ROOFNOW™ Ontario Roof Retrofit Planning

Replacing Built-Up Roofing with Metal in Ottawa, Ontario

Convert an aging built-up roof only after confirming moisture, slope, drainage, deck and whether a sloped metal assembly is technically appropriate.

Local retrofit context: Ottawa is part of Ottawa and the National Capital area, where urban, suburban and heritage-neighbourhood roofing experience cold winters, significant snow, ice events, humid summers and sharp seasonal temperature changes. Nearby communities include Kanata, Nepean and Orléans. Installed cost is shaped by the complete roof assembly, not by field panels alone. Existing layers and field conditions should be verified before the final metal system is ordered.

Understand the complete existing assembly

Built-up roofing may contain multiple asphalt layers, felts, aggregate, insulation and repairs. Moisture can travel laterally and remain concealed. A metal replacement may require a new sloped structure or a different low-slope metal system rather than simply fastening panels over the existing surface.

A reliable scope separates investigation, removal, temporary protection, structural or deck repair, underlayment, permanent metal and restoration of adjacent walls or drainage. It also defines how concealed changes are documented and approved.

Conditions to examine

Number and type of roof layers
Moisture in insulation and deck
Existing slope, drains and parapets
Structural capacity for a new assembly

Retrofit mistakes to avoid

Trapping wet layers beneath new framing
Assuming visible ponding shows all low points
Fastening through unknown build-up
Removing aggregate without a containment plan

Inspect before choosing the replacement

Review cores or selective openings as appropriate to confirm layers and moisture. Map drains, scuppers, curbs and ponding. Interior staining alone cannot show the full wet area, so scope should allow for concealed discoveries.

For a built-up or tar-and-gravel roofing project in Ottawa, record roof zones, slopes, penetrations and prior repairs with photographs. Surface appearance alone cannot confirm the deck, moisture or attachment beneath it. The quotation should state the investigation completed and the assumptions that remain.

Plan removal and daily weather protection

Aggregate and asphalt require controlled handling and site protection. Divide the roof into weather-manageable zones and protect occupied space below. Any suspect material should be evaluated through the appropriate project-specific process before disturbance.

Agree on material access, debris containment, landscaping protection and the area that can be safely opened each day. Temporary dry-in needs positive laps, secure terminations and drainage. It should not become an indefinite substitute for the permanent roof.

Prepare the deck and roof enclosure

After removal, verify structural deck, slope and attachment. Wet insulation and deteriorated materials must not be encapsulated. If a new sloped metal roof is proposed, coordinate framing, ventilation, fire and drainage as a complete enclosure design.

Before covering the substrate, verify flatness, fastening, dry condition and all required blocking. Coordinate insulation, air sealing and ventilation where the opened roof makes deficiencies visible. Photograph the prepared deck and concealed repairs for the closeout file.

Build new transitions instead of copying old ones

Parapets, walls, drains and rooftop equipment need new elevations and flashings. Preserve emergency overflow and service access. The detail should allow future membrane or metal work without dismantling unrelated building components.

Eaves, rakes, valleys, walls, chimneys and penetrations must match the selected system and finished assembly thickness. Confirm measurements after demolition where conditions were concealed. Future service should not require destructive access to unrelated roof areas.

Quotation and closeout checklist

Identify every existing roof layer
Define removal and disposal limits
Describe deck-repair authorization
Name the exact metal system and finish
Detail flashings, drainage and ventilation
Provide photographs and product records

Compare proposals using the same boundaries. Clarify permits or project-specific reviews, temporary protection, site cleanup, wall restoration, accessories and exclusions. At closeout, inspect the complete roof and keep surplus material, colour codes, warranty information and concealed-work photographs.

Frequently asked questions

Can metal be installed directly over built-up or tar-and-gravel roofing?

Sometimes an overlay may be technically possible, but only after confirming layers, moisture, substrate, attachment, slope, edges and product requirements. This page does not replace a site assessment.

When should final metal measurements be taken?

After the substrate and critical transitions are verified. Concealed conditions can change plane lengths, edge heights and custom flashing dimensions.

What should homeowners keep after the project?

Keep the proposal, change records, product identifiers, warranty documents, deck and flashing photographs, care guidance and labelled surplus material.

Plan the replacement from the deck outward

ROOFNOW™ can assess the existing roof and prepare a project-specific permanent metal-roof scope.

Visit ROOFNOW™ Roofing Specialists

Planning note: General educational guidance only. Confirm structure, materials, moisture, disposal, product requirements and project-specific approvals with the responsible professionals and authorities.

Your Metal Roofing Estimate

From your first request to planning the installation, ROOFNOW™ makes every step clear and straightforward.