Johns Manville Modified Bitumen on Ann Arbor's Older Roof Stock
Johns Manville is a Denver-based manufacturer and a Berkshire Hathaway subsidiary that produces a full range of commercial low-slope roofing products, and its DynaWeld and DynaBase modified bitumen lines in particular show up regularly on the multi-ply reroofs and recover projects we handle on Ann Arbor's older commercial and institutional building stock.
Johns Manville's Modified Bitumen Strength
DynaWeld and DynaBase are Johns Manville's SBS modified bitumen product lines, covering torch-applied and other application methods for base sheets and cap sheets used in multi-ply roof assemblies. Modified bitumen has deep manufacturing history at Johns Manville specifically, and that product depth shows up in the range of cap sheet finishes, granule colors, and base sheet configurations available for matching an existing roof assembly during a recover or partial-replacement project on an older Ann Arbor building.
On downtown Ann Arbor buildings and some of the older Michigan Medicine annex structures with existing multi-ply mod-bit roofs, matching a recover or repair to the existing system's application method and ply configuration is often more important than switching to a different membrane chemistry entirely, and Johns Manville's product range supports that continuity well.
TPO and Single-Ply Options
Johns Manville also manufactures TPO membrane for projects where single-ply is the better fit than a multi-ply mod-bit system , new construction, full tear-off reroofs, or buildings without the redundancy requirement that pushes a project toward modified bitumen. We evaluate Johns Manville's single-ply line the same way we evaluate any manufacturer's TPO: membrane thickness, fleece-back availability, and how it fits the specific roof's traffic and wind exposure conditions.
The company's broader manufacturing base , beyond roofing, Johns Manville produces insulation products across multiple building material categories , generally supports consistent supply chain depth, which matters on larger institutional projects around North Campus and the medical campus where a delayed material shipment can push a whole reroof schedule into worse weather.
- Modified bitumen lines: DynaWeld and DynaBase, covering base and cap sheet configurations
- TPO line: single-ply membrane in standard thickness and fleece-backed options
- Parent company: Berkshire Hathaway
- Headquarters: Denver, Colorado
- Manufacturing scope: roofing membrane alongside broader building insulation products
- Common use here: multi-ply mod-bit recover and repair work on older institutional buildings
Matching an Existing Mod-Bit Roof During Recover
When we're evaluating an older building's existing SBS mod-bit roof for a recover project rather than full tear-off, matching the new cap sheet's application method to what the existing base sheet can support matters for both performance and, where applicable, warranty continuity. Johns Manville's product depth in this category gives us more matching options than manufacturers with a thinner mod-bit line, which is part of why the brand comes up disproportionately often on this specific type of Ann Arbor project.
We still evaluate whether recover is the right call in the first place before getting to manufacturer selection , an existing mod-bit roof with widespread wet insulation or structural deck issues needs tear-off regardless of how well a new cap sheet could theoretically match the old system.
Insulation Products Alongside the Membrane
Because Johns Manville manufactures insulation across several building material categories beyond just roofing, its polyisocyanurate insulation and cover board products often get specified as part of the same assembly as its membrane, which simplifies compatibility questions the same way sourcing membrane and insulation from a single manufacturer does with any brand. On a full tear-off and replacement, we look at the whole assembly , deck, insulation, cover board, membrane, and accessories , rather than treating membrane selection as a decision made in isolation from everything underneath it.
On recover projects specifically, existing insulation condition sometimes limits which new insulation products make sense to add on top, and we evaluate that constraint before finalizing manufacturer selection for the insulation portion of the assembly, separate from whatever membrane manufacturer ends up chosen.
Selecting Johns Manville Versus Other Manufacturers
We don't default to Johns Manville on every mod-bit project; we compare its DynaWeld and DynaBase options against other manufacturers' modified bitumen lines on application method, cap sheet finish, and cost, the same way we'd compare TPO options across manufacturers. Where Johns Manville's specific product depth in mod-bit gives a better match to an existing Ann Arbor building's roof history, that's the deciding factor , not a standing preference for the brand.
Johns Manville Questions We Get
Is Johns Manville primarily a roofing company?
No , Johns Manville manufactures a range of building materials including insulation products across several categories, with roofing membrane, including modified bitumen and TPO, as one significant product segment.
What's the difference between DynaWeld and DynaBase?
Both are Johns Manville SBS modified bitumen product lines with different specific sheet configurations for base and cap applications; the right combination depends on the roof's existing assembly and the application method being used.
Does Berkshire Hathaway ownership affect Johns Manville's product quality or availability?
We haven't seen ownership structure translate into supply or quality issues on our projects; Johns Manville's manufacturing scale generally supports consistent product availability for the jobs we spec it on.
Is Johns Manville modified bitumen a good match for an older Ann Arbor building's existing roof?
Often yes, given the company's product depth in mod-bit configurations, but we confirm the specific match against the existing roof's base sheet and application method rather than assuming compatibility.
Does Johns Manville make products suited to occupied-building reroofs without torch application?
Yes, self-adhered and cold-adhesive application options exist within their modified bitumen line for situations where open-flame torch work isn't practical on an occupied building.