Single-ply roofing is a common choice for commercial buildings in Williston, ND, and it is one of the core services Mid-West Roofing Systems offers as a locally owned and operated commercial roofing contractor. The three main membrane types are TPO, PVC and EPDM. The right one for your building depends on what the roof deck and insulation look like today, how water leaves the roof, how the membrane will be attached, and how often people and equipment work up there. This article walks through those questions so you can compare options on the building’s conditions rather than on a list of general benefits. For a conversation about your roof, call (701) 500-9399.
What single-ply membranes have in common
A single-ply system is a factory-made sheet of flexible membrane installed over insulation and a structural deck. Because the sheets are manufactured in controlled conditions, thickness is consistent, and the field work comes down to attachment, seams and flashing. That is where most of the differences between roofs show up, and it is also where most problems begin.
Unballasted single-ply systems can be lighter than some built-up or ballasted assemblies, which can matter on older buildings with limited structural capacity. White TPO and PVC membranes reflect more sunlight than dark EPDM, but reflectivity is only one factor in a place like Williston, where winters are long and a roof spends months under snow, freeze-thaw cycling and wind. How much any membrane lowers energy costs depends on the building, its insulation and how it is used, so it is best treated as something to evaluate rather than assume.
The three membrane types compared
| Question | TPO | PVC | EPDM |
|---|---|---|---|
| Typical surface | Usually white or light | Usually white or light | Usually black |
| How seams are made | Heat-welded | Heat-welded | Adhesive or seam tape |
| Often considered when | A reflective, welded system is wanted for a general commercial roof | Grease, oils or exhaust discharge may reach the roof, such as near restaurant or process vents | Large, simple roof areas where long sheets limit the number of seams |
| Repair approach | Patches welded to clean membrane | Patches welded to clean membrane | Patches bonded with compatible adhesive or tape |
Treat the table as a starting point. Manufacturers formulate each membrane differently, so a specific product’s data sheet and installation requirements should always back up the choice.
A suitability checklist for your building
Substrate and insulation
Single-ply membranes are only as sound as what sits under them. Wet insulation, a deteriorated deck or an incompatible old layer can undermine a new membrane, and trapped moisture is hard to see from above. The contractor should confirm what the existing roof is made of, whether a recover over it is acceptable or a tear-off is needed, and which insulation boards and cover boards the chosen system is designed to go over.
Drainage and slope
Flat commercial roofs depend on drains, scuppers and slight slopes to move water off. Persistent ponding after rain or snowmelt warrants drainage investigation; acceptability and warranty requirements depend on the specified system. If a roof holds water, the plan may need tapered insulation, added drains or deck repairs before a membrane choice means much.
Attachment method
Membranes can be mechanically attached with fasteners and plates, fully adhered to the substrate, or held down with ballast. Wind exposure, building height, deck type and roof shape all influence which is appropriate. Williston sits in open country, so wind uplift at corners and edges is a real design point to review with the installer rather than leave to a default.
Rooftop activity
Roofs that carry HVAC units, vents, satellite equipment or regular service traffic need more protection than a roof nobody visits. Walk pads, added protection under equipment and sensible service routes can save the membrane from punctures. If a tenant, a refrigeration contractor or an HVAC company is on the roof every month, say so during planning.
Detailing and flashing
Leaks can develop at seams and details as well as in the membrane field. Walls, curbs, penetrations, drains and corners all need properly formed flashing, and the contractor should be able to explain how each one will be handled and sealed on your roof.
Service access and future repairs
Think about who will maintain the roof over its service life. Heat-welded systems and adhesive-seamed systems are repaired differently, and a patch must be compatible with the membrane already in place. Ask which repair method applies and what documentation you will keep with the building file.
Working with Mid-West Roofing Systems
Mid-West Roofing Systems serves commercial buildings in Williston and across North Dakota, South Dakota and Minnesota, and single-ply installation covering TPO, PVC and EPDM is among the company’s listed commercial services. A good project begins with an assessment of the roof’s actual condition so that repair needs, drainage and moisture are understood before a system is chosen, and a roof that is already leaking may call for emergency roof repair first. If an existing membrane is sound but weathered, a restoration approach such as commercial roof coating may be worth comparing against a full replacement. Owners looking at other membranes can also review the company’s single-ply roofing overview for North Dakota and South Dakota or review a spray foam roof as a distinct system choice where the building conditions support it.
Whatever system you consider, ask for the scope in writing: the existing layers to be removed or kept, the insulation and cover board, the attachment method, the flashing details and the repair method for later maintenance. Those items let you compare bids on equal terms, which is more useful than a general promise of savings or durability.
Frequently Asked Questions
Which single-ply membrane is best for a Williston commercial building?
No single membrane wins everywhere. TPO and PVC are welded and light-colored, EPDM is black with adhesive or taped seams, and the best match depends on the substrate, drainage, attachment method, rooftop equipment and any grease or chemical exposure.
Can single-ply be installed over an existing roof?
Sometimes. It depends on the condition of the existing layers, whether the insulation is dry, and whether the manufacturer’s system allows a recover. A roof assessment should settle recover versus tear-off before pricing is compared.
How are leaks repaired on a single-ply roof?
The repair has to suit the membrane. Welded membranes such as TPO and PVC are patched by welding, while EPDM uses compatible adhesives or tape. Finding the true source, often a flashing or seam detail, comes before any patch.
What should be in a single-ply roofing proposal?
Look for the existing roof layers, insulation and cover board, membrane type and attachment method, flashing details at curbs and penetrations, drainage corrections, and how future repairs will be handled.