Drain Replacement & Installation
A Clogged Drain is a Roof’s Worst Enemy
When water sits on a roof too long there’s likely something wrong with your drains. If you have ponding water that doesn’t go away after it rains, give us a call right away.
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The Price of Ponding
Why Ponding Water is Destroying Your Flat Roof
Every day water sits on a flat roof, it accelerates membrane breakdown, opens seams through freeze-thaw cycles, and adds structural load the deck was never designed to carry. By the time the leak shows up inside the building, the damage has been compounding for months.
In this walkthrough, Kirby Hewines shows you what ponding water actually does to a commercial flat roof, why drain replacement and new drainage installation are the only real fix.
Want to know your roof’s condition? Start with a FREE Roof Condition Report to find out exactly what’s going on.
50+ Point Roof Inspection
by commercial roofing experts
Photo Documentation
of all wear, damage, and deterioration
Detailed Summary of Defects
with prioritized action items and cost estimates
Why Flat Roofs Flood
Common Causes to Ponding Water on Flat Roof Systems in Ontario
CAUSE 1
Drains set above the membrane
When a drain bowl sits higher than the roof surface around it, water has to rise before it can exit. That guarantees standing water around every drain after every rainfall.
CAUSE 2
Not enough drains for the roof size
Too few drains, or drains too small for the square footage, cannot move heavy rainfall fast enough. Water backs up across the roof faster than the system can clear it.
CAUSE 3
Clogged strainers and drain lines
Leaves, gravel, sediment, and biological growth restrict the inlet and the line below it. The drain still looks open from above but moves a fraction of the water it should.
CAUSE 3
Deck deflection and low spots
Flat roof decks settle over time and insulation compresses under equipment loads and foot traffic. New low spots form away from the existing drains, and water collects where the original slope no longer reaches.
Drain Replacement
We remove the failed drain assembly, cut back the membrane, install a new cast iron or aluminum drain bowl set flush with the deck, and re-flash with compatible membrane plies. The new drain sits below the surrounding field, so water actively moves toward it instead of pooling around the old high spot.
New Drainage Installation
When the existing system is undersized, we add primary drains, secondary overflow drains, or through-wall scuppers sized to the roof area and the local rainfall intensity. This is the work that turns a chronically ponding roof into one that clears itself within hours of a storm.
Tapered Insulation and Re-sloping
Where the deck has settled or the original slope was never adequate, we install tapered polyiso to direct water from the low spots toward the drains. Often paired with new drainage installation when a single section of roof needs both more capacity and a better path to it.
See Tapered InsulationIS YOUR ROOF Not DRAINING?
Early Signs of Drainage Failure
Standing water 48 hours after rain
Debris and nesting blocking strainers
Moss or algae growth around drains
Bubbling or blistering around penetrations
Visible membrane pulling away from bowls
Want us to check your drainage system?
Before
After
Hover to see the finished result
Tap to see the finished result
effects of standing water
Don’t Let a Drainage Problem Become a Replacement Problem
A flat roof with proper drainage lasts 25 to 30 years. The same roof with chronic ponding rarely makes it to 15. That difference is the cost of a full membrane replacement, the disruption to tenants, and a capital expense that lands a decade earlier than the building was planned for.
Drain repair is the cheapest intervention on the entire roof, and often the one that buys back the most years. See other ways we help property owners and building managers cut costs through preventative maintenance.
Spend Less on RoofingStanding water exposes the membrane to constant UV and moisture, breaking it down years faster than the dry sections of the same roof.
Water trapped in seams freezes overnight, expands by 9 percent, and pries laps and flashings apart. Ontario winters do this 40+ times a year.
One inch of standing water weighs 5.2 lbs per square foot. Two inches over a 5,000 sq ft section adds over 50,000 lbs the deck was never designed to carry.
Added weight causes deflection, deflection deepens the bowl, and the damage accelerates toward a premature roof replacement.
Drain Replacement Projects
Recent Work from the Videl Team
How much does drain replacement or drainage installation cost?
Drain replacement and additional drainage installation typically run between $650 and $1,250 per drain, depending on the drain type, roof material, accessibility, and the condition of the surrounding system. Larger projects involving multiple drains, scuppers, or re-sloping are quoted separately. For a precise number on your roof, book a free assessment and we’ll give you a fixed quote based on the actual scope.
What happens if I keep ignoring the ponding?
The damage compounds quickly. Membrane breakdown, freeze-thaw seam failure, and deck deflection eventually force a full replacement years before the roof should have needed one. Our blog post on why flat roofs fail walks through the progression in detail.
What’s the difference between fixing drainage reactively and planning for it?
Reactive drainage work usually means responding after a leak has already caused interior damage. Proactive work catches the ponding before the membrane fails. The cost difference is substantial, and we break it down in our article on reactive vs. proactive roof maintenance.
Will I need a full roof replacement or just drainage repairs?
That depends on what’s underneath the standing water. If the membrane and insulation are still sound, drain replacement or new drainage installation is usually enough. If saturation has reached the deck, more extensive work may be needed. Our free 50-point roof condition report tells you exactly where your roof stands.
How quickly can Videl respond to a ponding water emergency?
For active leaks tied to drainage failure, we guarantee a 90-minute on-site response across the GTA, Niagara, Hamilton, and Halton. For non-emergency drainage assessments, we typically book within a few business days. See our emergency roof repair page for details on our response guarantee.
