Towering Inferno

Ever wonder why flat roofs, especially on older buildings, often have pebbles on them?  Decoration? Drainage? Or something very “now” that the original builders probably didn’t even think about?

QUESTION: I own a unit in a seventies style solid brick complex with concrete slab roofs. My unit is on the ground level and is more or less free standing, there are two other low-rise buildings attached.

When I bought the unit, it was reasonably cool, rarely needing air conditioning even in summer. Two years ago the roof’s waterproof membrane needed to be replaced but when the work was completed the layer of pebbles completely covering the roof area wasn’t replaced.

I now live in a hot box.  By 3pm on a sunny day, the concrete ceiling becomes hot to the touch and the temperature underneath is about 40 degrees. This does not subside until the early hours of the morning. Without two air conditioners going flat out, the unit would be inhabitable. Even with the air con going you can feel the heat from the ceiling.

I have reported it to members of the Executive committee, but they just say “get used to it – all residents on the top floors have the same problem.”  What should I do? It could be hard for me to either resell or tenant it as is. – HotBox, Cremorne.

ANSWER: The pebbles were probably put on the roof mainly as ballast to hold the previous membrane down but they also had a secondary role as a “heat sink”  to providing passive cooling.

Their removal has therefore not only introduced a defect into the block but has made your apartment complex much less “green”, with all those air-cons going full pelt.

Your owners corporation has a legal obligation to maintain the building and fix defects – they have allowed a level of insulation to be removed –  and I would give them one final chance to do the right thing before you take them to Fair Trading (Tel. 13 32 20).

You could be doing them a favour – a few hundred dollars spent on pebbles could save thousands on electricity bills over the years.

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