Bolted wrote:

I currently have an awful kitchen extension with a monopitched roof,
that was built by the cowboys from hell and has no redeeming features at
all. It has to go. If I have to replace it, I'd like it to be bigger,
as it is currently a 6m wide by 2.8m deep (i.e. towards garden) galley
kitchen which doesn't really suit a quite big semi.

The neighbouring semi has a flat roofed extension, but I would very much
like to avoid this from a practical perspective as well as aesthetic.
The difficulty is that to extend the depth of the kitchen further into
what is now the garden means that the current monopitch roof can't be
replicated, as there is insufficient height under the first floor
window. There would be enough height for a pitched roof with the gable
end pointing out towards the garden and the slopes heading down toward
the side of the house (on the detached side) and the next-door flat roof
extension on the other side.

My question is, is the a usual way of dealing with this situation? The
slope that abuts the neighbour's wall will need a draining htvalley at
rig angles to the main slope, so that the water flows down toward the
garden. Can anyone help with how is this done, because I am finding it
hard to envisage?

I recently had an extension built from scratch and the architect said
that to have a mono-pitched roof (using tiles which matched the existing
tiles - my spec.) needed a layer of 'onduline sheeting' (a corrugated
plastic sheet) between the rafters and the tiles as otherwise rain could
blow under the tiles as the pitch of the roof was less than specified
for the design of (common Redland) concrete tiles. IIRC the structure of
the roof is (attempt at ASCIIart)

/\/\/\/\/\/\/\/\/\/\ Tiles
--------------------- battens across the roof
^^^^^^^^^^^^^^^^^^^^^ onduline sheet
--------------------- battens across roof and felt

HTH

Malcolm

PS so far in 9 months it ts waterproof