On 28 Mar, 16:29, JimK wrote:

Andy - from a quick google on here I believe you recently did one?
using perlite/vermiculite etc - care to share?

My small workshop roof is 8' x 24' and began as flat corrugated iron.
The green roof was to make it look nicer, fix its obvious plan to fall
down imminently, and to get some insulation in there. It's now almost
flat, with 3" of soil over 1" of vermiculite, over 1" of polystyrene
insulation.

Construction began by discarding the old roof and the top foot of
wall, owing to original poor construction. A course of cement blocks
and a course of bricks on one long wall, tapered at the end walls.
Joists were 4"x2" on 400mm spacings, laid on top of this new wall and
held up by noggins between at the ends. They stopped an inch short of
the outer wall edge. Roof deck on top of this was 3/4" OSB screwed
down - fortunately my shed is a convenient 6-sheet multiple, so
everything fell out of standard lengths quite nicely, helping with the
budget. A surrounding upstand wall of 3/4" OSB was made, screwed into
the edge of the OSB, with long screws through the foam (see below) and
into the noggins, then against the outer masonry edge - no overhanging
eaves. The entire external woodwork was then coated with black bitumen
paint (runny stuff - real fibre-reinforced exterior grade is
impractical to apply over OSB) . 1" of polystyrene foam went down on
top, to make an insulated warm roof. This same foam was used around
the edges of the joist, between the noggins and the upstand wall to
avoid a cold bridge there.

Around this time, I still needed a ladder to the roof, but no longer
needed to move the ladder around as I worked. So I rawlbolted the wall
and tied my strongest and steadiest ladder down to it. This was a
_very_ good move.

The first waterproof layer went down on top of the polystyrene foam.
As it was polystyrene, not yellow PIR, and was a green roof anyway, I
didn't bother with a moisture barrier beneath. This layer was
geotextile around the edges (didn't bother over the polystyrene foam)
and then a double layer of 1200 gauge polythene DPM. This was then
carefully tucked into a "swimming pool" around the edges and stapled
down to the outside of the upstand. Triangular firrings of polystyrene
were used to smooth out all the internal corners before the liner.

I now tested the liner by placing 2" of rain into it over the next
couple of days. Not ideal, but it's why I'd been working in the dark
to get the liner laid beforehand...

An 18"' strip of geotextile along the lower edge started the formation
of the 4" square shingle drainage gulley, as described in the
livingroofs guide. Their drain is a vertical outlet commercially
moulded into the liner (and outside the building plan, through the
eaves). Mine (as I had no eaves and didn't want an indoor drainpipe)
was PVC drainpipe, cut in through the side of the upstand. I sealed
this to the liner itself with bitumen mastic and hope. With the liner
in place, and the gulley liner held in place with masking tape, I half-
filled the shingle load to hold it in place.

The drainage layer of the main roof (a crucial aspect) was 1"
vermiculite (600 litres). This sits waterlogged beneath the soil
layer, so adds no insulation, but it's lighter than an equivalent
volume of soil and _far_ lighter than an equivalent water retention
layer of soil. This vermiculite was loose laid to about 1" depth (at
this point the rain switched to wind - being lashed with flurries of
damp vermiculite is delightful) and then a layer of geotextile over
that.

Next step was to begin soil loading. This was lifted bucket by bucket
(rope lift is easier than ladder carry, but a gibbet or gin pole would
be even easier) and first dumped around the edges to anchor the liners
down. A shallow sprinkle stopped me walking directly on the
geotextile, especially as I was now back to my digging boots, rather
than roofing slippers. As filling went on, I filled and shaped the
shingle gulley to match.

Total soil load was 3", which was 21 barrows (I was using a small
barrow), maybe 150 buckets. This took three partial days, spread over
months, to complete! The first day shifted the most, enough to
anchor, fill the edges and cover the liner from damage. After that,
and in the depths of winter, I became lazy.

To neaten and weatherproof the outsides, I attached 10" vertical
fascia board of Versapanel - a cement fibre board like concrete MDF.
This is weatherproof when painted. There was also a narrow capping
strip of the same, glued down crudely with mastic.

Planting has been done on the cheap - I have about £20 of assorted
sedum and sempervirens up there, which I hope will spread in time.
There are also a few handfuls of cheap crocus or similar small bulbs.
Then there's a boxful of mixed wild flower seed and also some basic
lawn grass seed. Patches within the roof are full-depth plain sand (no
soil), also some stacked broken bricks, stacked short bamboo tubes and
lumps of branchwood to give a variety of bug habitats.