Wet patches showing in ceiling of newly constructed extension ceiling

[Mdparkin88]

Hi,

I have currently had a single storey extension construction on the back of my property housing a new kitchen.

Since I have had the ceiling plastered a small wet patch was keep appearing and then going some times without any rain. This never occurred when the ceiling was boarded its only ever since the plaster was applied.

After heavy rainfall last night I came across this morning more than one wet patch showing, was just wondering before getting in touch with someone if anyone has ever had a problem like this?

Thanks

Michael

 

[bobasd]

pphotos of the outside of the roof,show detailan the whole roof please.

ask the mods to transfer this to roofing

 

[freddiemercurystwin]

Could possibly be the dreaded incorrect choice of tiles, what's the pitch and what are the tiles and what is the lap? And as mentioned photos and move to roofing.

 

[Doggit]

Who did the roof; yourself.

 

[Mdparkin88]

The roofing works were carried out by a company not myself, the pitch of the roof is 15' with a Marley Mendip tile this was the highest pitch we could get on the roof due to existing window, 100mm headlap on the tiles.

I was given some information from a friend who said because of the low pitch of the roof and with the wind this could be blowing is back up when raining.

Attached images

 

[Doggit]

The headlap under the tiles should be 100mm on 15 degrees, but it doesn't look that much. You've got a membrane under the tiles, and the waters obviously getting under the tiles, and then coming through the batten nails. Have a look at this, and see if the procedures were followed.

 

[datarebal]

Agree headlap is less than it should be.
Are all flashings now on place ?

 

[Mdparkin88]

Yes all flashings are in place everything has been completed, just awaiting decoration internally, will get up tonight and check the headlap is correct

 

[^woody^]

Regardless of headlap, the membrane should deal with any rain that gets under the tiles.

Kick some tiles up directly above those damp marks.

 

[^woody^]

"After heavy rain" almost always means water penetration. But another possibility is the cooling effect which can create a cold surface internally for condensation

If there is an air gap between the insulation and membrane then condensation could form there. Is there eaves and ridge/abutment ventilation?

But if this was right after the heavy rain we had, and especially if the wind was blowing up or to the side of the roof, then driven rain is the most likely.

 

[catlad]

As said headlap looks short but it could be condensation
was a vapour barrier used? is the radiator on that wall?

 

[pilsbury]

Looks like the wet patches are on the plaster board joints. Water might be getting in anywhere above the wet patches and flowing over the top side of the boards till it finds those joints. I’d be investigating high up on the roof first.

 

[Mw Roofline]

Might be worth a few pics of the flashings at the top.

 

[Mdparkin88]

Thanks for all the comments and advice I will get some pictures in the light tomorrow of the flashings at the top, there is no radiator on any walls yet

 

[John D v2.0]

Was the membrane draped between the rafters to provide a channel for water to run away from the nail holes or did it get pulled tight?
Edit no idea what a mail home is, thanks @Ian H