Leak at a vent pipe on a kliplok colorbond roof in Campsie Sydney

I like roofs that have no holes cut into it. It is an easy way of ensuring a leak free roof.

But this will mean that I am out of a roof repair job….

…So, fortunately for my roof repair business, people cut holes on colorbond roofs. They cut holes to put vent pipes through, install skylights, mount roof top air conditioners and install whirly birds.

And whenever there is a hole cut into a colorbond roof…there is a potential for a leak.

There is this colorbond kliplok roof in the Sydney suburb of Campsie that recently presented a real challenge to me….

vent pipe on kliplok roof leaking

tricky leak to find at the vent pipe


When we investigate roof leaks, we go through a process of elimination.

On this particular roof, there was the obvious PVC vent pipe which was located above the leak.

Then there may have been a problem at the upstream end of the roof sheeting because either the flashing was leaking, the turn-up was inadequate, or there is debris causing overflowing…

So, we cleaned the old sealant off the dektite flashing around the PVC vent pipe and re-sealed it. When it rained again, the leak was still there!

Then we went back to pull apart the upstream flashings. The upturns were not quite right (and we found that the blanket insulation was damp) – so we fixed these and cleared away the debris that had built up under the flashing. We waited again and the next report was that the roof leak was still there!

Capillary action lets water do amazing things. It is the only thing that can make water flow uphill!

So, in the design of metal roofing, great pains are made to combat the results of capillary action where the roof sheets overlap one another. The edge of the roof sheets are designed to prevent capillary action from drawing water over the lapped rib PLUS there is a catchment lip added on in some profiles to catch any water that manages to get over.

Kilplok roofing sheets rely mainly on grooves to prevent water climbing over the lapped rib.

Alarm bells sound when my guys see a vent pipe (or any roof penetration) cut into the area where two roofing sheets lap. This means that the catchment lip has been compromised and a leak could be happening…

Yet in this instance, the PVC vent pipe penetration hole was cut neatly beside the overlapped rib – so no potential problem there….

Finally, drastic action was needed. The roof sheeting had to come off!

It is quite easy for a screw fixed roof to take a roof sheet off . But a kliplok roof is a different matter. There are no screws. Extreme care has to be taken not to damage the roof sheeting because the concealed clips holds the roof on tightly. Usually, it is impossible to remove without causing some damage.

…Anyway, we managed to lift the lapping sheet up a bit to investigate what was happening.

What we found was that capillary action was up to her old tricks again. It was allowing water to seep along the lap – which allowed it to travel past (by going under) the dektite vent flashing seal!

It was another gem to put into our database of “why roofs leak”.

Check out the video below to see what happened…


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