7-Point Quality Checklist for Johns Manville Roofing and GoBoard Projects

I review every installed system before it reaches the customer—roughly 400 site inspections a year. In Q1 2024, I rejected 12% of first deliveries because the work didn't match the approved spec. Not catastrophic failures, mostly small stuff: wrong fastener, skipped edge prep, a sealant that looked right and wasn't. This is the 7-point checklist I run on commercial roofing and tile-backer jobs, and it's built around a simple idea: check the details you don't think will fail, because those are the ones that fail.

Who should use this checklist?

Commercial roofers, insulation crews, tile installers, general contractors, and anyone who has to sign off on a waterproofing or roofing installation. If you quote from memory, this will catch you. If you think the manufacturer's detail drawings are for the other guy, this is for you.

The 7-point checklist

Step 1: Pull the current Johns Manville roofing details, not the old folder

The roof retrofit in November 2022 changed how I think about spec matching. The general contractor used a 'temporary' sealant because the specified material was backordered. I knew it was wrong, but I didn't push hard enough. Eight months later, the parapet cap leaked. So before you write a specification or approve a roof layout, open the current Johns Manville roofing details. Not the PDF you saved last time—the current set. I've watched a competent contractor install 20 squares of TPO with a curb detail from 2021. The 2023 revision changed the metal cap flashing. If you're working from memory, you're not working from the spec.

Step 2: Verify the substrate and do a real surface prep

Substrate conditions matter more than the membrane brand. I check for moisture, dust, grease, and any little islands of cured sealant. On smooth surfaces, I carry a can of Sprayway glass cleaner for spot cleaning. It cuts grease and leaves no oily residue, which is exactly what you want before a peel-and-stick flashing. But it's a spot cleaner, not a substitute for a broom or a pressure wash. I've rejected a roof because the installer tried to wipe a soiled membrane edge with a rag while the substrate underneath was still dusty. Clean the substrate first, then spot-clean with something like Sprayway, then flash.

Step 3: Check the Johns Manville GoBoard layout before any tile goes up

I'm a fan of Johns Manville GoBoard for waterproof tile backer because it changes the sequencing. But the layout still deserves inspection. Fastener type, spacing, and joint direction all affect whether the board floats or locks. I run a straightedge over every seam. If a screw bugles the surface or a joint isn't flush, I don't care how good the tile setter is—the tile will show it. The current GoBoard installation instructions are not a suggestion. I learned that the hard way when a fastener was driven too deep and tore the face layer. We didn't have a formal torque check in our install process at the time. The third time it happened, I finally created a checklist. Now it's on every phase.

Step 4: Match transitions and penetrations to the detail drawings

Roofs and showers share one principle: water finds the transition. On a roof, inspect corners, curbs, parapets, and every penetration. On GoBoard, inside and outside corners and niches are where waterproofing decisions happen. If the current Johns Manville roofing details call for an L-shaped metal flashing, don't substitute a caulk bead. In a shower, use the manufacturer's corner reinforcement or the equivalent product in the current JM guide. I've rejected more jobs for sloppy corners than for any other single reason. A straight wall with a messy corner isn't a detail issue—it's a future water issue.

Step 5: Prep insulation edges with a foil shaver (the step everyone skips)

This one is my pet peeve. If you're working with foil-faced fiberglass duct board and you seal directly over the foil facing, you're depending on a surface that's designed to release. That's exactly why a foil shaver exists. It shaves back a clean band of foil along the cut edge, exposing the fiberglass core so your mastic or tape has something to bond to. The first time I saw a duct joint peel open in an auxiliary gymnasium, the installer had used a utility knife to 'score' the facing instead of a foil shaver. He was saving a two-minute step. It cost him a callback. If you don't have a foil shaver, get one before the job starts—don't improvise with a straightedge and a blade.

Step 6: Check fasteners and flatness with your hands, not your eyes

I carry a 6-foot straightedge everywhere. You'd be surprised how many seams look flat until you run a straightedge along them. For GoBoard, I look for fastener heads that are driven flush—not so deep that they tear the face paper, and not so high that they create a hump. On duct board, I check that the foil shaver run didn't cut into the fiber core too deep. A clean, true edge is what makes the next step work. The visual check catches obvious problems; the straightedge catches expensive ones.

Step 7: Document with photos and a signed checklist

Finally, take photos of every critical detail before it is covered. I know it feels like paperwork. But when a building gets a leak in 18 months, photos answer questions that no one can answer from memory. On one job, a photo of the foil shaver pass saved the insulation contractor from a warranty claim. They had clear proof the edge was prepped. Without it, they'd have been liable. Create a simple checklist, sign it, and keep the photos in the project folder. It's the least glamorous step and the one that pays off.

Cost reality check: drywall versus GoBoard

I also hear this question a lot: 'how much is a sheet of drywall?' Usually it comes from someone trying to budget a tile job. If you asked me in March 2025, a stock 1/2-inch 4x8 drywall sheet typically runs somewhere between $12 and $18, depending on region and whether you're buying at truckload pricing. But if you're comparing that to a waterproof tile backer, you're comparing the wrong things.

Here's my view: price per sheet only matters at the supply store. The number that matters is the installed cost of the assembly. With drywall in a wet area, you need green board or a separate waterproofing membrane, plus more labor and more steps. GoBoard costs more per sheet than drywall, but it combines the substrate and waterproofing in one board. I've watched a $10 savings on backer board turn into a $250 fix plus a schedule delay when the waterproofing liner had to be torn out and redone. So ask how much is a sheet of drywall if you want. But also ask what else has to be installed on top of it before it can survive water. The cheapest board is not cheaper when it requires a whole extra system.

Common mistakes to avoid

Over the last four years, I've seen the same mistakes show up again and again. Using outdated JM roofing details is the most common, and it's also the easiest to prevent. Skipping the foil shaver on duct insulation is second, because the failure shows up months later. The third mistake is treating surface prep as optional—that's where Sprayway glass cleaner or any good spot cleaner belongs, but only after the substrate is actually clean. And the fourth is buying on sheet price instead of installed cost. All four come from the same mindset: the detail will be fine. Once you accept that details fail, this checklist becomes routine.

Every time a roof or shower fails, it fails at a detail: a corner, an edge, a fastener, a contamination spot. This checklist is just a way to force you to look at those parts before they're hidden. Update your JM details. Shave the foil. Clean the surface. Write it down. Then the next inspection—mine, or your customer's—becomes a formality.