Roof Top Grass

[newton]

I have seen sedums used instead of grass for rooftops and it looks really good plus it handles the heat and dry weather a lot better, requires little soil and maintenance. here is a step by step link for an installation on a building in Germany, it would be interesting if somebody could replicate it with equivalent in Pakistan, im sure the added greenery would have a cooling effect for the rooms underneath. A little bit like the thermal efficiencies of our old mud roofs.

http://localecologist.blogspot.co.uk/20 ... t-594.html

some places in the world actually use just this in place of tiles or slates or concrete etc

[Hamad]

yes, you are right I have seen people growing them on the roof in UK and they do require very thin layer of growing medium, I have tried couple of varieties in Pakistan but its hard to keep them round the year as when they grow, they grow crazy but all of sudden they get vanished or I may don't know the way to keep them for longer (any experienced member who is growing them? for a tip), they are good to keep the house cool but actually I was looking for a grass that can be grown on Terrace or Roof top any idea?

Hamad

[newton]

The problem that exists with growing basic grasses on roofs is that the building structure has to be constructed to be able to cope with the extra weight and permeability of both damp and roots.

On average if you require to grow traditional lawn grass on a roof then you can expect around 56kilo of extra weight per square foot. So for a 20ft x 30ft area that equates to 56 x 600 = 33.600 kilo or 33.5 metric tonnes. calculations are approximate and include the soil, substrate and moisture/water content.

Growing things like sedums, mosses and herbs the loading charachteristics are much less at 8kilo per square foot or 8x600= 4,800 or 4.8tonne

Clearly both types have to be carefully constructed with loading calculations included at the build stage otherwise problems will occur and in fact it could be quite foolhardy and dangerous to do so otherwise.

The ancient methods of house construction with gharra walls, mud roofs and mud/mitthee plastering incorporated substantial beams and thicker walls are probably best for green roofs if proper waterproof membrane is included. generally only single storey though, however as we all know this practise has been mostly discontinued and in most places now non-existent.

It is a shame though as it was adapted over thousands of years to be the most cost effective, thermally efficient, earthquake and insect attack proof, Ideal for our climate. Green lawn roofs on such structures would be ideal and the load could be taken, some of our older readers may remember though the dangers of living in these houses during the monsoon rains as some poorly built ones would collapse under the extra water weight. By contrast most houses in Pakistan these days are built where they are far too hot in the summer and far too cold in the winter, taking enormous amounts of energy and cleaning to reduce the flies and mosquitos which are more attracted to the inevitably lived in sticky painted walls and marble floors.

In my humble opinion modern houses would be unable to take the extra weight of a green roof neither would they be conducive to a good growing environment as the plants roots would cook/heatup during the day, the concrete and steel very efficiently radiates the heat when watered the thermal shock of sudden coolings inevitably kills plants off.

I know this information and the loadings as only last month I was talking to a professional installer of green roofs in the UK and I asked him the very same question.

[Hamad]

Newton very nicely summed up and concluded and I do agree with you

thanks

Hamad