Adventures in Garage Roof Replacement

This fall, Cathie and I, along with our neighbors Jim and John replaced the roof of our garage. Our house is part of a two unit condo and the garage is a shared structure, so it was a joint effort.

The old roof had been leaking for quite a long time -- at least since we bought the place in 2012 and probably long before that. As a result, there was damage to the underlying wall and roof structure that needed repair. This too was part of the project.

When the project started, I knew it would be a fair amount of work, but in the end (as usual) it was substantially more than I anticipated. Still, at the end of the day, we got a good result and I'm quite satisfied. Many thanks to Cathie, Jon and Jim for all their help and hard work!!

Here are some pictures (and associated commentary) describing the process (and the difficulties we encountered/overcame along the way).

Removing damaged blocks from the back wall.

Over the years, the leaking roof had caused substantial water damage to the rear wall's window-framing and concrete blocks. So to start, I bolstered the rafters, removed the damaged window framing and concrete blocks.

The window and wall after repairing the damaged blocks and framing.

I replaced the bad blocks and re-framed the window. I also repaired (with mortar) other blocks along the wall that had superficial (but non-structural) damage. The end result looked reasonable good.

(Detail: Fitting the blocks into spaces where there were existing blocks above and below the space, proved a bit tricky when it came time to mortar. In the end, I used little dowel pegs to space the block in place, then pushed mortar into the cracks to get a good tight fit.)

Next, I moved onto the roof itself. The garage roof had two different sloped surfaces. One side had a reasonably steep slope, the other shallow (1.5" over 12"). The old roof had shingles on both slopes, which was a bad idea. As I learned (via the Internet), shingles should not be applied on low sloped roofs, as the shingles do not provide adequate protection against water backing-up under the shingle. This indeed was the source of our water leak problem.

I considered several alternatives for the low-sloped part of the roof: PVC, EPDM, Modified-Bitumen rolled roofing. Eventually, I decided to go with Mod-Bit rolled roofing, because it looks good, and I felt it would be safer to walk on (especially when damp or icy). This "walkability" feature matters to me, since my daughter can easily access the roof from a doorway in her 2nd story bedroom.

For the steep slope, we went with conventional asphalt shingles.

Once we settled on a solution, I ordered the materials. The rolled roofing (and associated materials -- adhesive, caulk, etc) was surprisingly difficult to acquire. In the end, I went through a commercial supplier, who in turn, had to order supplies from the manufacturer. It took 3-4 weeks for the material to finally arrive. This caused some concern, since the rolled roofing can only be applied in temperatures above 50 degrees. In mid-September, when the project started, temps in New England are often above 50 degrees, but by mid-October, it starts getting colder and more rainy. For a while, I really started to wonder whether or not we'd get the project done before Spring.

Removing the first shingle of the old roof.

Once the materials showed up, we finally got started on the demolition. We rented a 15 cu-yard dumpster to hold the debris. For $350, we had the dumpster for a week, and could deposit up to 4000 lbs of waste.

To our surprise, there were 5 layers of old roofing to remove.

Removing the old roofing, was a bigger chore than expected. It took a day and a half to for John, Cathie and me to remove the old roofing on just the low-sloped side of the roof. It turns out, we had five, yes 5 layers of old roofing to remove! There were three layers of shingles and two layers of rolled roofing. It seems the original roof -- built in the 1920s -- was an asphalt rolled roof, then later came a shingle roof, then another rolled roof, then two more layers of shingles! In the end, we tossed more than 6300 lbs of waste into our dumpster. Yikes!

Reminants of the old chimney.

Demolition also involved removing an old chimney that was tucked into the corner of the garage.

The underlying plank roof decking.

As expected, the underlying plank roof decking had some damage.

I replaced the sill plate and reinforced some partially rotted rafters.

Removing rotted decking revealed some structural damage. The sill plate, rafters, facia board, and trim had damage, extensive in some places. So I replaced the sill plate, reinforced some of the rafters, and added a new facia board.

The new facia board, with Z-flashing to shunt water away from the top of the wall. 

I used a 2x6 for the new facia board and added Z-flashing to the lower edge in order to keep water off the top of the concrete wall. The old design used a 1x6 and had no drip edge, as a result, water would run off the facia and fall onto the top of the wall. This improvement should help keep water off the top of the wall. In retrospect though, I wish I had added some kind of rafters extensions to extend the roof further over the edge of the wall and give it a proper overhang.  This would have done an even better job of keeping water off the wall.

A look at the sill, rafter, and facia board repairs.

With the structural repairs done, we were ready to patch the roof deck and move on.

We replaced the rotted decking at the eaves with 3/4" plywood.

Unfortunately, the decking was made from old (1920's era) planks, whose depth (7/8") wasn't easily matched, so we ended up going with 3/4" plywood, with shims at the edge to smooth the transition. Moreover, even after replacing the worst of the rotten eave planks with plywood, we realized there were numerous gaps and voids in the remainder of the decking. The rolled-roofing specifications limited plank gaps to be no more than 1/4". To meet that spec, we'd have had to repair a lot of decking. Instead, we decided to apply a layer of 15/32" plywood over the entire surface. That was an unexpected expense (in time and money), but in retrospect, it was worth it.

John preparing for rain.

There was no way we were going to get through this project without dealing with some rain. We used bricks from the old chimney to hold down the tarp. It worked pretty well. Luckily we only had a few days of rain to contend with.

Applying the "Base" ply.

Once the rain passed and the new layer for decking was down, we started to lay down the first of three layers of roll roofing. This first layer is the "Base Ply", which was nailed to the underlying decking with 1-1/2" roofing nails through 2" tin disks.

John and me nailing down the Base-ply.

Successive strips of Base-Ply were overlapped by 2". 

Finished with the Base-ply.

(Details: once the job was done, we did notice a few little "bubbles" in the rolled roofing. These were traced back, not to the mid-ply or cap-sheet, but to this base-sheet. It seems, we should have been a little more careful to get this base ply down super flat with no "bubbles", since those bubbles in the end allow the mid- and cap-sheets to float ever so slightly above the deck, leaving "bubbles" that are visible at times. If I ever do one of these jobs again, I'll be sure to get the Base-ply is down nice and snug, with no bubble or wrinkles in the material.)

Layering on the mid-ply.

Next came the Mid-ply layer. The Mid-Ply is "optional", but it adds an extra layer of water protection. Since we want this roof to last a good long time, we figured it was worth the extra cost and effort to do a Mid-Ply. The Mid-Ply is "self-adhering", which means, it's like a giant sticker. You lay it out, then peal off the backing and press it into place (with rollers). We followed the manufacturer's instructions and didn't seem to have too much trouble. Still, it took time.

After putting down the mid-ply, we installed the edge flashing. Also, as recommended by the manufacturer, we sealed all the mid-ply seems with caulk-grade adhesive. This optional step (sealing the seams), turned out to be a messy hassle, since it put down a layer of caulk on the surface, which later, in spite of our best effort, we couldn't help but step in while we rolled out the cap sheet. (If I ever do this type of job again, I'll won't bother sealing the mid-ply seams with caulk. After-all, the seams are already sealed via the end/side-lap stick-on adhesive.)

Rolling out the Cap Sheet with a heavy roller.

Finally, came the 3rd and final layer -- the Cap Sheet. Like the mid-ply, this layer is also self-adhering, peel-and-stick. For the most-part it went down reasonable well. However, to avoid having too many end-laps, we rolled out full-garage-width 24-foot strips. These long pieces were tough to manage with just three of us (John, Cathie, and me). Also, as per the instructions, we attempted to put down all three layers in a single day. For us, the task was too big for one day. We pushed on as best we could, working a good 15 hour day; But by 10pm we finally called it, having only about half the cap-sheet on.

The next day, we picked up where we left off; swept the mid-ply clean, then continued laying down the last of the cap-sheet.

From start-to-finish, it took us about 20 hours to put down the 3-ply system (including flashing) for a 24' x 18' low-sloped roof. We probably could have finished sooner if we hadn't a) used a mid-ply layer, b) sealed the mid-ply seams with caulk, c) used (difficult to manage) full roof-width pieces.

(Detail: after the rolled-roofing sat for a few days, I inspected it for so-called "mole-holes". I found a few along the roof edge, where the cap-sheet overlapped the edge flashing. It turns out that, in places, we probably didn't let the metal primer adequately "flash-off" before laying down the cap sheet -- after all it was 10pm! what do you expect?! Anyway, by following the manufacturer's directions, the mole-holes were easily fixed -- by heating the surface with a heat-gun and re-rolling by hand the cap-sheet in that area. It worked great and I subsequently went around and heat-sealed the entire edge.)  

By the time the low-sloped (roll-roofing) side of the roof was done, I was exhausted. Luckily, we had a spot of rain in the forecast, so we covered the roof and took the next day off. We hadn't yet removed the old shingles from the steep-side of the roof, so we didn't have too much trouble protecting the exposed ridge with tarp.

Starting to lay shingles.

After a day of rest, we took on the steeper sloped side of the roof. This surface, at 6' x 24', is substantially smaller than the low-sloped side of the roof.

Here's a summary of the steps involved applying shingles to this side of the roof.

• Remove old shingles -- only 3 layers this time!
• Detach gutter-anchors in order to clear the deck.
• Install drip-edge flashing on the eave edge.
• Roll-out and nail-down new underlayment.
• Install drip-edge flashing on the rake edges.
• Re-align the gutter and re-attach the gutter hangers to the roof decking.
• Snap guide-lines for shingles.
• Cut and install the "starter course" of shingles along the eave edge.
• Install shingles (in triangular pattern) across and up the roof. 
• Install the ridge cap shingles.

We faced a few challenges on this part of the roof. 

• As before, the decking was made of wood planks. Nailing into planks turned out to be a hassle when installing the shingles. Call it Murphy's Law, but it seems that I couldn't help but hit a seam between planks when nailing the shingles. As a result, I often had to fight to get the nails into solid wood. If I had to do over again, I would have put a plywood cover layer over the original planking just to have a solid sheet to nail into.
• Rotten eave planking. In spots along the eave edge of the decking there was some wood rot in the planking. At the time, it seemed rather minor, and I decided not to replace it. However, when I installed the drip-edge and starter-course, I felt (at times) the softness of the old wood when nailing. In retrospect, I should have repaired the bits of plank that had rot in them. (Also, applying a cover-layer of plywood would have addressed this problem.)
• Keeping the shingles aligned. As we applied the shingles up the roof, it seemed that the guide-lines we snapped on the deck, didn't line up very well with the natural alignment inherent in the shingles. This gave me no end of fits for a while, until I realized that perhaps my chalk lines weren't all that straight. I eventually just went with the natural alignment suggested by the shingles, and stopped worrying about being *exactly* on my lines. Then things went better. In the end, it worked out fine.

It basically took us two days to do the sloped side of the roof: One day (ok, really a half-day) to remove the old-roofing and detach the gutter; And another (full) day to do the underlayment, flashing, and shingles.  I admit, I'm somewhat of a careful worker and this was my first time shingling. As a result, I was SLOW. 

The ridge cap shingles and the transition to the roll-roofing.

To blend the shingles into the rolled-roofing, I applied two layers of shingles to the low-sloped side of the roof, then added a layer of ridge cap shingles. 

The custom-built corner piece, used to blend the old-crown molding with the new. 

To finish the job, I had to add trim to the facia board on the back-side of the garage. Unfortunately, this little task wasn't so easy. We weren't able to find new trim that matched the pattern of the old (rotten) crown-molding. A custom woodworker, down the street, could make it for us; but it'd cost a couple hundred bucks. So after futzing around for a full day, I came up with a corner design that allowed me to blend the old with the new. Overall, I think it turned out pretty good.

In the end, it was a pretty big job. From start to finish it took more than a month -- much of that time involved research, planning, then waiting for materials! The actual works probably involved a half dozen long days (with multiple helpers). Nevertheless, I'm glad we did it. We certainly saved some $$ and I think we got ourselves a pretty good roof.

Here are some pictures of the finished product.

The new roof, as seen from the front of the garage.

The steep-sloped (shingled) side of the new roof. 

The low-sloped (rolled roofing) side of the new roof.

The new crown-molding trim and corner transition-piece on the back-side wall.

I'm happy with the new roof... and glad to be done! :)