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.
It may be of interest to HotBox, Cremorne that there is provision in the NSW Strata Management Act to dampen Owners Corporations ability to make changes to common property.
Chapter 3, Part 2, Clause 65A Owners corporation may make or authorise changes to common property
(1) For the purpose of improving or enhancing the common property, an owners corporation or an owner of a lot may take any of the following action, but only if a special resolution has first been passed at a general meeting of the owners corporation that specifically authorises the taking of the particular action proposed:
(a) add to the common property,
(b) alter the common property,
(c) erect a new structure on the common property.
In the Act, “a special resolution means a resolution which is passed at a duly convened general meeting of an owners corporation and against which not more than one-quarter in value, ascertained in accordance with clause 18 (2) and (3) of Part 2 of Schedule 2, of votes is cast.”
—IngridSo if may be that HotBox has a strong case, if the change to the roof was not approved by a special resolution at a General Meeting of owners.
Hi Hotbox
—Dominic OgburnAs a building consultant I come across your very issue quite often. If the roof membrane is a dark coloured sheet membrane then one of the most effective ways of reducing solar heat gain is to paint the membrane with say a white coloured quality acrylic paint. I think you’ll find that this will be cheaper and easier than the pebble solution and should provide significant relief. The pebbles were intially installed to also make the membrane trafficable for the purpose of maintenance and to limit damage. If the new membrane does not incorporate such ‘protection’ it may not be fit for purpose.
Regards
Dominic
I feel for Hotbox: that roof is acting like an absorbent solar panel and it sounds as though the EC is incompetent, at least to the extent that they have obviously not taken independent advice.
—Philip AtkinThe best answer to the problem is to install interlocking polystyrene boards (specially made for this purpose) over the new membrane, then add the layer of pebbles. The cost of the insulation and pebbles will be good economics because, as well as keeping Hotbox cooler in summer and warmer in winter, the life of the membrane will be extended significantly. Both the insulation and the pebble layer should each be at least 50 mm thick. Alternatively, if pavers were laid over the insulation layer the roof could be used as a deck.
Telling Hotbox to like it or lump it is short-sighted in the extreme: as well as Fair Trading, the local council may be able to contribute to pressure on the EC to do the right thing.
Good luck!
Philip Atkin