation such as sky-lights flashing on a standing seam roof, as it is a far more advanced topic and requires certain level of experience from the installer in order to be done correctly. In fact, any advanced installation techniques and flashing details involved in a metal roof installation process will later be described in great detail on our online Metal Roofing Store where you will be able to purchase aluminum and steel roof shingles, as well as learn how to install them on your home, all while saving $1000’s.
Introduction to DIY Metal Roofing Installation:
What we will cover in this guide, will be related to the basics of metal roofing installation. As our perspective model, we will assume that the roof we will be installed on a simple gable roof of a ranch style home. Our hypothetical home has one stack pipe and no chimney or skylights. Chimney and skylight flashing will be covered in the later post. For the roof ventilation we will be using gable vents…
Well, lets start installing our metal roof!
Step one – installing drip edge.
Installation of drip edge is usually rather simple. but for a novice roofer it can be a challenge. I’ll take a step back to the first part of this guide – when prepping your deck, make sure that old drip edge is completely removed and all rotten wood (boards or plywood sheeting) is replaced.
There are several opinions as to whether install drip edge under or over the underlayment. In theory if you install drip edge over the roofing underlayment, water may get under it. In reality, metal drip edge gets installed so tightly, that water just rolls over it. Therefore I always install underlayment first, and then go over with the drip edge.
Advantages of installing drip edge after the roofing underlayment has been installed, are as follows: You do not waste any precious time during the installation of the drip edge; when and if your roof is open and it rains, you may not have enough time to cover it, that’s where having water and vapor barrier in place really comes handy. Second reason is the safety. When I install underlayment, first I can trim the edges as I please, in case that a hang off of the roof is too lengthy. If your drip edge is already in place, and underlayment hangs off of it, trimming it may be rather dangerous, while sitting on the edge of the roof. Lastly – it really does not make much difference in terms of performance. The metal roof will keep the water out, and the only water on the underlayment will be condensation. If the rain water gets onto underlayment after the metal roof has been installed, then you have bigger problems to worry about.
Install your drip edge using either screws or nails about 8-12″ On Center (O.C.) in a staggered pattern for optimal rigidity. Overlap individual sections by at least 2″ and don’t forget to open up the lip of the overlapping section for a better fit. Install drip edge along all eaves (horizontal ends of the roof).
If you have a hip roof, trim your drip edge so it overlaps the batting section.
Note: Usually you will receive a drip edge with 1 1/8″ face. You can optionally order 2 1/8″ face or any other size as well as vented drip edge, in case you want to do the soffit / ridge ventilation and you don’t have any soffits.
Depending on your metal roofing supplier, you can order pretty much any type of a trim detail custom made to your specifications. Unless you specify, you will usually get the standard trim that your supplier has. I once got a 2″ face drip edge while I was expecting a 1″ and 2 inches did not work, so I had to exchange them. Think about such things ahead of time, and you won’t be wasting your time and money – always specify what you want to get. Most fabricators / suppliers will accept your drawings, even hand-drawn on, a piece of paper.
Step two – Gable / Rake trim:
In standing seam metal roofing there are at least two ways to trim the gables of your roof with many variations. Two basic once include either using a special gable trim or a regular drip edge. I prefer using special trim as it is easier and safer to install.
Installing your gable trim may have to be done either in the beginning or in the end of the roof installations. This will depend on how you plan to layout your roofing panels If you start with a full or partial panel at the gable, than you can put up the gable trim as soon as your first (and last) panel is installed. You will need to bend up 1-1 1/4″ lip on the outside edge of your panel. This will serve as a hook for the gable trim. Optionally you can cut out the outside part of the double lock on the panel itself, if you are using a full panel. If you will be bending the lip, you can ether use the hand seamer / folder or a special roller (which costs about $500, and you may not want it, if you are only doing one roof). If you use the hand seamer / folder, your bend will not be perfectly straight, but do not worry about it as the gable trim will hide the imperfections. This will be a very tedious process, especially on a longer panel.
If this will be your last panel, measure the distance between the edge of the roof and the edge of the last full panel – this will be the pan width of your last panel. Add at least an inch to this width for your fake lock. Make sure that you measure both top and bottom of the panel as this width tends to be slightly off due to framing being out of square and panel creeping. You don’t want your panel to bump out by an inch or two.
Once you have prepared your first and / or last panel, and created the fake lock to hook your gable trim to, line the panel up so it is flash with the rake board. If this is your last panel, and you measured everything right, the panel will be flash with the rake board or you may have it bumping in or out by 1/8 – 1/4″ – this is normal, and will not be noticeable.
Hook your gable trim into the fake lock, pull it down with your fingers and drive in the color matching hex screws with rubber gaskets, approximately 12″ oc to secure it. In some situations, mostly for aesthetic reasons, I measured 2″ from each end and measured the remaining distance for equal spacing of screws (which usually came out to about 10″ oc).
In some situations you will be required, or may choose to use a drip edge as gable trim. In that case, instead of bending up 1 inch of fake lock, bend down about 7/8″ lock to a 90 degree angle. Hook that side lock to the drip edge and fold in down with your fingers. Use hand seamer to tightly crimp the lock.
All other trim, besides the drip edge and on some occasions gable trim, will be installed as you get to it with your panels.
Step 3 – Installing your first panel, and the field panels.
Whether you are using gable trim or drip edge for your rakes, the first panel will be the most important, because it will determine if your roof is squared, if any penetrations line up in the center of a metal pan or on a rib / lock. You definitely want to avoid having any penetrations lining up with the lock, becuase it would be quite challenging and problematic for a first-time installer to flash it properly. This should be solved ahead of time by making sure that your first panel has an appropriate width, so that you end up with a panel layout where you have all the penetrations through the center of a panel.
Assuming your have the correct width of the first panel, and that all the drip edges are installed, you will have to create the hook-lock at the bottom of each panel. This hook / lock should be 7/8 of an inch wide and folded down (see photo below). Also notice the little “ear” sticking off on the side of the double lock. You will need to make this to wrap it around and crimp, once the panel is installed.
Hook the first panel into the drip edge, align it flush with the rake board and install 1 screw through the pan, all the way at the top of the panel (about 1 inch from the upper edge of the panel). This screw will hot it in place while you are installing clips.
Space your clips 10-12″ OC, and using special flat-head screws, attach the panel to the roof deck. To avoid dents in the panel, install screws into outside hole of the clips. If you are located in high wind area you may want to put two screws into each clip, but I would actually increase the number of clips to 6-8″ on center instead of using two screws. Never put two screws if you have boards instead of plywood. Two crews will split the board, which will cause the panel attachment not to be secure.
Once the first panel is installed, snap on the next panel. I found that the easiest way to do this is to hooks the loose panel into the drip edge and insert the tip of single snap lock into the double snap lock, then push the panel all the way up, and only then start putting the lock together. See video bellow:
Use a rubber mallet or the rubber handle of your hammer to snap the seams of the roof panels. Using your palms will begin to hurt after just a couple of panels. Make sure that whatever you use is soft as to not dent the metal panels.
Repeat the process until all panels are installed. Measure and install your last panel as described above. Repeat the process on the other side of the house.
Step 3.1 – flashing a vent (stink) pipe.
If you have a vent pipe (most likely you do), you should have ordered an appropriate sized pipe boot with a metal/rubber flexible adjustable bottom, designed for corrugated sheet and standing seam metal roofs. I hope you aligned your panels so that the stink pipe lands between the ribs. As you approach the stink pipe in your installation of the panels, getting as close as possible with last full panel that does not require cutting, finish installing it, and then measure the distance from the bottom to the center of the pipe, and from the side where the last panel is. Locate the spot where you will be cutting in a hole in the panel for the pipe, and make sure to cut the hole which would be 1/2 – 3/4″ wider than the pipe.
As you can see in the picture above, we actually had the rib sitting 1″ away from the pipe. We could not avoid this and had to deal with it, but for you, I strongly recommend to spend 5 extra minutes measuring and not doing it the hard way.
Once you cut your hole in the panel, put it up, install the clips, and now you should be ready to install the pipe flashing. Put your pipe flashing on, align it with the panel, use pencil to mark the location of the flashing and pull it off. Apply a thick bead of Solar Seal 900 or an equal exterior grade sealant / caulking within the perimeter of the flashing. Then, set the flashing back in place so that its base is completely sealed by the caulking. Finally, fasten the flashing down with the hex head rubber gasket screws, spacing them about 1.5-2″ apart.
Once again, in order to avoid the situations where roof penetration lands in the center of the lock, measure carefully beforehand!
Step 4 -Installing z-bars and ridge cap.
If you are using the ridge/soffit vent systems, make sure you are not installing it on a low slope roof, as water may get inside through the perforated z-closure.
Cut your z-bare to the width of one panel. Make sure it fits tightly, but not too tight as to scratch the locks of the panel. Usually go about a 1/4 less than nominal width of the panel. This gives you enough room for a snap lock of the next panel to fit in, and it will help you to end up with the minimum gaps between the edges of.
Cut a small piece of ridge cap (about 2″ wide), align in so that it is in the center of the ridge, laying perpendicular with the locks. Mark the outer edges on the top of each rib. You will align your z-bars and the ridge cap to these marks.
Use the first piece as a template, and cut enough z-bars to accommodate every panel on your roof (both sides). Using double-sided peel-n-stick foam or some type of exterior grade caulking such as Butyl, Urethane, or similar sealant, caulk the connection area between the panel and the z-bar. Attach z-bar with 3 screws, and caulk the side gaps so that a wind driven water would not be able to get in. As for the caulking type of choice, we always use a clear (or color matching) Solar Seal 900. It works awesome!
Once all of your z-bars are up and sealed, take a section of the ridge cap, and cut a 2-inch line down the center bend, on the end of the cap. At the same end, cut off 2 inches of the lock and bend down the two flaps. This will be your end-piece. Align the flaps you’ve just created with the gable trim and hook in one side of the ridge cap into the z-bar. If your z-bar is spaced too widely or narrowly, you can bend it in or out so that it fits your ridge cap. Hook the second (unclosed) lock into the opposite z-bars all along the length of the cap. Once it is completely clipped in, use your hands to close the opened lock (lip) on one side of the cap, and then using the hand seamer crimp both sides of the cap.
Take the next section of the ridge cap, and cut of about 3″ of locks at one end of the cap. Do not cut along the center. Apply two lines of caulking where the connection between two pieces will be made ad install second piece the same way you did with the first, using the end where you cut off 3 inches of lock, to overlap the 1st piece. Do not use any screws. The connection should be watertight and will not leak.
Once all your ridge cap is in place, your roof is pretty much complete. If you have the stack or bathroom vent pipes, I will show you how to flash them the right way in the next post. In the mean time, if you live in the snow country, you may want to have the snow guards installed. Visit Berger snow guards, to find the style you like, and locate the supplier to buy it.
Hope you enjoyed reading this post, and that you found the information helpful. As a word of precaution, always remember to safety-in using a proper fall arrest equipment and anchoring methods. Never ever work alone. Check back soon for the last part of the series on the Installation of Metal Shingles Roofing system.
P.S The photographs in this article were taken during the installation of a standing seam metal roofing system in Wayland, Massachusetts, which was completed in June 2009.