Identifying marley tile and roof pitch issue

[doormouse1]

Hi guys,

I've removed the ceiling on a single storey extension and found the plasterboard damp, crumbly and covered with mould on the top (roof void) surface. Now that the roofs exposed, I can see the felt has a number of holes and when there is strong wind and sustained rain, water drips from these.
I've measured the pitch at 15°, so after reading other posts on this wonderful site, it seems to me the tiles shouldn't be at such a shallow pitch and that's why the wind can blow the rain in.

Question 1 - Can anyone name the tile?

They have Marley written in the back and are grey flat concrete tiles with a granular surface.
410mm long and 330mm wide (287 wide excluding the interlock).
Extension roof was most likely added in the late 70s.
The most similar tile on the marley website is the "Modern" but they state this is 420mm long.

Question 2 - What's the best fix?
Don't really want to change the tiles as they match the main roof.
Raising the pitch will be a real pain (but is possible if no other solution).
If I strip the roof, should a double layer of felt (if that's the right word) carefully installed with no holes, cope with a bit of water the three/four time a year it'll blow through the tiles?

Question 3 - If you think this is a viable solution, what type/brand of felt would you recommend? If relevant, roof is 6m wide by 2.9m deep.

Thanks

 

[redtonybbb]

Tb-I think you will find you have marley modern tiles,and if the roof is such a low pitch you can both increase the lap on the tiles ie instead of allowing 75mm allow 100mm as a min.You can further increase the lap on the undersarking ie. from 150mm to 300mm,and fix the lap down on every rafter with clout nails.A good undersarking is protect A1 ask the roofing merchant,as felt on roofs is being replaced by more modern undersarking which does not rot as felt and is more insulating.(Good Luck).

 

[doormouse1]

Thanks for the quick and detailed reply.

 

[noseall]

marleys range of low pitch tiles are only sold in smooth format, certainly not granular.

are you sure they are granular finish?

a photo maybe?

the only marley tile specified for a pitch as low as 15 degrees is a "wessex".

 

[redtonybbb]

Tb-I remember using these granular types a long time ago.(1975-1990)Roofing tile manufacturer normally guarantees for 25yrs.I cannot think of a flat tile which was granulated which was anything other than a modern,I know there are a few additions in more recent years.There was a slight difference in manufacture when imperial was changed to metric.If these are so old they will be like biscuits and easily broken.Granular tiles loose colour and fill your gutters with granular surface over a period of time.

 

[doormouse1]

Mis-communication.
I'm sure the current tiles are not low pitch ones - I think that's why the waters getting in - trying to name the tiles so I can confirm what pitch they are suitable for.
Tried taking picture earlier but the combination of a cloudy wet day and old dirty grey tiles doesn't produce a usable image. may try tomorrow if it's sunnier.

 

[The Roofer]

Tb-I remember using these granular types a long time ago.(1975-1990)Roofing tile manufacturer normally guarantees for 25yrs.I cannot think of a flat tile which was granulated which was anything other than a modern,I know there are a few additions in more recent years.There was a slight difference in manufacture when imperial was changed to metric.If these are so old they will be like biscuits and easily broken.Granular tiles loose colour and fill your gutters with granular surface over a period of time.

Although a marley modern smooth tile might have been laid over 30 years ago. And were smooth when first laid. But now can look granular due to them being worn from weathering over the years. This can confuse people at a glance if they are not in the trade.

A worn tile might have a rough texture. But that does not mean its a granular tile. And this is where some people get confused.

A picture is probable the only way to really tell.