The Spain Forums

The Sat and PC Guy

Personally i would not drill into a roof.
A roof with holes drilled into it is not a roof when it rains.
Especially with holes the size required for the bolts that i would use (16mm)
And with some of the rain we get in Spain.
Any installer should know that!!!
They must be real stupid if they have done that, as even with silicone water can get in.

Some of the strength of the concrete comes in its ability to stick to the surface, so a plastic sheet would not help. it may also make the base slide should water get to the sheet - the water with plastic acting as a lubricant.

Anyways, for a 1.8m dish i do a minimum 80cmx80mx25cm concrete base, for 2.4 is do a minimum of 1mx1mx25cm. i have some very strong wood cut to size and clamp it together to form the square. see here for an image of how not to do it with bolts and yeso, and then how to do it - http://www.satandpcguy.com/Site/Dishes.htm. i do have some pix - will be on the site soon - of a base done with dry concrete mix (so the base and dish can be done in a single day) that was done about a year ago and that you can push your finger into now it has cracked so much - the dish rocks in the wind and it base cracks even more....

I dont like to use bricks or blocks as the shuttering, as i have found that when other installers have used this method, when there is a string wind, the dish and the concrete in the centre comes loose and flies away, leaving the blocks intact as the concrete has not really attached itself to these blocks - wish i had my camera last time i say this happen - the dish and half of the concret was tetering on the edge of the appartment blocks roof.

Make the shuttering around the base and just pour the concrete in - some rebar may also help...plenty of it lying aorund...

you (or at least i) can get a bag of mixed sand and aggregate. i use a mix of 4 to 1. if done correctly you should use about 10 bags of sand aggregate mix.

Hope this helps....

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peregrine

Thanks very much, Jon, for that comprehensive reply...I guess it's a little too late for me now, as the holes have been drilled....I have also added my own silicone around the base of the metal support, and over the bolt heads...but I do know that water will always find its way to where it's not wanted...maybe though, I will be lucky, as the dish is not over exposed, there being a 3 foot wall keeping the wind off most of it...I may well now, though, cover the base in concrete, to the dimensions you state...thanks again.
Just to add that the installer has said, in defence of the bolted system, that he has had no failures in the years he's been using the method...I do, however, see that your system is easily the most preferable, and, dare I say, professional? And, being a cynic by nature, it's obviously so much easier to install a system base with bolts rather than the time-intensive correct way!
Thanks again...I'll try and dream up some more queries