Leaking loft conversion

[Notontopoftheworld]

Hi everyone,

I'm looking for advice on roofing problems. I had a loft conversion a year ago. The conversion involved a double gable end structure. The gable ends are timber walls with an expanded steel exterior with pebble dash. The gap in between is filled with insulation. There is a small flat roof on the apex covered with lead.

During construction there was a large amount of rain and many, many leaks. Tarpaulins rather than scaffolded roofs were used. I took this in my stride thinking it would all dry out in the end.

Since then a dehumidifier has been used around four hours a day for a year. But stains have appeared repeatedly after rain at about one foot below the old wall-new wall join, pretty much all around the house. A damp meter indicates a maximum value on the stain areas but nothing on adjacent dry areas. The damp areas do spread more widely after rain.

I can see the join on the exterior walls and it looks fine. The loft interior walls are dry. I wonder if anyone has seen a foot-below-join damp problem before and what it might mean about the state of the roof.

The builders have tried to help but I'd also be interested to hear what sort of surveyor/damp specialist/builder would be appropriate to use to get the the root of the problem.

Thanks for any help

 

[noseall]

I know it is a bit late in the year for condensation issues but the stains could be winter hangover?

How are the walls insulated/ventilated?

 

[Notontopoftheworld]

Yes, I thought of that. Previous leaks have left stains that make things more complicated. But they change and it can't be condensation. The stains are localised and register a strong response on the damp meter. If it were condensation, sourced from inside, then the meter response would be more homogeneous. Also there is a very definite response following heavy rain. So when I say stain, read damp. Unfortunalely, I can't comfort myself with the idea that it is a residual stain from last years leaks anymore.

 

[freddiemercurystwin]

Condensation or leaks the builder needs to sort it out. when you say the builders have tried to help what do you mean exactly. there are specialist roof leak detection specialists but AFAIK they usually deal with flat roofs. Apologies for stating the obvious but finding a leak can be a nightmare tbh, AFAIK the only real way (other than re-flashing or stripping tiles/render etc and re-doing) is with a hose pipe starting at the bottom and working up. Even that will only reveal a general idea of the are of the leak which it sounds like you probably know already. Other than that its plasterboard and insulation out and seeing where its damp and track the damp back to the leak.

 

[Cumbrianroofer30yrsexp]

Get a reputable time served roofer in(not a builder) and im sure your problem will be easily diagnosed.I say roofer and not builder.For roofing work you want a roofer and for building work you want a builder.Many builders "think" they can roof as good as a roofer when in reality most cannot.Ive been roofing 30 years and im still learning.Example.I couple of years ago i went on a job,chimney damp/breast,they guy had flashing done,render,new pots and top,he then had it re-built yet it was still damp which is when i was called in.I broke through the chimney breast in the loft space,the flu liner was 6-8 ft short of the chimney top,i had the flu liner extended,no more damp.What im trying to say each to his own.Call a reputable roofer.PS,Expecting to be ripped into by builders slash roofers

 

[noseall]

I personally agree with you Cumbria lad, to a degree.

I build extensions from start to finish including building the roof and covering it in. I am up close and personal with ALL the processes involved with building the whole roof and not just the tiling.

Roofing, in particular lead flashings, soakers, saddles, aprons, back gutters etc, is all about understanding what the water will be doing as it flows down the roof and how that water will behave once it reaches a certain junction or abutment. Even, for instance, knowing that snow will behave rather differently to flowing water.

I am of the belief that going slightly overboard is better than just giving it enough. I have seen contract roofers doing daft things also, in the sense that they are on a tight price so little time will be spared for intricate time consuming details.

I recently saw a window fitters house (front roof canopy) with 6" gauge on plain concrete tiles. He couldn't see what was wrong with it until i laid some tiles out dry and showed him!

That said, out of a hundred builders and a hundred roofers, it would be foolish to assume the builders would win out in the reliability stakes where roofing is concerned.

 

[Notontopoftheworld]

Thanks for the replies so far.

When I say the builders have helped. I mean mastic along the old wall-new wall join and some repointing of a chimney (which we have been asked to pay for).

There was a big hole in the roof felt in one corner. I noticed this during roof construction (it looked like someone had put a foot through it). This caused a lot of leaks during construction. But the leak is pretty widespread so that could not be the whole story.

They did have problems with their roofer who was unreliable and so they finished the tiling themselves once the lead work had been completed.

 

[Cumbrianroofer30yrsexp]

I know exactly what you mean about sub contract roofers on tight scheduals.Whole tiled roofs with very few nailed,ridges not bedded properly etc etc.Me personally i bother with very little new build/contract work as the margins are too tight,I dont even bother to price them these days.SNOW-I once fitted a velux,a couple of weeks later it snowed,the velux leaked,nothing much but a leak all the same.Anyway everything was in order and its never leaked in since,this was(1992 ish).

 

[justlead1]

Hi Is the wall in question cavity or solid? has a drip been formed at the base line of pebble dash? My thoughts are that the rain water hitting the new pebble dash (water proofer in mortar) running down the face and saturating that below.