How to a Install Metal Roof details laying thin gauge steel roofing for any building. This guide includes images of which side laps and where to put your screws. Pro Barn Plans is specifically tailored for outside building construction, but this method works for houses and commercial buildings as well.
Sheds and barns can have any type roof. They can have plywood decking covered with shingles or you can use batten boards covered with metal. We will focus on the metal type since it is the method of choice for sheds and barns. As we mentioned before, How to Build a Shed or How to Build a Barn do not include any instructions on what to do when you get hurt.
How to Install Metal Roof Preparations
Before you go off half cocked with eagerness to get your building in the dry, you will have to make some preparations and decisions before you proceed with How to Install Metal Roof.
If you need insulation, then you have many options. The most effective is to have insulation blown in the attic once your ceiling is finished. Many types of buildings do not have finished ceilings, so there are other methods. Check with your metal supplier for their recommendations because this varies across the country depending on climate.
Important note: If your metal supplier wants something done differently than we have here, then by all means GO BY THEIR INSTRUCTIONS!
How to Install Metal Roof begins with ordering your metal. Your metal supplier will be able to provide you with a length of metal accurate to within 1/16″. As soon as you know your rafter length, then you should be able to measure the length of metal you need. Be very careful when taking this measurement and be sure to allow for any overhangs or cornice if applicable. Typically the metal can be ordered the same length as the rafter when no cornice at all is involved. This way 1 1/2″ can hang over the bottom batten and down from the center at the top.
- Nail down a batten board flush with the outside edge of the bottom of the rafter tails. 2 x 4’s work best but you can substitute wit 1 x 4’s if you really know what you are doing. They can be any length; just make sure they break on a rafter.
- If you want overhangs, then make sure you hang over “wild” enough so you can saw the battens later. Space them 24″ oc like the rafters. Cut two gauge blocks 20 1/2″. Use them as temporary spacers.
- Position a string in the center of the ridge and run it the length of the building. Be careful to note the distance from the top of the metal to line. It should be close to parallel. If it is not perfect, then be sure to go with side with the shortest measurement for each sheet.
- If you are using 36″ metal then calculate the overall coverage by multiplying the total number of pieces and adding 2″ for the lap one time. For example, if your shed is 10′ long and has 6″ overhangs, then you will need close the 11′ of coverage. When you do the calculation for exact coverage you will come up with 12′ 2″ using 4 sheets.
- This is an extra 18″ hanging over the edges (9″ on each end). You want no more than 1″ – 2″ if you are not using a corner piece. That leaves 7″ – 8″ needing subtraction. To avoid cutting the metal you can try lapping it back an extra rib and see what that does. Don’t forget that width of the overhang is slightly adjustable.
- On the end away from the most visibility, put a mark on the top and bottom batten at the distance for what you came up with in your calculation. Don’t forget the metal needs to hang over the overhang at least 1″.
- Position a piece of metal with the small end on the marks and tack it into position with a screw at the top and bottom next to a rib in the flat next the rib that laps.
- Note the length of the metal. It needs to be so that you have 1′ – 2″ hanging over at the bottom and about the same down from the center at the top.
- Position another piece and tack it down the same way with the small side lapping. Note how the metal lines up at the bottom while maintaining a parallel overhang. Adjustments can be made at this point to reduce the stair stepping. You can move the top in or out and do the opposite for the bottom.
- Once you are satisfied with the fit, mark the battens along the edge the metal. Put marks wherever you can because the outside ones will soon be gone. Remove the metal and get it out of the way.
- From the marks go another 1″ – 2″ in so the metal will hang over. Allow for any fascia boards you may be planning on as well.
- Cut the battens only on the end where you are starting.
- Lay the metal and screw it down as you go. Screw every flat next the side of the rib that laps and in every batten. For 10′ long metal, this translates into about 20 screws. Remember not to screw the top.
- When you get to the last piece. just tack it down so you can repeat the process of sawing the battens.
- Repeat the procedure for the other side except this time you need to make the ribs match up at the top. You don’t ant variations in the overhang when you get to the end.
- Start the ridge capping on the same end you started the metal from. Tack it all down with a screw it each corner. Make any adjustments so long as no empty screw holes get exposed.
- If you opted for corner pieces going up the eaves, then screw them on now. Be certain you hold them square and don’t over tighten the screws. When a screw is properly set for metal, then rubber washer is slightly flattened.