Notice: Undefined offset: 1 in /usr/local/src/wordpress/wp-content/themes/montezuma/includes/parse_php.php on line 79

Re-Roofing With Torch-Down Modified Bitumen

Putting on a new roof is way out of my normal line, but I decided to learn it because I love to learn, and eh, because I wanted to save $4,000.   And anyway, I need the exercise.   I will explain this without shyness of my mistakes and in unvarnished words, so you can learn from my good and bad and do it right yourself the first time.

I own a property in unincorporated Everett, WA with a half-acre of developable land, and a house that was built in 1964.   The roof on the house is the original, and is thus in terrible condition after 50 years;   the tenants recently complained about a leak, so as a temporary measure I covered the area with a tarp.
(Click to enlarge… if you dare)
4. 21 Aug 2016

I did some research and found that the roof has a pitch of 2:12, in other words for every 12″ of run it rises 2″.   soffit WThis is easy to measure;   just get under the eave at the gable-end, measure 12″ horizontally from the soffit and mark it, then measure the distance up to the soffit from there.   I found that for rooves with a pitch of 3:12 or less you should not use shingles of any kind, as they won’t shed rain fast enough.   It turns out though that there are several options for low-pitched roofs:

  • Torch-down   —   A sheet of ‘modified bitumen’ (special mix of rubber and asphalt) with rock granules on the surface for long wear against the Sun.   Applied by using a large propane torch to heat the membrane to melting, then rolling out.   $55-65 per square (100 sqft).
  • PVC membrane   —   Sheeting of PVC (PolyVinyl Chloride) where seams are welded with a heat gun.   It is very long-lasting, but must not be installed over asphalt or other solvent-type substrates or the plasticizers will leach out and the roof becomes brittle and shrinks!   One case I saw actually pulled down the brick parapet walls.   Well I’d be laying this right on the shingles, so that’s a no-go, especially at   ~$87/square.
  • TPO membrane   —   a platicized membrane (Thermoplastic PolyOlefin) which is sealed with a heat gun.   Thin and delicate, and won’t do over abrasive shingles.   Also fussy at jacks.   ~$47/square.
  • EPDM   —   a form of rubber sheeting (Ethylene Propylene Diene Monomer) which is sealed with two types of contact cement.   Also too delicate for my application.   These guys are experts.   ~$50/square.
  • SketchSo it’s down to the hairy torch-down, which has a reputation for setting houses afire.   At least I know about that in advance.   Next I did measurements.   I didn’t bother committing this to SketchUp as this was simple, although scrawling on asphalt shingles was messy.   I called every roofing supply in the area, with these results:

    • Stoneway      $72/roll (100sqft)      has epdm
    • American Building & Roofing      $74
    • ABC Supply      $70      archit shingle $73
    • WA Cedar & Supply      $68
    • Seattle Cedar Suppl (Certainteed)      $66.5

    Also I went through Craigslist and found one supplier in (what’s-that-smell) Tacoma with white torch-down for $55.   Well I don’t want white where it will show, but I took his price to Seattle Cedar and got them to part with three rolls of gray for $55;   I had to buy the rest for $65 each though.   $40 for shipping was worth it because their truck has a sky-crane which lifts the materials right up on the roof.   I tried carrying two (108 pound) rolls up the ladder, and that was not very funny.

    Meanwhile I had to learn how to do this torch-down, and let me tell you, YouTube beats all Hell out of Sweet’s Catalogs for learning these days.   This is the best and clearest application I could find:

    Notice the distance away he keeps his torch, the pace of his sweep and unroll, where he aims the torch, and how much yellow flame he has at the roof.   That amount of flame is key, because no flame means he hasn’t evaporated off the ultra-thin polyethylene anti-stick sheet, and too much flame means he’s melted halfway through the bitumen to the fiberglass reinforcing layer.   And notice his seams, where just a little melt comes out, enough to show a good seal yet not too much meaning loss or boiling of bitumen.   He’s preheated the cold end where the hot end torches over.   You’re supposed to pre-heat that cold end so the granules spall or start to sink in, or else the seam will come apart in ~5 years.   And he cuts a 45° off the corner, as per code for a good lay on the next layer.   I watched this video several times, and it helped me succeed in this.

    When torching down to a wood deck you have to first fasten down a sheet of asphalt-impregnated fiberglass, to ‘fireproof’ the deck.   But as I was applying to eh, ‘fireproof’ shingles I wasn’t going to bother with that.   The volatile organic compounds in these shingles evaporated many years ago.   Laying directly on shingles may be a little bumpy, but the melt will help contour to them.   It’ll be fine for a house that will be torn down in 5 years for redevelopment.

    You can see that this roof has a built-in ‘rain gutter’.   IOW on the roof itself as it reaches the edge, it has a built-in trough, integral to the roof. (above)   This has been nothing but a nuisance as they always leak and ruin my soffits below, which I have to rebuild every two years or so.   So first thing, I am going to saw off the top half of the fascia, which will allow a fairly smooth slope of the roof all the way to the edge.   Here we are, with the ‘rain gutter’ sawn down and inverted shingles (Craigslist, free) to replace the old membrane’s wrinkles.   It got all the way up to a sweltering 78° on the roof that day…   I was sweaating…   (Click to enlarge)
    5. 22 Aug 2016
    Swept, with drip-edge installed, and ready!
    3. Swept and flashed

    I started the torch-down process at the back of the house, on a small building projection which is the master bath.   It was here that I found out I can do this.   It’s short courses, in the back where all my sins will never be seen, although it’s also the most likely place to set the house on fire, being partly under the eaves.   I have a big halon fire extinguisher to hand, and shield the wood with all I have available, a kevlar tarp.   The torch came on way too high so I had to regulate it all the time using the trigger.   Painful and erratic.   Needed to experiment with the propane regulator and bottle valve, and finally got the pressure down to just right.   Used alot less propane too.   My tool for unrolling the membrane (straight hoe) was damaging the soft modified bitumen, so I’d have to make a special tool.
    2. Bathroom - second course

    b. Roof jackNow for the jacks.   For torch-down, I didn’t know whether jacks should be treated like they are with shingles, with the lower edge exposed?   So I put a silicone bead on the underside, around the periphery.   Why the periphery and not around the riser?   Because the idea is to keep water out.   If I’d siliconed around the riser, if water gets under the flashing it would sit there and rust most of the assembly, whereas with the silicone bead around the periphery water is kept substantially away from the metal.   You can see the silicone squeezing out.   a. P-jackFor the roof-jack on the stink-pipe, I’d heated the membrane thoroughly so it would stick to the underside of the jack, but after it was over I decided the flashing must be completely under the membrane, as there’s the thickness of the lead that could let in water otherwise.   I siliconed it well in any case.   Same with the P-jack for the chimney flue.   (Why is it called a P-jack?   Nobody knows…)   Screws to hold down the flashing, in or outside the silicone bead.

    c. Vent holeNext was the first attic vent.   These help release the hot air in the attic, to make it easier to keep the house cool in Summer.   d. Vent onWhen I removed the old vent over the bathroom, I found there was the bathroom fan pipe there as well, so I stapled it to one side to reduce the edges that impair air flow.   Also I cut the opening larger to take full advantage of the 8″ stack in the new vent.   Your new vents must be metal if you are torching-down.

    Then I prepared that under-gable which is very likely to catch on fire with the operation I was doing, so I stapled in this kevlar sheeting I had handy.   But the joke was on me.   Turned out that it simply melted at the temps I was using.   Well, so far it seems I haven’t left any embers in the wood to burn the house down.e. Under gable

    f. Measure-cutTo cut the sheets of modified bitumen I used what turned out to be an expeditious shortcut.   I measured the length I needed, then folded over the end and based my cut on that.   No need for a sheetrock square, as long as I made my cuts fairly straight.   The hook-knife utility blades I bought for this turned out to be a godsend.

    Ok, ready to torch.   Notice the custom tool I made using a half-joint of electrical conduit, and the exactly-right bend.   I bought rubber tips, and these turned out to be just the ticket.   The torch and propane tank were rented at Aurora Rents for $18/day, a bargain I think.   Of course I had to pay to top up the propane when I took the rig back, but I’d set the regulator very sparingly so with two days’ work I’d used just a gallon out of the five in the tank!
    g. Ready to torch
    Ok, all done with the bathroom projection.   It’s not the prettiest in the world, but it is waterproof, and I know what I’m doing now.
    h. Bathroom

    Time for the first course on the main roof.   Notice I’d put down the dripedge flashing already, so the melted bitumen would stick to it and seal.   And notice I’d rolled back this roll while it was hot, to show the adhesive effect.   It sticks pretty uniformly as long as I get it not too hot, not too cold.
    i. First course

    What this doesn’t show is how dreadfully I’d lined up the roll.   I only unrolled it 10′ for alignment (out of 33′), and by the time I got to the end of the roll it was overhanging the edge by 4″.   This, even though I’d corrected it after 10′ making a terrible wrinkle.   It is definitely not easy to get these damned rolls straight.   I finally figured out that I must have at least as much weight in the rolled-out alignment segment, as I have in the roll to be torched down.   This means I must unravel a roll at least half-way in order to get a decent alignment.

    But the good news is, I’m pretty good at hiding my mistakes:
    j. Third course

    You can’t see it here, but the first and third courses were zig-zagging all over the place, but I managed to compensate.   Heat across, pull, heat the other direction, pull — stepwise, not a continuous unroll.   If you click to zoom you can see some places along the edges, where I’d overheated the membrane and the asphalt bled out the seam, but I saw it as I was doing it and reduced the heat.   Just like in Dude’s video above, a little yellow flame at the roof surface is just right, but not too much.   A little flame indicates that the extremely-thin polyethylene sheet has evaporated, and we’ve reached the bitumen.   Alot of yellow flame means we’ve melted half the thickness!   This is a key Tell.

    Notice in the foreground above where in the middle course I’d joined another roll.   As it showed in Dude’s video, I heated the surface of the finished roll until the rock granules started spalling and the bitumen came to the surface.   Then I heated down the next roll and it stuck real well, although the interface isn’t very pretty.

    I started each roll at the back of the house, so the blackest line of these seams would be hardly visible from the front of the house.

    Ok, now I have it high enough to finish off the bathroom projection peak with a cap-sheet.   I heated and laid this down by hand, rather than rolling it.   During torch-down I wore a leather glove on my left, but discovered quickly that I’d already worn a hole through the end of the middle finger, when I got molten asphalt on it.   Apparently I use that finger alot…k. Bathroom finished

    And so I kept torching down rolls like there’s no tomorrow.   It’s actually pretty easy once you know how to set up, what you’re looking for, and if you pay attention.

    I doubled the number of attic vents, making them 8′ apart;   I tried to explain to the tenant how this benefits them, but ehm, she’d been using her ‘Medical MJ’ so I was unsuccessful…

    The course that involved all the vents across, was especially troublesome.   I couldn’t just unroll the roll, as the vents were in the way.   So I unrolled it below the vents, and made the cuts for the vent stacks there.   Then I slid the course up into place and it fit the vents.   Now what?   I pulled the bottom edge of this course up over the vents and torched that down, 6′ at a time.   Then above, in between the vents I pulled down the membrane between them and torched those down individually, from the center outwards.   I got it as comprehensively glued as I can figure out is best possible.   As a precaution I thoroughly siliconed around each vent as well, to seal it with prejudice and alacrity.l. Full slope

    I figured out why roofers don’t buy that gravel to sprinkle in the hot tar anymore.   It’s much cheaper to just paint;   it actually sticks and it looks great.   Who knows how long it will last, but I used good Rustoleum with that finger-trigger doo-dad. (color:   Soft Gray Iron)
    m. Full slope painted

    And from t’other direction.   I ran out of membrane about 8′ from the very end of this slope.   But at least 6′ of that is overhanging the front porch, so it can wait ’till after the Monsoon Season.
    n. Full slope East

    But I think this turned out very well.   Going back up on the roof the next day, I found that the surface was much harder than it had been as a roll of modified bitumen.   “Modified bitumen” is a special mix of rubber, and asphalt.   When you treat rubber with heat, in the presence of sulfur, it will ‘vulcanize’ making it hard, like car tires.   I think this may be happening to a limited degree here.

    o. Chimney detailFinally, there’s the wood stove chimney with that P-jack.   Well it’s not complete without a ‘storm collar’, which is a skirt that fits around the flue to shed off rain.   I couldn’t find this special part anywhere, and I thought I’d have to buy a $25 sheet of tin to make my own.   But fortunately an elderly guy at Lowes suggested I go to Rich’s on Aurora Ave, which sells hot tubs, BBQ pits, etc, and by Jove they had exactly the storm collar I needed for an 8″ flue.   It’s important to silicone around where the skirt meets the flue.   Unfortunately the chimney cap is for a 10″ flue, but that will just have to suffer for now…

    ,'after' => '

    ') )