Use of lead for hidden gutter, maximum length

[Rodge]

I'm exploring the use of lead to construct in-board/hidden guttering on my small single-storey self-build, quasi Passive.  No eaves.  I'm wonderng whether anyone has experience of using lead contrary to the specifications of (e.g.) Calder and Associated Lead.  These specify a maximum run of 1500mm (most frequently) for a single sheet of lead.  But I am thinking of running it for 4000mm strips, simply U-shaped and fixed only at one end to allow for expansion movement.  No horizontal joins given challenges in lead  Is this foolish?

 

BACKGROUND: The gutter will run along the side of the building, with the water flow running from the upper level, down a 1.1m slope at 31 degrees, to the lower level.  The image hopefully gives an idea of situation, and shows the temporary gutter sitting outside the face of the insulation, in a relatively conventional way - just to keep the water off this side to which the slightly-sloping roof drains.  This was a trial and my 'eye' doesn't like the look of it on a modern style house.  When the roof insulation is installed, the plan is to leave the second layer insulation board 100mm short of the edge, and to 'simply' rest the gutter on that ledge, suitably secured.

 

A major attraction of using lead is the ease with which I could (I think)  join the horizontal lead to the 31 degree slope (with a slight bend downward, directing water down the slope) and to fashion an outlet that directs the water horizontally to the downpipe (with an appropriate step down from the horizontal gutter - although the standard 50mm drop down would be require a larger-than-desirable cut down into the insulation.)

 

Grateful for any thoughts.

Rodge

 

[Tom]

Just get a steel gutter fabricated? It's what I did for the hidden gutter for our Nudura build.

 

https://www.panelsandprofiles.co.uk/industrial/galvanised-steel-guttering/

[Russell griffiths]

You will get such massive expansion and contraction at that length it will crease and fracture. 

[Adsibob]

Our concealed gutter is powder coated aluminium U shaped channel. 4.2m long from memory, not had any issues.

[Rodge]

Russell Griffiths,

Thanks for the responses.  Re expansion, have I calculated wrongly? - must have done if that is the experience.  Doing the calculations with the Coefficient of Linear Expansion of lead and for a 25 degree temperature change gives an expansion of 1.1mm over 1500mm, and 4.4mm over 6000.  With the lead only attached at one end, quite narrow (300mm or so) and free to move over its length, I was assuming that the expansion wouldn't be problematic.

 

Rodge

[Mr Punter]

Unless you have a skilled leadworker on side you would be better with ali, grp, zinc or steel

[Russell griffiths]

I was just going by the Calder lead guide 

I’ve always stuck to the 1.5m

i see your only fixing it at one end, so I think your in unknown territory. 

[Rodge]

Thanks for the thoughts.  I'll have a look at the panels and profiles offering, but may well turn to the aluminium route, perhaps with lead to create the specialist joins.

 

Very helpful, Rodge