I'm bulding a flat roof, with a hole for water to drain out of but what if lots of snow collects on there and the drain hole ices up?
At the least melting snow could find its way up udner the slates and into the house,at the worst the weight of snow could collapse the roof
Could I install some kind of electric heater under it (and on top of the kingspan), how and what would this be (obviously dont want to get hot and burn it down)
Yes I'm sure you could. Flat trace heating cable and a control thermostat would allow you to fit & forget. If I were going down that route though I think I'd probably go 110V center tapped.
I'm not sure I understand your design, it sounds a little odd. I would have thought a conventional gutter under the lowest side would be fairly immune from drainage problems.
If you do not have a good slope to wherever you are draining, you will end up with pooling and with most coverings this means trouble.
Just for my education, what slates can you use on a flat roof? I thought BS 5534 pointed to 20+ degrees and that 15 degrees was the limit even in unexposed areas.
Could you please supply a bit more detail about the roof design, slope (if any) and materials? Also where it is attached to the house?
The obvious answer is to design the roof so that it can support the expected maximum weight of snow.
You also can't make any assumptions about the snow melting, because if the area where you live has cold winters and a high snowfall (I assume it must because you are asking the question) then the scenario you must design for is the snow falling and not melting. Perhaps the snow could sit on the roof for a month or more. Topped up by additional snow fall.
An alternative would be to design the roof so you can walk on it, and then just get up there with a broom and sweep the snow off.
I assume that your concern over the slates is that snow could build up high enough on the flat roof to cover the lowest slates on the adjacent sloping roof? Or does your house have a vertical wall faced with slates?
At first read your concerns seem a little unrealistic so more context is needed.
You design your roof for the snow loading in your part of the UK.
An active solution would be unwise as a heavy winter is when your electricity supply is most likely to fail. The passive solution is to make the roof strong enough for the worst case weight of snow and ice.
the drain hole is in the wall under the orange rope on the right
(not sure exactly how i'm going to do it but this is the time to think about melting ice if itblocks up
We havent had a lot of snow here since maybe 1963 butif climate change changes the gulf stream we may get lots of snow as we're surrounded by sea and quite north.
Building Control are coming on Monday I'm worrying about worst case scenario...
Sounds like a bit of a waste of energy to me. I don't believe this idea is going to work in any case. The snow can semi melt and still clog things up. Where I used to work they had a heated roof car park ramp to stop people getting stuck. Did not work due to uneven heating and it still froze at night. Brian
Are you going to take the covering on the flat roof up under the slates so it's at least 6 inches above the flat bit? If so I don't see how water can get into the house under the slates unless the roof turns into a tank holding water deeper than that.
re: [ I don't see how water can get into the house under the slates unless the roof turns into a tank holding water deeper than that. .] yes, thats what i was worrying about if it fills with snow and ice
re: [ I can't see any flat rooves anywhere - this picture shows two pitched rooves coming together into a valley ]
there used to be 2 valleys and a smaller pitched roof in the middle, now I'm building what i call a flat roof covered with EDPM about 4 meters by 4 meters which you could also call a valley
I think I'm worrying too much, lets see what the Building Control man says tomorrow...
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