Water ingress through a lintel

[mmb]

Hello all, new here ... I own a 1850's sandstone rubble Manse and Chapel in Northumberland

Hoping to get an opinion on a problem that occurred yesterday in the storm we had across the UK

Yesterday due to the wind being south easterly we had rain / sleet driving against an elevation with an upstairs sash uPVC window and directly below a GRP covered pitched roof which is part of a conservatory added about 25yrs ago. The join between between the pitch roof and the sandstone has a piece of flashing attached with roofing sealant (to accommodate the uneven sandstone rubble). The long term plan is to replace the conservatory as it's seen better days and correctly flash the connection between the house so it's installed with slits into the stone however in the meantime we have to cope with how it is.

Yesterday we saw significant (2 buckets worth at least) of water which was coming into the house where there is a wood french door is under the pitched roof. At first I thought the sealant on conservatory roof flashing had failed (we have had it redone about 6mths ago), but on inspection it looks okay. What I noticed however is the sealant between the bottom of the sash window and the stone sill has a 5mm gap running most of the way along (which I'll repair today now the rain has stopped)

My question is does it seem plausible that driving rain could go under the uPVC window sill, get driven behind the stone sill down the rubble wall (internally through the sandstone and lime motar) then saturate the stone lintel below (where the french doors are), seep through that stone lintel and then drip down two buckets worth in a day ?

It's worth noting also that the pointing was all redone last summer (it was done the right way with lime mortar after scrapping out the old mortar)

Hopefully my message isn't too incoherent, it's hard to explain in writing

Thanks in advance for any thoughts / PoV

 

[Robola]

Yes, very plausible. There will be voids that allow significant quantities of water to track through the wall. A 5mm gap is large and given the rain yesterday if the wind direction was driving it against that window then you will get ingress.

 

[mmb]

Thanks Robola, that's helpful

 

[fernicarry]

Agree with @Robola I've had fair amounts of water dripping into a downstairs window recess from a poorly sealed sill upstairs. Measured more in pints than buckets though. Even a tiny amount getting through over a long period of time will wreak havoc by saturating joist ends and lintels whilst remaining largely hidden. Something to stay very much on top of.