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Lean to rafter spacing for metal roof4/11/2024 ![]() The installation of metal roof purlins is critical for the structural integrity of the roof. However, for roofs with heavier snow loads, the spacing should be closer, around 2 inches on-center. Typically, the recommended spacing for metal roof purlins is 3 inches to 4 inches on-center. The spacing of metal roof purlins depends on several factors, including the type of metal roofing, the snow load in your area, and the spacing of the roof framing. In this section, we will discuss the spacing, installation, and distance details of metal roof purlins. Purlins are structural components that support the roof and transfer the weight of the roof to the load-bearing walls or columns of the building. I ended up having to run it down the same direction as the tin, I lapped it 6 to 8", I hope that will work as that all I could think of doing.If you are planning to install a metal roof, it is important to understand the role of metal roof purlins. I got the metal up this week, I tried running the roofing felt across the roof but it didn't work. ![]() Please let me know if you remember the book. I've got 2 framing books and can't find anything on bracing a scissor truss. It's easy to do and only takes about twice the length of 2X4's as the length of your roof. ![]() That is where you really get your strength. Please check out a good framingīook on how to install 2X4 bracing inside the scissor trusses. So, it was much easier to screw each sheet as I wentĪs the purlins would have been missed otherwise.Īlso GW, it's difficult to tell from the photo but, I can't see the diagonal bracing on your trusses. Keeping my purlins as straight or as evenly spaced as you guys. I have to admit your idea about punching is great for you pros but, I have to admit that I didn't worry a whole lot about Yep, Glenn, never let it be said that I let my ignorance overcome good sense!!! After installing the Icyene, the screw was tight in the hole and none have ever leaked. I did miss an occasional purlin on the garage and left the screw in place even thought it was loose. I had no problem with the garage or house with the self tapping metal screws with rubber washers. Again, underneath I sprayed in Icynene with no vents and have no penetrations anywhere on the roof.Īs to pre-drilling the holes for the metal screws, it seems a total waste of time and energy to me. On the house, I went ahead and used 4X8 sheets of OSB and covered it with 30# felt before screwing on the metal. Of course I can see the foam from the garage floor and have never seen any condensation, leaks or insects of any kind. I then had the bottom sprayed with Icyene foam and that's it. On the garage I used 1 X 4 purlins spaced 3' on centers bottom to top. I used metal on both and have had no problems at all. I built a 3 bay garage and put an apartment in one end to live in while building my house. They are color matched to the roofing and are only like $2.50 more per bag than the others. This allows leaves, pine needles and the like to slide over them and off the roof rather than hang on the screw heads. The low profile are less noticable and there is a Torx # 20 fitting in the screw head. If you have trees you might also check into the low profile screws rather than the hexhead. Don't draw them down to where the washer buldges past the outside of the screw or they will split and dry rot and leak. Only draw them down until the washer is tight. Then used a cordless drill with a torque adjustment to put them in. They advertise the screws are self tapping but you will end up with a lot less scratching trying to get them started. When it is all done the whole horizontal row of screws are lined up. You can actually drill 2-3 sheets at a time. Using a drywall square mark the horizontal position of the screws which correspond to the location you want them to appear on the roof(from the bottom edge up) either on the sheeting or midways of the purlin. The metal will expand and contract with the weather and too many will not allow this to occur and end up with a bad looking roof. He stated that when home owners put it on they put way too many screws. The more holes that are put in the roof the more chances for leaks. The main problem is the drip edge end and wind. He has put on several hundred and never had any problems. ![]() The screw placement was every 36" horzontal with the exception of the bottom and top which were placed midway center of the flats. He said there was not a problem with doing it that way. The main reason I used sheeting is that mine is in the woods and wanted to prevent a place for bats, flying squirrels and bees to nest. A friend helped me which is a metal roof installer. GW I used 5/8" sheeting on the roof of the cabin(10/12) and 1X4 (4/12) purlins on the porch.
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