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)

[george]

On Sat, 9 Jul 2016 06:28:53 -0700 (PDT), DICEGEORGE
wrote:

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)

[george]

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.

AB

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

DICEGEORGE wrote:
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)

A hole in a flat roof? - you can't just invent new ways of building things,
there are set ways of building a flat roof....who told you to do it like
that?

FWIW, if the drain hole ices up, the snow won't melt.

Snow has never brought down a roof in this country - snow weighs a tenth of
water, so you'd need 10ft of snow for it to equate to a foot deep of water

On Saturday, 9 July 2016 14:46:35 UTC+1, Phil L wrote:
DICEGEORGE wrote:

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?

The roof must be able to support the snow.

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

water goes upward?

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)

No-one does that because it's a prodigious waste of energy & money

A hole in a flat roof? - you can't just invent new ways of building things,
there are set ways of building a flat roof....who told you to do it like
that?

There are lots of old flat roofs done that way.

FWIW, if the drain hole ices up, the snow won't melt.

Snow has never brought down a roof in this country - snow weighs a tenth of
water, so you'd need 10ft of snow for it to equate to a foot deep of water

That might be true for residential, but certainly not for other types of roof. Snow is heavy stuff, 6mx6mx0.3m = 10.8 cubic metres. Water weighs a tonne a cubic metre - what snow weighs depends on its density, which is quite variable.


NT

On 09/07/2016 14:28, DICEGEORGE wrote:
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


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.

--
Robin
reply-to address is (intended to be) valid

On 09/07/2016 14:48, Phil L wrote:
Snow has never brought down a roof in this country - snow weighs a tenth of
water, so you'd need 10ft of snow for it to equate to a foot deep of water

Have you ever had a foot of water on your roof?

This is not a residential property, but it is a UK roof:

http://www.telegraph.co.uk/news/weat...t-of-snow.html

http://www.fwi.co.uk/business/roofs-...n-scotland.htm

--
Rod

On Sat, 09 Jul 2016 06:28:53 -0700, DICEGEORGE wrote:

I'm building 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 under 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)

[george]

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.


Cheers


Dave R



--
Windows 8.1 on PCSpecialist box

On Saturday, 9 July 2016 14:28:56 UTC+1, DICEGEORGE wrote:
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)

[george]

All roofs in the UK are designed with a snow load in mind.
Even the sloping ones.
It's a distributed load so not as great problem as you might think.

On Saturday, 9 July 2016 15:09:29 UTC+1, Robin wrote:
On 09/07/2016 14:28, DICEGEORGE wrote:
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


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.

--
Robin
reply-to address is (intended to be) valid

You can use any slates.
The roof has to have sealed or upstanding joints.
There are many different systems.

Flat roof BTW are never flat, there is a slight slope for drainage.

On Saturday, 9 July 2016 16:40:55 UTC+1, harry wrote:
On Saturday, 9 July 2016 15:09:29 UTC+1, Robin wrote:
On 09/07/2016 14:28, DICEGEORGE wrote:
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


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.

--
Robin
reply-to address is (intended to be) valid

You can use any slates.
The roof has to have sealed or upstanding joints.
There are many different systems.

Flat roof BTW are never flat, there is a slight slope for drainage.

Sorry that should read "can't" use any slates.

On 09/07/16 14:28, DICEGEORGE wrote:
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)

[george]


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.

In article ,
wrote:
On Saturday, 9 July 2016 14:46:35 UTC+1, Phil L wrote:
DICEGEORGE wrote:

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?

The roof must be able to support the snow.

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

water goes upward?

with the wind in the right (or wrong) direction is does here/

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)

No-one does that because it's a prodigious waste of energy & money

A hole in a flat roof? - you can't just invent new ways of building
things, there are set ways of building a flat roof....who told you to
do it like that?

The flat roof here (and in my last house, has a drain hole.

--
from KT24 in Surrey, England

On 09/07/2016 14:28, DICEGEORGE wrote:
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)

[george]

Of course, if you didn't have that Kingspan in there, heat loss from the
house might have melted the snow.

--
Rod

thanks for advice,
photo is at
http://www.stonehengecampaign.org.uk...f-north01s.jpg
and
http://www.stonehengecampaign.org.uk...rtheast01s.jpg

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...

[george]




On Saturday, July 9, 2016 at 2:28:56 PM UTC+1, DICEGEORGE wrote:
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)

[george]

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

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"DICEGEORGE" wrote in message
...
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)

[george]

"Archibald Tarquin Blenkinsopp" wrote
in message ...
On Sat, 9 Jul 2016 06:28:53 -0700 (PDT), DICEGEORGE
wrote:

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)

[george]

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.

A bit overkill? Whats wrong with 230V and a 30mA RCD?



--
Adam

DICEGEORGE wrote:
thanks for advice,
photo is at
http://www.stonehengecampaign.org.uk...f-north01s.jpg
and
http://www.stonehengecampaign.org.uk...rtheast01s.jpg

the drain hole is in the wall
under the orange rope on the right

That wall doesn't need to be there, at least the top part of it doesn't need
to be there, why are you knocking a hole out when the wall could be taken
down to roof level and then it can't block up.

(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...

The worse case scenario is that the BCO is coming on Monday....he's not
going to accept this.

On 09/07/2016 22:59, DICEGEORGE wrote:
thanks for advice,
photo is at
http://www.stonehengecampaign.org.uk...f-north01s.jpg
and
http://www.stonehengecampaign.org.uk...rtheast01s.jpg


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.

--
Robin
reply-to address is (intended to be) valid

Robin wrote:
On 09/07/2016 22:59, DICEGEORGE wrote:
thanks for advice,
photo is at
http://www.stonehengecampaign.org.uk...f-north01s.jpg
and
http://www.stonehengecampaign.org.uk...rtheast01s.jpg


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.

No matter how many times I look at this, and all the other photos that he
has uploaded, I can't see any flat rooves anywhere - this picture shows two
pitched rooves coming together into a valley

[ 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


[ 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...

[george]

On Sat, 09 Jul 2016 06:28:53 -0700, DICEGEORGE wrote:

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?

I'd be more worried about the drain hole getting blocked with leaves etc,
tbh.

On 10/07/2016 16:03, DICEGEORGE wrote:
[ 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


I'd have thought an off-the-peg heated roof outlet would be the first
step if you are that worried.

And that taking the the membrane further up under the slates would be a
cheaper than any form of general heating.
--
Robin
reply-to address is (intended to be) valid

" off-the-peg heated roof outlet "
sounds interesting ..
but google doesnt find anything relevant...

DICEGEORGE wrote:

"off-the-peg heated roof outlet"
sounds interesting .. but google doesnt find anything relevant...

"optional heating element"

http://www.alumascroofing.co.uk/products/roof-accessories/flat-roof-outlets/harmer-insulated-roof-outlets

On 10/07/2016 19:48, DICEGEORGE wrote:
" off-the-peg heated roof outlet "
sounds interesting ..
but google doesnt find anything relevant...


Google is not the only search engine, and yours are not the only search
terms In addition to Adrian's link a minute or 2 on Bing gives


http://www.guttercentre.co.uk/Harmer...FTUz0wodK5UPAA

http://www.guttercentre.co.uk/Harmer...let-Heated-1-1

http://www.topwet.co.uk/products/134...bitumen-sleeve

https://www.fruugo.co.uk/roof-roofin...FRSeGwodvfkMzA


NB I've not used them. I know of them only from an aborted house
purchase 3+a bit years ago.

--
Robin
reply-to address is (intended to be) valid

On 10/07/2016 20:37, Robin wrote:

terms In addition to Adrian's link a minute or 2 on Bing gives


Adrian? Sorry Andy. Put it down to the way front-of-the alphabet names
tend all to look alike to this victim of alphabetism ;(


--
Robin
reply-to address is (intended to be) valid

Robin wrote:

Adrian? Sorry Andy. Put it down to the way front-of-the alphabet names
tend all to look alike to this victim of alphabetism ;(

And we're always the ones that get butt-dialled :-(

On Sun, 10 Jul 2016 21:01:51 +0100, Robin wrote:

On 10/07/2016 20:37, Robin wrote:
terms In addition to Adrian's link a minute or 2 on Bing gives

Adrian? Sorry Andy. Put it down to the way front-of-the alphabet names
tend all to look alike to this victim of alphabetism ;(

No problem, Ursula. I shall try not to be too mortally offended...

On Saturday, July 9, 2016 at 2:28:56 PM UTC+1, DICEGEORGE wrote:
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?

xxxx

Permaroof, who make the EDPM I'm going to use sell this:
http://www.permaroofstore.co.uk/prod...araphet-outlet
EPDM Through Wall/Paraphet Outlet,

But as Andrew says I'm now worried about it getting clogged with leaves,
so better to use the full width of the hole in the wall
with some sort of overhang and hopper on the outside.

But if I use wood for the overhang i'm worried it will rot over the decades,
and if I use metal i'm worried it will conduct coldness and increase ice build up...
so some sort of plastic base for the EDPM and overhang?

I'm off to a one day course at permaroof tomorrow


george

On 11/07/16 13:21, DICEGEORGE wrote:
On Saturday, July 9, 2016 at 2:28:56 PM UTC+1, DICEGEORGE wrote:
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?

xxxx

Permaroof, who make the EDPM I'm going to use sell this:
http://www.permaroofstore.co.uk/prod...araphet-outlet
EPDM Through Wall/Paraphet Outlet,

But as Andrew says I'm now worried about it getting clogged with leaves,
so better to use the full width of the hole in the wall
with some sort of overhang and hopper on the outside.

But if I use wood for the overhang i'm worried it will rot over the decades,
and if I use metal i'm worried it will conduct coldness and increase ice build up...
so some sort of plastic base for the EDPM and overhang?

I'm off to a one day course at permaroof tomorrow


george


Use metal - it will make no practical difference. If it's that cold,
stuff will freeze anyway and vice versa.

tim wrote:
[Use metal (under the EDPM at the outlet) - it will make no practical difference. If it's that cold, stuff will freeze anyway and vice versa. ]

hm.. and if the air temperature gets above zero then the metal will pick this up and transfer it to the ice quicker and melt it quicker ... if my physics is correct ...

[g]

On Sat, 09 Jul 2016 14:59:37 -0700, DICEGEORGE wrote:

thanks for advice,
photo is at
http://www.stonehengecampaign.org.uk...ntralflatroof-
north01s.jpg
and
http://www.stonehengecampaign.org.uk...ntralflatroof-
northeast01s.jpg

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...

[george]




On Saturday, July 9, 2016 at 2:28:56 PM UTC+1, DICEGEORGE wrote:
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)

[george]

Interesting pictures which explain much but still raise a couple of
questions.

That shed door thingie to the right of the picture - is it a shed door or
your access to the roof? I assume the area to the right of the picture is
your area of concern for flooding, not the roof to the left which is
covered in plastic sheeting?

The brick wall in the centre looks new (or at least recently fettled). Is
this the cause of your concern about drainage?


Any chance of a picture facing to the right, with that little door in the
left of the picture, showing what is there opposite the new low pitch roof
you are constructing? This is just me being very nosey because the whole
set up looks fascinating.

Cheers


Dave R



--
Windows 8.1 on PCSpecialist box