Thin screed and underfloor heating?

I have an existing narrow solid floor hallway, about 3.6 x 0.8 m. The concrete floor has about 4-5 mm screed (concrete base is very rocky so depth is variable), the house is old and sothere is no sub-floor insulation.
Do I have any realistic options for getting in underfloor heating - without raising the floor level or digging up concrete (I might just be able to bear digging up the screed - again)?. Would prefer wet UFL but would think about electric - but not on uninsulated floor (to be tiled).
As far as I can see I'm snookered unless I can cram adequate insulation plus a screed plus UFL plus ceramic tiles into about 40 mm.
The alternative would be very thin wall radiators - if such things exist!.
Paul
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You can get skirting radiators. They are thicker than skirting boards and don't look as nice, though.
Christian.
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I have a single panel radiator in smaller space than yours. Total distance from wall to "outer" edge of rad is 75mm.
That would not eat up much of your 800mm. I have much less width than that, and still have room to pass.
In my understanding (as a prospective buyer, not an expert), 40mm is not enough to for a proper installation of underfloor heating.
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I've found that, according to the below site, some insulation boards ('Marmox' - there may be others) can be used over, or instead of, screed rather than under it. You can then lay electric UFH and tile over that. Comes in various thickness from 10mm, I'd need to check out it's fire-resistant qualities though.
As the passage takes a lot of thru traffic, including bikes, I'm keen to avoid radiators or any wall-mounted heaters that would obstruct and get knocked over time if possible.
Wet UFH still looks difficult, 40mm (4-5mm in OP was a typo!) doesn't seem enough to play with...
Paul.
http://www.floorheatingsystems.com/insulation/marmox/marmox.htm

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40mm is on the edge, 50mm is OK as long as you use fibre reinforced screed.
You could proabaly get away with 40mm if you used a 100mm square steel mesh about 10mm or so up from base of screed and used a fibre reinforced screed.
Rick

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Or possibly this:
http://www.heatprofile.co.uk /
?
It's a skirting board radiator (but not like the nasty ones you used to have in school) and is 140mm high by just 25mm deep. You might need a fair length of it (180 W/m at 80C) but it should be easier than UFH...
Just a thought.
Hwyl!
M.
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