Small patch of damp. How do I get rid of it?

This picture shows some damp that I have in one of my external walls. There is no sign of any leaks or water damage on the outside of the wall.

I have sanded it back but it since comes through.

Any ideas on how I can get rid of it.

Cheers

 

Check out what the cable is doing behind that TV outlet. Water could be coming from and via the cable.

Draw this conclusion due to the damp starting at the level of the outlet.

Could be all sorts of other reason like a damp course etc but you need to start somewhere.

 

No point sanding and painting that till you deal with the problem.
It's an old house, so the damp course has likely failed.
How high off the ground is that floor?
Can you get under the house?
Take some wider photos of that room and outside.

 

Will that solve it?

 

No, of course photos won't solve the problem. But it may help people give suggestions.
Having owned an old house and had (and fixed) that exact problem, it would be useful to know:
1. Is it just that corner that is affected, or more of each wall?
2. Is that an outside corner of the building or is that intersecting wall and interior wall? A exterior photo will show that.
3. If it's an interior wall, is one of the rooms a bathroom?
4. Is the TV aerial coming through the external wall? A photo would show that.
5. How far off the ground is the problem? The higher the better.
6. Is there a garden bed against the wall?
7. Or a path sloping towards it?
8. Is the damp course an old slate one? Often visible.
9. What is the guttering like about that spot? A long shot, but worth checking.
10. Are there vents on that wall? Are they obstructed?
That's a start. Photos will answer most of those questions. Then people can chip in with suggestions based on personal experience.

 

I'd be 99% certain that that is "rising damp" due to the damp course failure (so it is wicking up moisture from the ground). The only way to fix is to restore the damp course. There are chemical methods of drilling and injecting into the lower courses of brickwork to resolve this. Google <damp course failure> to read up on it.

Once the damp course is restored, you'll need to wait a few months for the bricks to dry out before repainting.

 

I agree with @Propertunity . The damp is clustered around a tv point... so it is tempting to blame water ingress from above around the antenna or something on the roof (in which case replacing flashing, or getting some silicone involved is normally all that is required), but if that were the case you'd more than likely be seeing the water damage on the ceiling rather than near floor level.

 

@Mark Reed - two methods to address the issue: Chemical as noted by @Propertunity or replace flashing/dampcourse.

You will need to remove the cement render (up to about 1 m - being the height that the moisture goes up the wall) - the render has the salts from the ground water trapped in it and will continue to leach out if it is not removed.

Take off the skirting & render (as above), either cut in a new damp course to the full depth of the brickwork (about 3 bricks at a time), push in new alcor flashing/damp proof course, push in new mortar into the bricks to full depth and leave 1/2 brick and dampcourse without mortar at each end. Skip 3-4 bricks and repeat. Wait 3-4 days before going back to complete the infill pieces of flashing. Lap infill pieces of flashing over previously installed pieces. (Alternative is to use chemical injection of siloxane by drilling holes every 5" behind the skirting and using pressure or gravity feed), render as before.

Allow the brickwork to dry out before rendering and reinstalling skirtings.

It is unlikely that the type of water ingress has been caused by the aerial cable which runs up the cavity.

Work like this is best left to a licensed bricklayer or other specialist.

 

No sign of Mark, the original poster. He may not come back.
I've dealt with this issue twice without removing render and the fix has worked - 8 years and counting for one of them. If this is a rental property Mark might want a less invasive fix. I wonder if Mark will return?

 

Yes which is precisely what I said if you read my whole post

 

@Depreciator - I've gone down the least invasive method as well on one IP, still waiting for walls to stop leaching salts after 8 months but now limited to minors patches. Admittedly, there's something like close to 100m of wall that I treated with drilling & injection, so there's bound to be some slow release of salts with walls that wet.

I've also carried out the complete replacement which, 15 years later, is still going strong.

 

Sorry for the delay but I have returned. It has been a busy week with the property. I will get some more photos to upload tonight. I think I like the idea to the physical barrier with a flashing over that of the chemical alternative. I am having the skirting removed today so I can see if I have an issue behind. I shall update tomorrow.

 

Here are some photos after I took off the skirting. I took a photo of the external which shows some water egress and mould at the top of the foundation stone. The rest of the perimeter looks pretty good behind the skirting. No signs of rising damp.

I did get a 'so-called' expert in to have a look. He rubbed his chin a lot and told me the bottom two courses of bricks needed to be removed. And then gave me a quote for $15,000. What a cowboy and rip off.

 

What did it include?

I'd be surprised if it's confined to 1m of wall only. The external photo shows the wall is salt affected in the cement render and sandstone footing.

 

The quote was to replace the bottom 2 courses of bricks and make good. Of which only 1 metre of the wall is affected.

 

Gee, he would have had his fingers crossed when he lobbed that quote.
Of course, removing bricks in sections, laying a damp course, and then replacing those bricks is the proper fix. But it's expensive.
This is an IP? I'm thinking you don't want to spend a lot of money?

 

He was from Liverpool UK. Say no more..... I am moving into the property. I don't want to spend money on needless work. When I took the skirting off I expected a lot more water/mould/staining. There was nothing apart from a section.

 

$5k for the contractor who does the job, $10k for the PM

 

If you're going to live there, Mark, at least you're not racing to get it ready for a tenant.
So we know the footing is wet and the damp course has failed and water is heading up.
It's an old wall. They look like sandstock bricks. The last fix I did was on my house. It's 120 years old with sandstock bricks and no cavity.
All I can do is tell you what I have done. I'm not a builder, but it has worked a couple of times. Maybe I got lucky.
First thing I did was work out where the water was coming from and deal with it.
Why is that spot so wet? What's happening under the house? That path went down later than the house. Does it angle into the wall? Are there vents along that wall? Wider photos, as I said earlier, would help.
When I dealt with where the water was coming from, I replaced the clay vents with wire ones to increase airflow - the whole space under the house was a bit clammy. It's an easy job to do that. I was thinking I might need a 12 volt fan, but bigger vents and more natural airflow did the trick.
Then I removed the render below the top level of the skirting. I didn't want to go above the skirting because it was very sandy and I could see the whole wall needing to be rendered and I didn't want to have to do that. I raked out some of the joints and vacuumed up all the dust.
I'll see if I can find something tonight that I want to photograph and show you for the next step.
Scott

 

Okay, here we go with Stage 2 of 'Scott's DIY rising damp fix'.
So you've dealt as best you can with the source of the water and do what you can to facilitate air flow under the house. And you removed the render below the level of the skirting and vacuumed up any loose stuff.
1. Then you need the damp course. I have some lengths of 2mm rigid black plastic in my shed. I have had them for ages. They had been used as a damp proof course in a wall I demolished and I saved them. Over the years, I have used them on the fixes I have done. I just cut them to brick width. Bunnings sell rolls of damp proof course, but I have found the rigid plastic easier to use.
2. Then you buy a short saw. Get the cheapest one you can find - maybe K-Mart. Sit on the floor and use the saw to cut along the horizontal mortar line you have exposed just above the floor. It will be lime mortar and will cut like butter. Cut 500mm or so, vacuum it out. Next, slide the brick width damp course into the cut you have made.
3. Then pack the join between the newly installed damp proof course with non shrink grout.
Then move onto the next section.
Do the same to the outside wall.
The above will take an afternoon and set you back maybe $100 in materials.
4. Then you need to deal with the salts in the render. If that render is like mine, it's going to be sandy and 'drummy' i.e. not all fixed to the brick. I made the mistake of trying to take a patch off a wall like that once and sort of kept going - it was like a picking a scab and it all had to come off.
The walls I have done since have had render and then a skim coat of plaster over the top. It's usually just a few mm. I scrape that off and seal the exposed render - can't remember what I used.
5. Then did a new skim coat of plaster. I just use premixed Gyprock bedding plaster.
6. Then I painted.
7. Use battens behind the skirting to refix it.
It's good to wait as long as possible before plastering and painting.
It really doesn't take long to deal with a metre or so and you save lots of money.
Ideally, you'll need to do the same to the outside skin of bricks.
Scott