Rainwater/wall cracking/plaster flaking

[CG1234]

Hi all, we have sash window, with a radiator below it. It has been cracking and paintwork chipping a bit over the last few years, but recently it has got worse, and today, rainwater appeared (it was a violent storm tbf). I suspect the main cause is the heat of the radiator/cold from outside. But presumably there is more to this?

 

Can anyone help me by guiding me through what is probably happening? And any advice re fixing the gap which the rain got through, and making presentable again? We are pretty strapped for cash at the minute, so any DIY, low cost advice very gratefully received. I have zero building experience so i may have not used the right terms to describe! Thank you! 

[ProDave]

The defect is probably on the outside relating to the window sill.  Picture of that?

[Russell griffiths]

Outside window cill letting in water, bricks saturated, water getting pulled inwards with the heat from the radiator. 

[CG1234]

Thanks for your replies. Attached are photos of the outside. Assume its a case of sealing around the side/underside of the sill externally, and then patching up inside? The wall is a little damp inside, post rain...would you wait for it to dry before sealing externally? 

 

Thanks again for your help! Really appreciate your knowledge!

[ProDave]

The issue to me appears to be a stone / concrete sill with no drip bead.

 

Normally the underside of such a sill has a groove that encourages water flowing over the edge and underneath to drip off.  Without the drip bead as yours appears to be water is likely to flow to the wall underneath the sill.

 

Can you take a picture looking up from below to the underside of that sill?

[CG1234]

Thanks Dave - photos below! 

[ProDave]

Are they all like that or just this one not having a drip bead?

 

As well as re sealing all the joints, I would scrape off the paint underneath and then run a bead of outdoor sealant along the bottom say about 10 to 20mm in from the outer edge.

[CG1234]

I have just checked and the others have like an indent running along them, a 10mm or so from the edge - I assume that is what this main one should have too?

I assume what you are suggesting is too essentially create our own but with sealant, and convex not concave?

 

Also how would you go about patching up the interior? Will it need a patch of replastering?

[ProDave]

Scrape the paint off and make sure this one does not already have the groove that some decorator has filled in to make it look nicer?  Otherwise a convex bead of sealant will do much the same job.

 

Let inside thoroughly dry out before patching up and re painting so that probably won't be until the summer.

[CG1234]

Dave, thank you so much! Really, really appreciate your insight. Will do the above.