Damp patches in bottom corner of windows. Problem found. Repair advice

[matm]

Hello!
We have been renovating our house over the two years since we have had it and only after decorating have we noticed damp patches in the bottom corners of the windows. Paint starts to bubble with salt deposits coming through (efflorescence?).

Thinking it was bad pebble dashing repairs from the window installers (from previous owners) we had the outside edges re-rendered. On the inside I scraped the salt off and scraped back the paint to pair plaster and re-skimmed the areas in preparation for painting.

I left it for a few days to wait until it rained. It rained and the damp reappeared. After searching the internet again I came across here and several other posts of people reporting the same issue.

Most of the posts I saw said the problem sounds like the window and sill have not been sealed correctly. This inspired me to dig out the corners of the windows from the inside and have another look.

After digging out the plaster to expose the window sill edge I went outside and threw a cup of water at the window and had my partner watch for any leaks...

We didn't expect to see a whole stream of water pouring into the wall!! It seems to be making its way in from nearer the front of the sill.

I'm confidant now that this is the issue for all the windows that are showing this issue.

So my question now is the best way to repair?

My thoughts are...
1. Run a bean of silicone along the window and sill + some extra for good measure.
2. Then fill the rest of the hole with expanding foam filler to help plug up any other gaps.
3. Then skim over the foam and paint.

I've attached some photos of of this journey.

Thanks to gazman16 on here as he suggested many times that it looks like the sill has not been sealed up.

Paint starting bubble due to salts coming through...



Repairing outside..


Damp re-appearing (more salt also started to appear. not in these photos)


Hole made today..

 

[God]

2 things i would look at. Maybe the bay roof assuming that is a roof on top of the bay and also the rain running between the cill and bottom of the window and running back

 

[bobasd]

your water test could have revealed - the issue?
or perhaps there are other moisture issues as well?

the frame looks to have been badly installed.
let me list a few faults:

1. the sill appears flat - not sloped out.
2. the vertical sealing strips on the exterior reveals might need to come off for inspection behind them - and silicone sealing of frame to wall before replacement.
3. the render patch shows no dash.
4. the cavity has not been cav closure sealed.
5. others more qualified than me might comment on the lack of a sealed off stop end to the sill.
6. some sills benefit from a strip of DPC below them.
7. all interior water damaged plaster must be removed.
8. use plugs of sand and cement.
9. what material is the window board?
10. does it have a metal angle bead?


i notice in your post history (ref. jenny) that you appear to have some kind of window "surveyor/installer" claims?
its probable that i dont understand but can you help explain?

 

[matm]

Thanks for the replies.

I forgot to mention that the house is single skin. No cavity walls.

2. the vertical sealing strips on the exterior reveals might need to come off for inspection behind them - and silicone sealing of frame to wall before replacement.

Good idea. Will do that.

3. the render patch shows no dash.

The photo was during the outdoor repair we had done. The dash is back on now with the final render. The photo is to show where we had the repair made....which proved not to be the issue, since it's still getting in.

8. use plugs of sand and cement.

Are you suggesting sand and cement to fill the hole, after silconing, instead using expanding foam?

9. what material is the window board?

We have no window boards. It's just plastered up to windows.

Thanks for all your help!

 

[bobasd]

a blob of S&C to bulk up the hole(s) and when its set you can Easifill for a fine sanded surface.
i dont like or trust foam - altho i occasionally use it!
apply the Easifill in thin layers allowing to dry between each layer.

i know you dont have conventional wood window boards but the (i assume) plaster board and skim on the ledge and stud wall apron
& the the angle bead
and water damage to the inside reveals
typically, all damage has to come off and be replaced with fresh stuff.

remove all but dont be piecemeal filling and replacing anything until you've found & rectified the cause(s).

aamoi: i could remove your frame in about 30 to 40 mins - lots of guys can.
putting it back would take 30 mins
making good who knows without being on site - installing a wood window board is deff the best way to go.

 

[matm]

remove all but dont be piecemeal filling and replacing anything until you've found & rectified the cause(s).

A few weeks ago I siliconed the edges of the frames that are exposed in the holes I made. I since sprayed the windows using the hose and no more water is coming in!!! Before the silcone the water just poured in when I tested with the hose. It has also rained since and its stayed bone dry in the holes. Im confident the issue is fixed for these windows now and ready to be filled in. Just deciding between S&C vs Expanding Foam before using Easi Fill and painting.



Now that we are stuck inside I decided to check our other windows. They all have have lose pebble dash render in the corners.

For some reason I decided to knock off the lose render.....

One window has got very soft sand (could scrape it out with my finger! Guessing its S&C that's a bad mix thats never dried + the rain and wet getting in!?) and one window has a small bit of foam with large gaps. Neither windows have ANY silicone.
The kitchen window wall has actually been plaster boarded and has been showing signs of damp. Also the bathroom has lose and cracking tiles in the corner of the window.




I feel like I should do this for all the windows on the house. Dig out the old render, add foam to all the gaps, add silicone to the windows + sills, and re-render......

What would be the correct way to fix this?

After I foam up the gaps and silicone the frame im not sure how to redo the pebble dash render.

 

[matm]

a blob of S&C to bulk up the hole(s) and when its set you can Easifill for a fine sanded surface.

Is concrete ok or mortar? I going to get a ready mix as I only need a small amount. I see lots of people saying to use mortar to fill holes. is there a difference between concrete and mortar for something like this?

 

[bobasd]

You can buy bags of repair mortar from Plumbing or Building Suppliers - small bags just enough for patching up work.
All you have to do is add water to the mix.

fwiw: concrete is, roughly speaking, mortar with stones added - but you dont need any concrete for the above work.
Mortar is, typically, 3 or 4 parts sand to one part cement.

 

[Johnny Allround]

Hi Matm, did I see in one of your threads that you were contemplating siliconing between the window and the cill on the outside?

 

[matm]

Hi Johnny,

Yes silconing but not along the cill on the front if that's what your asking about. I understand that needs to be open for drainage?
I'm doing it along the cill and frame on the side.



This is what I've done already. There was nothing there previously. It seems like no window has been siliconed like this which is why all my windows are showing circular damp patches in each bottom corner.

The other siliconing I'm planning on doing is vertically up the sides of the frames between the expanding foam and frame before rendering over. The windows all seem to have been put in with no foam as well so will be adding that.

 

[Johnny Allround]

Thank goodness for that you look like your on the right track then.

 

[matm]

.but you dont need any concrete for the above work.

I'll be using mortar then.

But for my own understanding is there a reason not to use concrete?
I have seen tubs of ready to mix mortar and concrete for the same price.
For example
https://www.screwfix.com/p/cementone-general-purpose-mortar-grey-5kg/36857
And
https://www.screwfix.com/p/cementone-waterproof-cement-grey-10kg/58196

 

[matm]

Well...this has been a fun adventure....

After making the holes and testing with a hose by spraying the water at the windows I saw water running into the holes...

I sealed along the sides of the frame and cill with silicone. Left it for a while, it rained no issues, I used the hose....no more water.


You can see the big blobs of silicone....

I then filled up the holes with sand and cement, left it for a few days (forgot the photos of the cemented holes)...

Then a layer of filler, left it for a day to dry out before sanding and painting..which brings us to today.

Today its raining....and its all exactly the same! Its getting wet in the same place in the same way!



I think I give up. I have no idea what to do now. I really thought I had found the problem after making the holes and finding no silicone!

 

[Johnny Allround]

It’s getting in somewhere and running down the frame line. Have you checked around the top of the window?

 

[foxhole]

You are just investigating point of damp not how its entering , probably find the same sloppy fixing down the sides and across the top , need refitting to have any chance of success,[ new render all round]