Building Construction, Renovation, Maintenance & Advice

Repairing Water Leaks in Concrete Roofs

"Drips Anonymous"

Water is sneaky stuff.

Don’t get me wrong, I have nothing against water, in fact I quite like it. But it is sneaky.

We would be a bit stuffed without water wouldn’t we? For I start we would all be a bit smaller, about 90% smaller in fact. We’d be a bit dirty as well without a shower every now and then and we would certainly have dry mouths. No cups of coffee to start the day, there would be a few dive operators out of work and the beach would be rather boring. Worse the underarm deodorant industry would struggle to survive.

So why is it sneaky? Well it has a way of finding every tiny hole and crack and getting to places we don’t want it.

Eric knows about water. He had a bit of a problem. He is a graphic artist with rather a nice studio at his house.

He called me one day. “Help” he said ”I’ve got water coming out of my light fittings and dripping on my work benches!” He went on to say that one light fitting had set on fire.

What a mess! Above his benches were a series of lights fixed into a concrete ceiling. Water was dripping from most of them. In one corner black smoke marks trailed across the ceiling from a melted blob of plastic. Rather frightening.

Eric’s concrete roof was flat. (Now why was it that our ancestors in their wisdom decided that roofs should be sloping, was it so they looked pretty? – I forget but I do know that the sloping roof was the third great invention after the wheel and the bottle opener).

Eric’s roof was leaking.

He called a Tukang, a man from Java who came to fix it.

Our Javanese waterpoofing “expert” decided to put a layer of cement on top of the roof. It cracked and the roof still leaked.

He then decided to put a corrugated plastic roof on top of the concrete. It was too flat, water got under it and it didn’t work.

Finally he put corrugated asbestos on top of the plastic which broke, flattened the plastic and made things even worse.

Now Eric had been a good looking man with a fine head of dark wavy hair (it’s true, he showed me the pictures), well he was till his roof started leaking. As attempt after attempt failed he steadily became a shadow of his former self. He aged, his eyes stared vacantly and his fine head of hair was gone, torn out in desperate frustration. He twitched and mumbled incoherently about the days of his youth when roofs were sloping and didn’t leak.

Sneaky stuff that water.

We all know that it likes to go downhill and find the lowest place it can but it also likes to get blown sideways by strong winds and, even worse, believe it or not it likes to go uphill if it can find a narrow crack or something porous through that strange phenomenon capillary action.

Capillary action is the really sneaky bit that allows water to climb from the ground up your living room walls. These days houses in many countries have a damp proof course to stop the water rising. But water is very clever and a damp proof course must be well designed and properly installed if it is going to work. But more of this another time.

Eric’s roof had only one small drain and overhanging branches dropped leaves and blocked it frequently leaving a nice place for mosquitoes to breed. The concrete roof looked like it had been put in place by a drunken baker who couldn’t find his rolling pin. Worse, it had holes drilled through it to put the wiring through. Not a good idea on a flat roof. Capillary action was sucking the water from the roof and into cracks and wiring ducts.

Waterproofing is a surprisingly difficult skill. Simply squirting a bit of silicone into any orifice you can find might stop a noisy dog from barking but fixing a leaky flat concrete roof requires far more subtlety. Also, as our muddy friends in Java have found out, it is also not very effective trying to block where it is coming out - it is important to find out where and how water is getting in in the first place. Finally it is important to get the right materials and have them properly applied.

Eric is a happier man now. His hair is growing back and the eyes don’t stare as much. He has been attending a self help program called “Drips Anonymous” where leaky roof victims meet to support each other. He is getting better each day and if all goes well he may soon be able to face a glass of water again without going into spasms.

Copyright © Phil Wilson 2009
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17 July 2017 Copyright © Mr Fixit,
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