Damp walls on extension

[DM7]

Hello,

A friend I have previously done lots of work for has asked me to repair a damp issue in his dental surgery. The damp problems mainly occur in the staffroom area located in an extension of the main building.

The extension must have been built around 15+ years ago, and this damp issue has always been present since the time my friend purchased the surgery (like maybe 10 years or so ago). He previously had someone come to repair the damp issue, and that repair guy basically replastered the wall, after installing some metal foil stuff to prevent the damp coming back. It lasted around a year, but the damp came back, and has been getting worse ever since.

I am not a damp expert, and so I thought to ask on this forum to see if there are some experts on this topic who can guide me on how to identify the cause of the damp, and the solution to repair the walls.

NB: I will say in advance, as I know there are some idiots on this forum who think the worse of others, jump to conclusions and just like to chat rubbish and spread hate (as has been the case when I previously posted onto this forum for help) I have told my friend that I am not sure what the cause of his damp issue is, and I have also sought his permission to post images of the damp onto this public forum, to see if other experienced traders are able to guide me on establishing what the cause of his damp issue is. Also, I will add that I have been in the trade for around 9+ years now and am very capable of doing general building work, and once I know what the solution to the problem is I should be able to sort it, otherwise, I will need to pass on this job, as already explained to my friend...


Some images of the building and damp:

This is the extension. All the ground floor internal walls have damp, inc. a small amount in the upstairs toilet room:

The damp on the wall in the image below is the back wall of the extension, where it joins the main building:

The side wall of the extension:

The damp on the wall shown below is on the wall at the end of the extension (that part that has the lean-to roof). The damp starts at the bottom of this wall and goes up higher than 1.5 meters, so I am guessing that means it's not rising damp? (at least on that wall)

(close-up of the same wall that's in the image above)

In the image below I put a green arrow pointing to where there is some damp/mould. I put a green square around the black box. This black box is a water tank that is used for some machinery that needs water to lubricate it. I was wondering if this water tank could be evaporating water and causing the mould/damp where the green arrow is?

The upstairs toilet room (part of the extension) has some minor mould issue that keeps coming back:

The extension is colder than the main building. There is 1 air vent downstairs (next to the black water tank) and there is also an extractor fan in the extensions upstairs toilet room.


Thanks!

 

[securespark]

Is there any heating in the extension?

Leaks from guttering outside, that kind of thing?

 

[Notch7]

A 15 year old extension should not be suffering damp issues.

1) you need to rule out condensation

2) silly Q but is the extension a cavity construction or single skin: the internal window board is very shallow and so the door frame is has no reveal on inside, although big one outside.

3) if there is a cavity, you should probably expose it somewhere - maybe knock off windowboard if there’s damp below the window, have a look see if the cavity is damp

4) if there’s a cavity, you need to make sure it extends below internal floor finish

5) I can’t see how ground level compares to floor level inside - check if DPC is bridged

6) check if external finish bridges DPC - it should stop a DPC with a bell cast trim and brick facework below. Render should not go to ground

7) I doubt there is a cavity tray where the extension abuts the main house, it needs checking

8) is there a vertical DPC where extension abuts house

9) is there a DPM and does it tuck in at DPC course


The above are the basic elements that make up the damp arrangements used to create a complete damp proofing envelope and that’s where you need to start looking as a modern extension should contain all the above

 

[Old Salt]

I am not a builder or a damp expert but I would be wondering what’s going on behind the render especially the corner join where concrete line is and where it joins the external window cill. There looks to be black in the bottom corner. Also what is the soil/ground level in the second picture where the gate can be seen.

 

[foxhole]

If that hopper is blocked then during heavy rain the entire corner of the property will be getting soaked , if the render is damaged then is will soak thru quickly and cannot dry as the render will hold in the moisture .
Need pics of roof level and ground .
If the extension roof to main building was not done correctly then it presents another ingress point.

 

[DM7]

Is there any heating in the extension?

Leaks from guttering outside, that kind of thing?

Yeah, there is a radiator on the ground floor (on the wall that has the worst wall damage), and one in the upstairs toilet room.

I am due to go there next week to fix some other things and plan to check the guttering, thanks.

 

[DM7]

A 15 year old extension should not be suffering damp issues.

1) you need to rule out condensation

2) silly Q but is the extension a cavity construction or single skin: the internal window board is very shallow and so the door frame is has no reveal on inside, although big one outside.

3) if there is a cavity, you should probably expose it somewhere - maybe knock off windowboard if there’s damp below the window, have a look see if the cavity is damp

4) if there’s a cavity, you need to make sure it extends below internal floor finish

5) I can’t see how ground level compares to floor level inside - check if DPC is bridged

6) check if external finish bridges DPC - it should stop a DPC with a bell cast trim and brick facework below. Render should not go to ground

7) I doubt there is a cavity tray where the extension abuts the main house, it needs checking

8) is there a vertical DPC where extension abuts house

9) is there a DPM and does it tuck in at DPC course


The above are the basic elements that make up the damp arrangements used to create a complete damp proofing envelope and that’s where you need to start looking as a modern extension should contain all the above

I spoke with the owner today and he said that the extension has been there since he purchased the surgery 15 years ago. He said its probably 25 years old (guessing).

- What methods are used to rule out condensation?

- When I go there next week I plan to check the things you mentioned about the cavity

- I'm planning to take some more photos to share on this thread, to show the ground-level

Thanks for all the points to check!

 

[DM7]

I am not a builder or a damp expert but I would be wondering what’s going on behind the render especially the corner join where concrete line is and where it joins the external window cill. There looks to be black in the bottom corner. Also what is the soil/ground level in the second picture where the gate can be seen.

If that hopper is blocked then during heavy rain the entire corner of the property will be getting soaked , if the render is damaged then is will soak thru quickly and cannot dry as the render will hold in the moisture .
Need pics of roof level and ground .
If the extension roof to main building was not done correctly then it presents another ingress point.

I've added these things to my list of things to check when I go next week.

Thanks

 

[DM7]

-When I spoke with him today he said the render has been done down to ground level, without a bell cast trim. I can double-check that when I go next week.

 

[Notch7]

- What methods are used to rule out condensation?

Condensation would cause mould on the surface and the window would run with water on cold days

If you knock off a bit of plaster and the damp is in the brick, then that will indicate it’s damp not condensation.

 

[DM7]

I went back and checked some of the things you guys mentioned.

1. I knocked off some plaster on one of the damp internal walls and found the brick also damp:

2. I took some photos showing more of the outside of the building:

The internal wall of this side of the building is where the damp goes up around 2+ meters:

The roofing felt was overhanging, but I could not tell if it would be catching water that could then be getting inside

3. I was thinking the damp could be being casued by the pebble dash breaching the DPM, but then I noticed that on one side of the exstention building it does not have pebble dash, yet that wall is still damp on the inside.

The wall without peble dash:

then on the inside of the wall above it looks like this:

-In the photo above I removed the radiator pipes boxing. I checked for leaks on the pipes but they seemed ok. Yet the wall is very damp, even though the outside of this wall has no pebble dash on it. As mentioned previously, the wall connecting the main building to the extension also has some damp at the bottom of the wall.