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**Khcyhshq** · 07-06-2012, 07:25 PM

How thick is your gravel layer Pichardo? If too thick you might have loads issues on your roof, no?

Barnabé

At fist we used the cheap and big chunks type of gravel, not white nor was it light. The layer came about 3 inches + thick with that one and the roof was Ok with the added load.

After learning from trial and errors (three times, three different types of gravel material/pebble sizes), I found that the small sized whitest pebbles did the best job of all. The end layer was about no more than 2 1/2 inches thick at the bumps and averaged some 1 1/2 around the whole area. The cooling factor was increased by a factor of 3 and the dampness retained during the heat waves after intentional sprinklings was excellent.

It took me a while to get the correct material/sized gravilla.

The load is spread on the roof, so the added weight is of little issue to 99% of concrete slabs, unless you have plenty of air pockets in yours due to poor mixture, high alkali and cut corners during the construction process.

Somebody (with a commercial structure using the same application) told me to do like him, and use a sprinkler system atop the roof to keep the gravel damp automatically during the hottest waves. He modified the timer for the sprinklers with a mercury cut off/on switch that allows the system to activate when needed using rain water collected in several tanks on the down spouts. I checked the thing up, but I find that the investment pays off for a large scale thing like his, not a mere home roof like our property. Plus I liked to go atop the roof and wet it using garden house (It feels kind of therapeutic).

07-06-2012, 07:25 PM	#28
Khcyhshq Join Date Oct 2005 Posts 403 Senior Member	How thick is your gravel layer Pichardo? If too thick you might have loads issues on your roof, no? Barnabé At fist we used the cheap and big chunks type of gravel, not white nor was it light. The layer came about 3 inches + thick with that one and the roof was Ok with the added load. After learning from trial and errors (three times, three different types of gravel material/pebble sizes), I found that the small sized whitest pebbles did the best job of all. The end layer was about no more than 2 1/2 inches thick at the bumps and averaged some 1 1/2 around the whole area. The cooling factor was increased by a factor of 3 and the dampness retained during the heat waves after intentional sprinklings was excellent. It took me a while to get the correct material/sized gravilla. The load is spread on the roof, so the added weight is of little issue to 99% of concrete slabs, unless you have plenty of air pockets in yours due to poor mixture, high alkali and cut corners during the construction process. Somebody (with a commercial structure using the same application) told me to do like him, and use a sprinkler system atop the roof to keep the gravel damp automatically during the hottest waves. He modified the timer for the sprinklers with a mercury cut off/on switch that allows the system to activate when needed using rain water collected in several tanks on the down spouts. I checked the thing up, but I find that the investment pays off for a large scale thing like his, not a mere home roof like our property. Plus I liked to go atop the roof and wet it using garden house (It feels kind of therapeutic).
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