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I have a roof that has a chimney on the side centre of the house. This means there is a trough behind the against the hip of the roof and around the two sides following the slope of the roof. The tiles are Marley concrete.

The trough has been filled with cement and has lead underneath. The ends of the roofing tiles are imbedded in the render.

There is some damp present in the ceiling below inside the house.

Am I right in thinking that water may get behind the edges of a tile and may therefore be best left 'open and unimbedded' so as to allow the odd drip from the channels on the inside underneath? Will the cement trough not hold water?
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griffithsrj,
The trough should really be a lead gulley with upstands on both sides with the tiles overhanging the upstand and bedded on mortar.
Removing the mortar will probably make thing worse because driven rain will then be able to get under the tiles.
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Thanks for taking the time to reply.
What I meant was they the tiles in render. I could understand them being seated on render but surely some water would come down inside the edges of the tile and have nowhere else to go?
/
chimney \ / tiles
\-----/
render covering ends

griffithsrj,
I don't really understand your reply.
If you are saying the tiles directly abut the chimney and are buried in the render then there should be pieces of bent metal under each tile called soakers.
If you can clarify I'll try to help further.
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Sorry. I will try! The chimney and roof hip form a V at the middle side of the house. The chimney is set 2 feet into the roof and then sticks out some, so looking down appears ------
------| o o |----------
------- tiles
So it has a back gulley and two angled sides running down to the external gutter. There is lead under the tiles and cut into the chimney. The back gutter is filled with cement and the ends of roof tiles end inside the render. Water runs down the hip and into the back gutter.
So I wonder if any water should get behind the tiles then it has nowhere to go. I am thinking of chipping the render out and exposing the tile ends to allow for any drips. Hope I make sense now. Thanks again for your interest.

griffithsrj,
At the back of the chimney there should be a lead apron which is dressed into the chimney, the lead should then drop down the chimney and form a flat this should then rise again with the roof slope ending up well under the first row of tiles.
I would suspect that there has been problems in the past and someone has tried to stop the water ingress by filling the gulley with mortar.
If you chip out the render you are likely to pierce or shear the lead apron.
If you don't fancy replacing the lead use silicone sealant on any splits.
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