Tiny Roofing Epiphanies

Roof Complete!

Finished Roof

Now that my roof is on (and appears to be water tight), I thought I would share the roofing wisdom I accumulated along the way.

Purchasing Roofing Materials:

  • First of all, you can do this. Many people are too intimidated by metal roofing to attempt it themselves. However, most of those same people end up wishing they had done it themselves once they hire somebody else do it and see how easy it is. If you have built a floor, framed your house and put up rafters, you can put on metal roofing. It’s really just a matter of hauling the sheets up to the roof and screwing them down.
  • Don’t feel like you have to use the same roofing panels as Tumbleweed. The Tumbleweed plans specify a MaxRib product that is nearly impossible to get in California. I strongly suggest taking a trip to visit two or three of your local roofing supply companies to see which one is best able to help you figure out what you need and get it ordered. Then, use whatever product they recommend the comes in the colors and/or contours that you like. If you let the roofing supply company help you, they will be able to order panels that are exactly the right length so you won’t have to cut them all (which I rapidly learned is kind of a pain). In the San Jose, California area, I recommend a visit to ALL Roofing Materials.
  • You don’t have to use metal roofing panels at all. You could go with something like the cool Onduvilla product like Jenna did here.
  • When ordering your materials, don’t fail to consider ventilation, something Tumbleweed fails to properly address in their plans but which could result in a serious mold problem if you ignore it (just ask Ella). If you have provided ventilation holes at your eaves, you need to continue that ventilation path all the way up the inside of your roof, through the peak of your roof and back out through your metal ridge cap. If you use the standard outside closures that generally go between the ridge cap and the roofing panels near the peak of the roof, you will essentially seal off the area underneath your ridge cap, terminating your ventilation path. Instead, you might consider using one of a number of different products that can be sandwiched between the ridge cap and the roofing panels allowing ventilation while also preventing bugs and critters from getting underneath your ridge cap. I decided to use VersaVent, a breathable foam material sold by Metal Sales ($25 for a 10 foot roll). Another option would be a COR-A-VENT v600 product.
Ventilation Holes Complete

Ventilation Holes in Peak

Versa-Vent Applied to Underside of Ridge Cap

Versa-Vent Applied to Underside of Ridge Cap

  • To order your panels, you’re going to have to know how long they need to be. First, measure the length of your roof sheathing from the peak to the eaves. Add to that the amount of overhang that you want.The exact amount of overhang is up to you, but should be between 1-2 inches. I thought 1 1/2 inches looked good on my house. Finally, subtract the amount of space you need at the peak so that the panels do not overlap whatever venting you have planned up there. For example, if you have a 12/12 roof (45° angle), your ridge beam is 1.5 inches wide and you drilled 1 inch holes along both sides of the ridge beam for ventilation, then your roofing panels should end at least 2.5 inches from the peak [(1.5 / 2 + 1) / cos(45)]. Be sure that whatever ridge cap you order is long enough to cover the gap between the peak and the top of the panels plus at least a few inches.
  • I recommend ordering at least one extra panel for each side of your house. If you have never done this before, you’re likely to make a mistake cutting up at least one of the panels (like I did cutting the panel that went around the skylight) and you will want a way to recover quickly without having to order more. You might also want some extra panels to use on optional additions like a porch roof or a propane/battery storage box at the front of the trailer.
  • When choosing a style and manufacture for your metal roofing, pay attention to the dimensions of your gable and eaves flashing. At over 6 inches wide, the flashing I received had such a large profile that it completely covered my beautiful stained cedar fascia boards. I ended up having to re-bend all of my flashing into a smaller profile that looked reasonable in proportion to my tiny house.
Gable Trim Before (Way Too Big for my Tiny House)

Gable Trim Before (Way Too Big for my Tiny House)

Gable Trim After Re-bending

Gable Trim After Re-bending

  • When you order or pick up your panels, be sure to also order or buy a quart of matching paint to fix the scratches you will inevitably get on the panel surfaces.

Preparation:

  • If the plywood sheathing on your roof was attached in such a way that there are horizontal seams between the plywood, you might consider adding some caulk to those seams. If water somehow gets underneath both the metal roofing and the tarpaper or Tivek, it will collect in any horizontal seam until it soaks through the underlying studs and drips into the house (I learned this the hard way during a heavy rainstorm that occurred between when I put my tarpaper up and when I put my metal roofing on).
Caulk in the Horizontal Roof Sheathing Seams

Caulk in the Horizontal Roof Sheathing Seams

  • Before you put your first panel up, I recommend measuring out your entire roof and marking where each rib or at least each overlap of each panel will go. This will help you to figure out how the roofing will layout relative to the skylight and to the edges of the house. The skylight has slots for the siding to slide under on each side, but the slots will only work properly with a flat section of the panel, not a raised section. Similarly, the gable trim pieces also need to be screwed down on a flat section of the panel. You may need to shift the entire layout left and right in order to make sure the raised ridges in the panel fall in the right spots relative to the skylight slots and inside edge of the gable trim.
  • Note that the panels do not need to come all the way to the gable edges of the roof. It is okay to allow a 1-2 inch gap between the end of the panels and the side of the roof sheathing, provided the gable trim will cover this gap. Also note that you don’t want the panels to overlap the side of the roof. It’s kind of like The Price is Right. Get as close to the edge of the roof as you can without going over.
  • I recommend pre-drilling the holes for all of the fasteners while the panels are in a stack on the ground. You may want to drill and install one panel first just to make sure you got it right. One thing I found helpful was to take an 8 foot furring strip and drill holes with the appropriate vertical screw spacing. Then, I could clamp that furring strip to the siding next to each ridge and use it as a template to drill the holes. This ensured that the holes were drilled at exactly the same distances across each ridge and across every panel. Also – be sure to drill your left and right panels separately as the pattern will most likely be different.
Using Furring Strip with Holes as a Template

Using Furring Strip with Holes as a Template

All Holes Drilled in Stack

All Holes Drilled in Stack

  • Although I recommend pre-drilling all of the holes in your panels while they are on the ground, I don’t recommend doing this for the ridge cap because if you mis-measure and the holes don’t end up falling exactly on top of the panel ridges, you have kind of ruined your ridge cap. If your screws are like mine, they should be self tapping which means you can drill them into place exactly where they need to be without drilling holes first. This is both easier and more accurate. I do recommend using a center punch to mark where each screw should go just before installation so they don’t move while you’re screwing them into place.

Cutting Panels

  • I suggest making all cuts over a large tarp so that the tarp catches all of the metal fragments that will be generated.  At the end of the day, you can simply pick up the tarp and dump all the metal shards into the waste bin. This tip is extremely important if your metal cutting workshop is also your bicycle storage area.
  • Horizontal cuts that go across the ridges in the panel are difficult. There’s no way around it. You really have only two options. The first is to just work your way through with a good pair of metal shears. It will take you a while and you will struggle, grunt and probably curse, but you can do it. The other thing you can do is put a metal cutting disc on the end of a rotary tool and use this to cut through the panel. It will make a noise like a screaming banshee and send sparks everywhere, so be prepared and be sure to wear eye protection and to cover all of your skin so you don’t get burned by the sparks. If this sounds kind of scary, then just use shears. It’s a tiny house so you won’t have that many cuts to make, right?
Andrew Cutting Panels

Andrew Making Horizontal Cuts

  • If you have to make a long vertical cut, then I recommend the scoring and folding method. Set up a sheet of plywood on a table or a pair of sawhorses. Put your panel on top of the plywood and line up the cut you want to make with the edge of the plywood. Clamp a 2 x 4 or other long, straight piece of wood over the top of the panel, again lined up with the cut you want to make. Using the 2 x 4 as a guide, score the panel a couple of times along the cut line with a sharp razor blade. Now, begin at one end of the panel and start folding the hanging edge of the panel up-and-down as far as you can go in each direction. You should hear some snapping and popping sounds as the panel starts to break along the line you scored. Continue to work your way down the panel, folding it up and down until the whole panel breaks along that line.
Clamp Panel Along Cut Line

Clamp Panel Along Cut Line

Score with Razor Blade

Score with Razor Blade

Bend Up and Down

Bend Up and Down

Keep Bending Until Panel Breaks

Keep Bending Until Panel Breaks

  • After you have cut your panels, be very careful about stacking them on top of each other and be especially careful about sliding them relative to each other . Any cut surface will very quickly scratch and remove the paint from any other panel surface it touches.
  • Whenever you need to cut the panels, be sure to wear cut resistant gloves and eye protection. I cannot stress enough just how extremely sharp the cut edges of a metal roofing panel are. If you even brush against them lightly, you will get cut. Always wear gloves every time you work with or move the metal panels.

Accessing Your Roof

  • Although you will definitely want one or maybe three ladders while installing your roof, I strongly recommend using scaffolding as well. Ask your construction friends if they have a scaffold you can borrow, rent one for the day or even consider buying a used one that you can sell again later. It is much easier to be able to walk around on a platform at the right level than it is to balance on a ladder. I can’t imagine trying to do the things I did on my roof while balancing on a ladder.
Scaffold

Scaffold

  • Get comfortable crawling around on the roof of your house. I don’t think there’s any other reasonable way to put the screws in the top of your panels or to install your ridge cap. When you go on your roof, I recommend wearing sneakers and making sure that you don’t have anything sharp or metal hanging off your clothes or shoes that might scratch the metal panels. I was tall enough that I was able to reach the peak of my roof from my scaffolding and just pull myself up. Shorter people may need to put a long ladder up to the peak and then crawl onto the ridge from there.
The Better Way To Drill Holes in Your Roof

Working On The Ridge

Installation

  • The manufacturer of your roofing panels should provide installation instructions. These instructions should specify screw patterns along the edges and in the field. However, they may or may not specify how far apart to space the screws vertically in the field. The exact distances varies a bit based on the code in various areas. However, it seemed like the minimum required spacing was 24 inches which is what I used.
  • While using the impact driver to screw down the panels with one hand, put pressure on the panel with your other hand to hold it firm against the roof. This will keep the screw from drawing the panel up while the screw goes in. If the panel gets drawn up, it’s likely that the rubber gasket around the screw will be over compressed when the screw finally goes in.
  • If you do end up over-compressing a screw gasket, it’s probably better to just take it out, throw it away and replace it with a fresh screw. Once the gaskets have been compressed, they seem to lose some of their structural integrity.
  • My roofing instructions called for a strip of butyl tape on both sides of the inside closures at the bottom edge of the panel (just above the eaves). This stuff is sticky on both sides and can be hard to work with. I found it was best to install both strips of tape and the closures in the following order.
    1. First, install a strip of tape along the bottom edge of the roof where you’re inside from closure will go. Be sure to measure the distance between the tape and the edge of the roof such that will fall right under the bottom most holes in your panel. In the end, you want your screws to go through the panel, the foam closures and both strips of butyl tape.
    2. Stick an inside foam closure to the top of the tape you just applied.

      Butyl Tape & Inside Foam Closure

      Butyl Tape & Inside Foam Closure

    3. Before installing the panel, apply the second strip of butyl tape to the underside of the panel, in line with and covering the screw holes you pre-drilled at the bottom of the panel. You can also try to apply the butyl tape to the top of the inside closure that has already been installed. However, I found that the tape sticks better to the panel then to the foam so when you try to install the panel, you might end up brushing the foam and pulling the tape off. I think it’s better to apply the tape to the panel. When putting the panel in place, try to hold the bottom edge up a little bit so that the strip of butyl tape at the bottom doesn’t stick to anything else and get pulled off before you’re ready to screw the panel down.

      Butyl Tape on Underside of Panel

      Butyl Tape on Underside of Panel

  • To attach the panels together at the overlapping ridge, you will need to drive stitch screws through both panels. You can handle this one of two ways:
    1. The way I did it was to drill holes through both panels and then put a stitch screw through the hole. When the panels wereon the ground, I drilled holes in the ridge of the panel that would go on top but not the ridge of the one on that would go on the bottom. After both panels were installed on the roof, I then used the holes in the top panel as guides to drill the holes in the bottom panel. I also placed a small block of wood between the drill and the panels to make sure that I couldn’t drill too far down and put a hole in my roof sheathing as well.

      Drilling Holes in Ridges

      Drilling Holes in Ridges

    2. If your stitch screws are self-tapping, you could also install them in place without drilling holes. Just mark the spot with a center punch first. I would have installed mine this way except that I did not learn this trick until I was installing the ridge cap and the panels were already on.
  • When installing your gable trim, you will need to lay down the strip of butyl tape along the edge of the trim, right underneath where you will screw the trim to the roof panels. Be sure to position this tape at least 1/8 of an inch in from the edge of the trim. Otherwise, when you screw down the trim, it will compress the tape and the tape will squish out from underneath the seam which will not look terribly good. If some of the tape does end up squishing out from underneath the seam anyway, just use some paint to make it match the rest of the roof.
  • There will be several cases during installation where you will have to drive a screw through a strip of butyl tape. I found out the hard way that if the screws do not drive into the hole immediately, the threads tend to grab the butyl tape and spin it up into a big ball underneath your panels. This is not only frustrating and annoying, but also compromises the integrity of your tape. A good way to prevent this from happening is to use a center punch to punch a hole in both the butyl tape and the panel below the tape before trying to install the screw. This will ensure that the screw drives in immediately without snagging the butyl tape in the process.
Butyl Ball

Butyl Ball

Using Center Punch to Punch Hole in Butyl Tape and Siding

Using Center Punch to Punch Hole in Butyl Tape and Siding

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7 Responses to Tiny Roofing Epiphanies

  1. We’re trying to decide on roofing, tpo, the onduvilla or what you’ve done. Why did you decide on the metal option?

    • I really liked the onduvilla roofing. Unfortunately, I had a lot of trouble getting anybody at the company to respond to me. I waited several weeks and finally just had to make a decision (they did finally respond and even sent me a box of samples, but it was too late). Also, the places we found that sold the onduvilla sold it in quantities that were much too large for a tiny house. Now that I have the metal roofing on my house, I’m perfectly happy with it. However, the onduvilla still looks like a great product if you can buy the quantity you need.

  2. Mike says:

    Very cool – I’m having the same issue with my gable flashing. Did you cut it using the straightedge and bend method you use above? How did you re-bend the drip edge portion on the overhang?

  3. Mike says:

    Hi – I have the issue issue with the size of the metal trim i got. How did you cut and bend it smaller to get nice straight lines like that?

    • Hi Mike. Yes, I cut my flashing to size by scoring it with a razor blade and then clamping it down and bending a back-and-forth. As for bending it, I actually took it to a metal shop for help with that . That ended up being a rather expensive solution (about $200). Since then, I have had reasonable luck bending metal roofing on my own by clamping a long, straight board on top of my piece of metal right at the edge of a stiff, straight edged table and then slowly working my way up and down the piece, bending it a little at a time in the direction I want it to go. The longer the piece is, the more difficult and time-consuming this method becomes. But that is also the way the guys at the metal shop did it for me, so I think it’s the way to go. The guys at the metal shop used a metal bar and a metal table which is the best. If you look online, you can also find plans for building your own metal brake which would probably be an even better method. Good Luck. It’s not an easy problem to solve. However, with some work and patience, you should be able to get it done.

      • Thinking about some more, I recommend taking the time to build your own metal brake. I didn’t do it because it looked too complicated, but I think I would have saved myself time and money in the long run.

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