Thank you for visiting our site! We noticed you are using a browser we no longer support. To have the best overall experience and avoid issues navigating the site, please click one of the supported browsers to the right to download the latest version for free:
Johns Manville's roofing division built its reputation on insulation manufacturing before it built out a membrane line, and that background shows up in how their commercial roofing systems get assembled - insulation and membrane specified together rather than as an afterthought.
Johns Manville's rigid insulation board products are a core part of their manufacturing history, which matters directly on cold-storage and food-processing roofs where R-value and thermal performance carry as much weight in the spec conversation as the waterproofing membrane on top. We factor that insulation-first background in when a job's priority is thermal performance rather than treat every manufacturer's insulation line as interchangeable.
Johns Manville's modified bitumen products cover both SBS and APP chemistries, which we spec on the older mill and manufacturing buildings around Nanticoke and Carbondale where an existing multi-ply built-up roof calls for a compatible cap sheet rather than a full tear-off to single-ply. Their modified bitumen line integrates with the layered roof history these older buildings tend to carry, similar to the approach detailed on our SBS modified bitumen page.
Johns Manville also manufactures the base sheets and flashing accessories to go with their cap sheet products, which keeps the whole assembly under one manufacturer's warranty rather than mixing components across suppliers on a retrofit job.
We size that against the specific retrofit's scope, since a small patch repair on an otherwise sound built-up roof doesn't need a full manufacturer-warrantied assembly the way a full cap sheet replacement across an entire roof does.
Their TPO single-ply line rounds out the product range for buildings where a full reroof to single-ply membrane is the better call than a modified bitumen retrofit - newer flex buildings and distribution roofs where a clean deck supports a standard TPO installation without the layered-history complications an older built-up roof carries. We spec Johns Manville TPO on those jobs the same way we'd evaluate any manufacturer's line, on gauge, reinforcement, and warranty terms specific to the building at hand.
Choosing between the modified bitumen retrofit path and a full TPO reroof usually comes down to what we find once we're actually on the existing roof. A built-up roof with a sound base and manageable moisture reading points toward the modified bitumen retrofit; one with saturated insulation or a compromised deck more often points toward starting clean with TPO instead.
Cold-storage facilities near the I-81 warehouse corridor need higher insulation values than a standard dry warehouse, and Johns Manville's board product range gives us more flexibility to hit a specific R-value target within a given roof assembly thickness than trying to stack insulation layers from a manufacturer with a narrower board range. We calculate the target R-value with the facility's refrigeration engineer or design team rather than assume a standard warehouse insulation package fits a cold-storage building.
Beyond insulation and cap sheet, Johns Manville manufactures the base sheets, flashing membrane, and detail accessories that tie a modified bitumen or TPO installation together at penetrations, parapets, and roof-edge transitions. Sourcing that full component list from one manufacturer keeps the assembly warranty intact in a way that mixing base sheet from one supplier and cap sheet from another can jeopardize.
On retrofit jobs over an existing built-up roof, that accessory range matters most at the tie-in points between old and new construction, where a mismatched flashing detail is more likely to leak than a flaw in the open field. We spec the full Johns Manville detail package on these jobs specifically to avoid that seam-between-systems risk.
For an owner comparing bids, a quote built entirely from one manufacturer's component list is worth noting against a bid that mixes suppliers to hit a lower number, since the warranty coverage behind each approach isn't equivalent even if the sticker price looks similar.
No, they manufacture both. Insulation is a core part of their product history, but their commercial roofing division also produces TPO and modified bitumen membrane systems.
It depends on the existing roof condition. Buildings with a compatible existing multi-ply roof often favor modified bitumen; buildings with a clean deck ready for a full reroof often favor TPO.
Sometimes, but matched-assembly warranties often require components from the same manufacturer. We flag that trade-off before mixing manufacturer components on any bid.
Warranty length depends on the specific system, product line, and our current certification standing with the manufacturer at time of bid. We provide current terms in writing on every quote.
We calculate the target R-value based on the facility's refrigeration requirements, often coordinating directly with the facility's engineering team, rather than applying a standard warehouse insulation spec.
Related Commercial Roofing
