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Commercial roof leak detection that finds the real entry point
Commercial roof leak detection is about proving where water gets in, not where it lands. We trace and test the roof in stages, so the repair goes in once and in the right place.
- Free quote
- Central Auckland based
- Written scope before work starts
- Photos of what we find
Why the drip is rarely under the hole
On a metal roof, water that gets past a lap, a fixing or a flashing does not drop straight down. It runs along the underside of the sheet, follows a purlin, soaks along insulation or sarking, then falls wherever it finds a low point. On a big building that can be several metres from where it entered.
That is why so many leaks survive a round of patching. Someone goes up, finds the nearest lap above the wet ceiling tile, seals it, and the next heavy rain proves it was not the problem. Proper commercial roof leak detection works backwards from the stain to the actual opening.
Our commercial roof leak detection process
Testing from the bottom up means a positive result points to one area, not several.
Ask about the weather
Which wind direction, how heavy, how soon after rain starts. A leak that only shows in a strong easterly points to very different places from one that shows in any shower.
Read the inside
Stains, rust drips, wet insulation and water lines on framing show the path water has taken. We trace that path up towards the roof.
Water test in stages
We wet one area at a time with a hose, starting at the lowest point and working uphill, while someone inside watches. Each area gets time to show before we move on.
Confirm and record
When water appears, we know which area caused it. We photograph the fault, note its location on a roof plan, and explain the fix.
Common entry points we test
These are the places we check first on most business roofs.
- Side and end lapsCapillary action draws water between overlapping sheets, especially on low pitch roofs and where laps have lifted.
- FixingsA screw that has backed out or a perished washer leaves a small hole on top of the rib. One bad fixing can wet a large area.
- Penetration flashingsFlues, vents, pipes and plant supports. Sealant that has cracked or a flashing that was never dressed properly is a common entry point.
- Skylights and clear sheetsOld polycarbonate cracks and its laps with the metal sheets open up. See our skylight and flashing repairs page.
- Box and internal guttersIf an outlet blocks, water can rise above the gutter sides and run straight inside. Read more about box gutter repairs.
- Parapets and wall junctionsWhere a roof meets a higher wall or parapet, the flashing has to cope with water running down the wall as well as across the roof.
Moisture, condensation and other look-alikes
Not every wet patch is a roof leak. Condensation forms when warm, moist air inside a building meets the cold underside of the roofing, and on bare metal roofs it can drip like rain. Cool stores, kitchens, gyms and buildings with people working overnight are typical places for it.
Plumbing, air conditioning drains and blocked downpipes running inside walls can also look like a roof problem. Part of leak detection is ruling these out. Where it helps, we take moisture readings on linings and insulation to map how far water has spread and whether it is still wet.
If we think the cause is condensation or plumbing, we will tell you, rather than sealing a roof that is not leaking.
What helps us find your leak faster
- Photos of the inside damage, and of the roof if you can safely see it from the ground or a window
- When the leak started and what weather brings it on
- Whether the roof has been repaired before, and where
- Access details, such as roof hatch, height, and any fragile areas you already know about
- Times when testing inside would disrupt staff, customers or stock the least
None of this is essential, but it shortens the visit and helps us bring the right gear.
After the leak is found
Once the cause is confirmed, many leaks can be fixed straight away with new fixings, a resealed lap or a redressed flashing. If the test shows wider problems, such as rust at several laps, we put that into a written scope with photos. Corrosion is often the root cause of repeat leaks on older roofs, and our rusted roof repairs page explains how we decide between treating and replacing sheets.
Where it makes sense, we water test the same area again after the repair, so you can see that the leak has stopped before we leave site.
Commercial roof leak detection questions
How long does commercial roof leak detection take?
A straightforward roof with one suspect area can be tested in a few hours. Large roofs, or leaks that only show in certain wind directions, can take longer or need a second visit. We give you an idea of timing once we have seen the roof.
Does the leak need to be active for you to find it?
No. Water testing lets us recreate the leak on a dry day. Staining, rust drips and wet insulation also tell us a lot about where water has been travelling.
Could it be condensation and not a leak?
It can. Warm, moist air inside a building can condense on the cold underside of metal roofing and drip down, especially on cold mornings. If the drips appear without rain, and across a wide area, condensation is worth ruling out before anyone starts sealing the roof.
Will water testing damage anything inside?
We test in small, controlled stages and have someone inside watching, so testing stops as soon as water shows. We also agree with you beforehand what needs covering or moving.
Do you repair the leak once it is found?
Yes, as long as you are happy with the scope. Most leaks we find can be fixed on the same roof visit or a planned one soon after. Bigger issues go into a written quote.
Why do leaks often show up only in some storms?
Wind pushes water sideways and even uphill under flashings and laps. A roof can be dry in steady rain from one direction and leak in a strong easterly or southerly. That is why we ask which weather brings the leak on.
Other repairs we carry out
Rusted roof repairs
Cut edges, laps and fixings assessed, then treated or replaced sheet by sheet.
Read more
Warehouse roof repairs
Long span roofs repaired around your stock, staff and trading hours.
Read more
Skylight and flashing repairs
Clear sheets, plant penetrations and flashings sealed and made watertight.
Read more
Box gutter repairs
Internal gutters, outlets, sumps and overflows cleared, repaired or relined.
Read moreGet your leak traced properly
Tell us where the water is showing and when. We will plan the testing and give you a free quote.
Get a free commercial roof repair quote
Tell us where the property is and what you need. Prefer to talk? Call 027 929 6889.