On 21/05/2016 08:49, Andy Burns wrote:
Tim Lamb wrote:

Andy Burns writes:

With all them 'oles in the metal web, why would you even want to cut
slots?

Wet underfloor heating (Speedfit) uses aluminium spreader plates nailed
to the joist tops with the pipe run trapped in pre-formed channels. The
pipe has to go through or over the joist to reach the next joist pair.
Going through involves a lot of pipe threading.....

OK, I see. JG seem to recommend fixing the plates to the bottom of the
flooring when using engineered joists rather than to the top of the
joists ...

https://www.youtube.com/watch?v=gx2jEz3bfkk

The OP wrote "... to return the underfloor heating pipes" - I did not
take that to mean the loops at the end of every joist.

Nevertheless, I cannot see any significant reason other than reducing
the threading of the pipe to cut slots rather than holes in the web.
And, if the layout is very simple, you could pull the pipe through all
the webs at one end, then pull more and more pipe through to form the
loops. Wouldn't seem to be that much of a problem.

--
Rod