Leak. ?? from where.

[jo66]

Main roof replaced & joined onto a new extension 3 yrs ago.
Old part of the property has 14 inch thick walls, the new part as per building regs..... the building is now L shaped.

Where the two areas meet we have a problem. Inside the hall at the top of the wall are two damp patches.
The hall side of this 14 inch wall is boarded , the end of this wall is new block & also boarded. ( dob & dab )
The room on other side of the 14 inch hall wall is NOT boarded & shows NO damp at all.
One patch of damp is fairly high up near the ceiling, the other about 18 inches down .... ( & has an area of dob & dab behind it. )

Out side walls are rendered, with a fascia & guttering. The valley has been replaced with an extra wide sheet of lead. Walls painted with Dulux exterior paint.
Guttering is the standard round.

There is no damp in the loft. NO signs of leaks, or water stains anywhere.
There are No pipes in the loft & no water tanks.

The rendering was put on after the fascia & gutters. But we cant see how this could could be the cause...... Checked out it appears OK.

If the rain is ........ heavy / flash storm .. the inside wall is very wet within 4 hours or so.
If the rain is steady drizzle / fine type then it takes a a few hours longer.

Last week during a flash downpour was the first time we have seen the gutter in that corner overflow...... ( Gutters are clear & downpipes )

We need ideas...... can anyone please help us.

 

[RedHerring2]

Where the two areas meet we have a problem. Inside the hall at the top of the wall ...

It seems to me that you need to be more specific about where your leak is. Not in relation to the walls, but in relation to the position of the leak within the joining of the new to the old.

A picture or two speaks a thousand words.

 

[SurreyRoofingEstimator]

Yup, pic would be good but condensation would also be an option

 

[jo66]

Hi,
Thanks............Dont think its condensation.
Had this problem since 2009, theres no mould or black areas.
Just a strong damp smell after it rains,
and for days after till we dry out a bit.

There is a radiator below one area.

As for sending a pic theres nothing to see. Apart from the pencil ring around the damp patch..... 18 inches or so below the coving.

Did a drawing, but so far havent been able to get it onto this e-mail page.

If I said...... the highest damp area inside the hall on the 14 inch thick wall starts about 2 ft inside from where the valley ends at the gutter on the outside.
The round damp patch is on a hall partition block wall.... just after the end of the 14in wall. this partion wall is twix D/R & hall
This round patch is 7 inches wide & 9 inches long.
When the wall is sounded the noise made in that area suggests its over a dob& dab blob.
It was first noticed because of the effect on the paint when the light was on in the hall. After that we checked everywhere with a damp reader.
There is no damp in the D/R at all, on either the 14inch or block wall.
The 14 inch wall is not boarded in the D/R.

After a heavy downpour this evening the fascia box checked .... but found to be bone dry.

Every section of this roof was taken down in January 2009, new felt
new black strips ????? under bottom row of tiles. Some existing tiles used on rear roof .....but not in this area. these all new.
as is gutter & pipes.
Have since had F/glass valley removed & wide lead fitted instead.

All other areas fine..

 

[Nige F]

The valley has been replaced with an extra wide sheet of lead. .

)

.

By a proper leadworker ? This is where I`d look first- the devil is in the detail

 

[jo66]

Thanks............. Yes it was a very well known & well thought of local company that replaced the lead. Including putting a larger saddle on the top.
They even checked where the walls join...........

We have had 4 different firms at this roof.

The last lot again could find no signs of a leak & have suggested coming back during a downpour.

( Thats easier said than done......! )

 

[RedHerring2]

http://www.leadsheet.co.uk/9f-pitched-valley-gutter-lining
Aa Nige said, devil is in the detail.
The above link indicates the detail that needs to go into a valley gutter.
There's three basic 'barriers' to water ingress, mortar, wooden fillet and welt.
Also the membrane should just lap onto the lead.
Any part of that missing could allow water to leak into the roof space.
There are other sites ahowing such detail, just google "valley gutter".
And as Nige said, it's the first place I'd look.

 

[jo66]

Thanks ............. have at last sorted out a few pic's.

The internal wall with Elec box to one side is damp at the coving edge
... this is about 2ft in from the corner where two walls join more or less under the valley.
The other internal is the end of the 14inch adjoining partion block wall.
theres a shaddow down the wall.But you can just about see the pencil mark about 18inches down.
came in after out for 5 hours, heavy rain, place sticks of damp, & damp meter clicking away like mad.

 

[jo66]

Also added several roof pics..... including lead at gutter.

 

[Blagard]

Nigel F is right about the devil in the detail.
RedHerring2 gives a link to a typical lead valley detail.

Your "extra wide" lead give one clue. I think it unlikely that the detail behind the mortar is correct. However on the upper part of the roof, this may not be a serious problem. At the eaves I can see the roofer had some hassle getting the eaves course right, because it kicks up so much. The closeup photo shows the tiles sitting on the lead at the same place. So your lead is almost flat just before discharge in the gutter where the volume of rainwater is the highest! Without welts in the side of the lead at that point (No space for them in your photo), I would think there is a chance some rainwater is running sideways off your lead valley, especially if the lead is not supported properly.

I would be inclined to ensure that a welt is introduced to the sides fo the lead valley, at least to the lower tile course where it flattens out. Given that you have practically no space to do one as the detail, you should at the very minimum fold the side edges of the lead back over.

Unfortunately, your options are very limited by the poor eaves detail.

 

[datarebal]

Well it does not look the usual lash up...
However, based on whats on view at gutter level i'd say the lead is not extrat wide at all. How wide is it? as others have said the detailing under the tiles may not be correct. or very likely there is muck in the wrong places drawing water over the edge of the lead.. very common mistake.

 

[jo66]

Hi,....... thank you.. Your thoughts are most welcome.

But since we have had these flash storms in the last two / three weeks this place is really wet.
On Thursday evening we pushed our son into the loft ...again with the damp meter.
It appears that the wet / damp area now extends along the whole of the 14 inch solid thick wall to the gable end. The gable end is also very damp in parts.
The gable end is a solid 12 inches thick ..
We now are wondering if it could be the roof mortar & or render ???? that is acting as a wick, and because these walls are a mix of stone & brick & rubble we have been lucky not to see any other damp areas.
In our case rain water is soaking down & then along. ?????

PS... the lead on the valley is turned over at the edges to stop water running off it & back inside.............. so we are told.

 

[Nige F]

the lead detail you describe is fine But it seems odd the gable end is wet - I feel that I can`t help much more without actally seeing the house - and I doubt it`s in E. Sussex or Kent . I must admit I wondered a few posts ago if it was not the roof but the render

 

[jo66]

Thanks Nige F,
We have thought about the cause being water getting into the fascia box, because that was insitu before the walls were rendered. so theres an area of old untreated brick behind it. But how would it get wet .
Again the damp meter has been inside that fascia in various places & its bone dry.
We wish you could see the place, but your way down south .......
I could e-mail you with pics if you agree of the gable end before the new roof, and also the post code so you can see on google street maps the new roof ........ but......... its before the wall was strengthened & then rendered, then painted with the Dulux plastic wall paint.
The gable end did look a sorry site..

 

[Nige F]

Thanks for the e-offer, now added you to my "friends" you should find eMail in my profile but it really needs eyeballing in situ . I have a couple more ideas - bearing in mind my experience is not in installing roofs , it`s doing the leadwork and also building maintenance where we found " latent defects" - Anyway , I wondered if the new roof has a breathable membrane , something I am not too fond of , which may be 1 condensating on the loft side runing down. 2 not reaching over into the gutter to discharge any water getting past the tiles . The tiles should not need a membrane but they may not have enough lap to suit the storm conditions - or may have a broken section of interlocking side .

Also the wall construction appears to be , in effect a sponge with a hard layer on the outside , making any ocasional wetting evaporate internally . Maybe the loft space could do with more air movement through it via retro fitted soffit vents . A gale blowing through a loft is not such a bad thing, provided it`s kept away from the living areas by thick insulation ...