Temporary repair to mortar chimney flashing

[expat paul]

Hi,

I have a leak in my roof around the chimney breast which I assume is a problem with the mortar flashing. I would like to do a quick fix now, as the weather is not good either raining or sub zero, and a full repair in a few months.

I was thinking of a coat of bitumen based paint 'Aquaseal' on the flashing and maybe a coat of waterproofer/sealer on the chimney render, in between the rain and snow showers !!

Anybody know if this will work or has other suggestions.

Thanks

 

[shan Fr]

Hi Paul
The French love there mortar flashings and most flashings are mortar but I have seen one or two that have used Zink.

The tiles or slates will always move and brake or dislodge the flashings, it tends to just break away from the abutment or chimney and leave a gap. This is where the water gets in.
It could a problem with a sink back gutter if you have one if so coat that as well
Both of the tings that you suggest should work for a while.
If there is a gap in-between the mortar and the chimney I would get the mastic gun out first and fill the gap then do as you have suggested.
Before you apply brush the mortar with wire brush it will help it bond better.
But remember its only temporary and you should do the job properly as soon as the weather gets better.
All the best from S W France

 

[expat paul]

Many thanks for the advise, I have one question if I may and excuse my ignorance but what or where is a "sink back gutter"

regards from Chartres

 

[shan Fr]

Paul
let me start again as I had just got up when I replied to your post.

A chimney exiting through a sloping roof will have a back gutter .The back gutter will kick the water from the back (the highest point that the chimney exits the roof) to the sides and down the roof.

In the Uk back gutters are made of lead and so are most flashings on side of chimney..
But it is rare for the French to use Lead ,They use Zinc for back gutters and cement/mortar for flashings.
Now in time Zinc will ware out or split at any of the welded joints and then let water in.
Or where it is fixed into the wall can come away and leak back on its self. Or as I have seen hear in France its not fixed into the wall ,they just put cement / mortar over it and this can crack .
But deepening on the state of the tiles above the back gutter ,it could just be a broken tile/slate . as the water will just run down and under the bottom of the back gutter and the show on the chimney .
But if the water is showing on the sides or front of the of the chimney then its most probably the flashings/mortar on the sides or front.

But it has been known that if the top of the chimney is open to the elements and has no cowl then the water can run down the inside an at some point work its way through the chimney .

So hopefully you can get the idea of it all now that my head is in the right place

If you need any more info just ask , All the best good luck

 

[shan Fr]

 

[expat paul]

Thankyou very much, all is clear now. I will make a quick fix this weekend and then a full repair when we get some sun.