Condensation or Penetrating Damp? Top inner window sill

[Geoffrey919]

Hi Everyone, hope you are all keeping warm and well.

I'm hoping some damp experts out there can help me out with this one.

My living room window has damp on the inner top window sill. My first thought was condensation but its discoloured and feels wet to the touch (which I only spotted from doing back stretches on the floor).

The heating has been on the past few days as its due to it getting colder and hoped it would have dried it up.

I've taken photos to show this issue and have drawn around in red where the issue is, it's along the whole top part of the window sill. I've also take close up shots outside of the main areas where I think water or moisture would have gotten in externally.

I had the windows installed 10 years ago and think the sealant has become loose during that time.

Would you recommend I strip out all the out old sealant or consult a builder for their recommendation?

further note i did scan the attic to make sure there was not a leak through the roof also.

 

[crank39]

If the damp is at the top inside you can disregard everything outside that's lower than the leak apart from your last picture, if this is a bungalow it's worth just lifting up or pushing up the 1st row of roof tiles to see the condition of the roof felt, it could be that it's rotted away upwards and has dropped down behind the fascia so any water running down the felt isn't going into the gutter but is dripping onto the inside of the soffit and possibly running backwards over the top of the window (if the soffit is fitted on top of the window, usually are) and is wetting your reveal, the cause could be anywhere along the roof and water could be running from one end to the other so it would all need checking

 

[Geoffrey919]

Hi @crank39 Thanks for feed back and for pointing this out, its totally something I wouldn't have considered. I'll try to get my hands on a taller ladder that will allow me to have a closer look. I did have peak in the attic yesterday and couldn't see anything out of the blue, granted I didn't get right up the corners of the building internally. Thanks again Crank.

 

[crank39]

Cheers, see water doesn't run uphill so I would check above the window first, it's very common for the old bitumen based roof felt to rot from the bottom as that's where it's lapped into the gutter, all that standing water and the sun eventually takes its toll, lifting the tiles will confirm this, here's some generic google pics to illustrate what might be happening

You can buy these eaves guards from anywhere now and they slip under the rotten felt and lap into the gutter, bread and butter job for a roofer but it's also defo a diy job

 

[Geoffrey919]

@crank39 you are a legend!!

I can't thank you enough, not only do I have a very clear visual cue of what to be looking for, you also pointed me in the direction for a product for the job. You've taken a fair bit of guess work out of the equation for me. I'll secure a ladder first and see how things look from outside.

 

[JohnD]

looks good idea.

it it stiff plastic?

 

[crank39]

Yes rigid plastic, it's specially for the job described, it won't sag between the joists so supports the felt

 

[JohnD]

I used a strip of DPC on my shed, does the job but not so good.

 

[Geoffrey919]

Ah I found the culprit which ended being slightly further up.

Looks like a roofing job and not sure if its something I can do on my own accord. I guess a proper job would be the re-sheet the roof from the top?

On a positive note its good to know something similar to eaves guard was used.

 

[crank39]

A ah you already have them and bird comb's too, no doubt fitted at same time as your soffits and fascias were, it looks like now you will need to have the first 3 rows of tiles removed to replace the first run of felt, no need for the whole roof to be done

 

[Geoffrey919]

haha yeah I had no idea it had birds comb too although I do miss the sound of birds chirping if not the nests. Looks like they did a great job. Think it was pre 2010.

Looks like I will need to strip off the wooden batons to ensure that I can fold new felt under the 2nd run of felt. I'm looking at 135G High Performance Breather Membrane Roll.

 

[crank39]

Yeah use breathable membrane now, it's tough, waterproof and doesn't rot