Slate roof abutment question

I'm re-roofing my lean-to workshop at the moment, and it abuts the side wall of my house. It was previously done using profiled double-roman clay tiles and they used a cover flashing for this. When I started the project I had planned on re-using the tiles and I bought a GRP abutment soaker (secret gutter). I have since changed my mind to slate as this is the same as the main roof of the house.

So after researching I've found out that I'm supposed to use individual lead soakers for the abutment if I'm using slate. My question is, can I use the GRP soaker instead of individual lead soakers or is this only appropriate for tiled/profiled roofs? Also, I've read a cover flashing is not appropriate for non-profiled roofs such as slate and I just want a step flashing that only covers the soakers. Is this right?

Many thanks. Ian

If the GRP secret gutter detail drawing was posted it would help but there is nothing to stop you using one. You would still need to use soakers dressed into the gutter, I don't know how that gutter is sealed to the wall but that detail should be the standard. Personally I do not like secret gutters with lead and slates as if blocked, they can overflow.

The way water runs down a slate roof is rather different to the "channels" profiled roofs have. Additionally because of this your slates have a double overlap instead of single the profiled roofs have. The individual lead soakers of a slated roof are necessary to stop water running around the edge and under the slate, by the time it nearly does that it will be back on top of either another slate or soaker. Pitch is very important because profiled roofs can go down to a much lower pitch so check you have enough before you consider it. The "cover flashing" with slate is just to the wall itself and not dressed over the slate, it goes just over the upstands of the soakers. It can be either a stepped flashing or the apron style set into groove following the line of the roof. Stepped is best for exposed brick walls as you use the bricks bed joints.

Soakers and associated flashings are unlikely to block in the future. Soakers do not have to be in lead. aluminium
is common these days and are inexpensive. They are thinner and less likely to cause your half slates to cock.
They are available from most roofing merchants in various sizes to suit slate or tile size and type.

I would gumtree the grp.

Many thanks for your replies. OK so I'm thinking the consensus is to forget the secret gutter and just use soakers. I wasn't entirely sure how/if the soakers were supposed to be attached to the wall or if they just remain free, as in only attached to the roof, and tuck under the cover flashing?

I was planning on an straight apron flashing for the cover as the wall is pebbledashed stone (it's an 18th century cottage) with a deep 35mm chase. I've heard the chase should be angled upwards into the wall rather than perpendicular to it, is that right?

The top edge of the soaker is bent over to hook over the slate and batten. With the side bent up around the edge of the slate above it and being against the wall the soaker is effectively trapped into position. The cover flasing on the wall finishes off by stopping any water running down the back of the upturned side of the soaker.

I have never done a chase 35mm deep (I usually go 25mm) or bothered to angle it. Providing the lead is properly dressed, fixed and pointed you should not have any problems.

Being some-what ancient I still use lead soakers but as posted above I see no reason why other suitable material cannot be used. If lead, use Code 3 for the soaker and code 4 for the flashing.