Small extension on a prefab garage?

[Harry Bloomfield]

Hi,

I'm looking at ways to extend a pre-fabricated garage which has a corrugated cement asbestos roof, or rather ways to sort out rain water flow from the roof...

Slope of the roof is from front to back with water presently running into a gutter at the back and it is the rear to which I would like to build a small block work extension integrated into the garage.

Due to rising slope of the ground at the rear, the new extensions floor level would be stepped up from the main garage slab level - basically this would mean the extensions roof would have to be a little higher than the rear edge of the garage. Idea is to remove rear windows of garage, plus 3x short concrete panels below windows which would then allow through access in to the extension. Continueing the slope of the garage roof down over the extension, is not possible as the height at the rear would then not be adequate.

I'm looking for ways to have both roofs form a shallow V draining at the joint between the original and new extension.

So how do I achieve drainage of the roof? Probably some sort of built in gutter leading to the side?

Anyone done anything similar?

[Chris Bacon]

That's called a "secret gutter", which you could make nice and expensively with lead-lined timber (say 6" bottom, 4" sides), or less expensively with GRP (fibre glass). It would be better to replace the whole roof, though, with one continuous one, of

4x2 & 2x2 with galvanized iron sheeting underlayed by 11mm Sterling Board.

[Harry Bloomfield]

Chris Bacon used his keyboard to write :

That sounds good, would easily fit in the space and provides me with some words to conduct a search upon.... Thanks.