Retaining wall and salt damp

[firefox]

On the weekend I was inspecting some properties, looking for PPOR and there is one I liked, but I noticed that on some areas of the the retaining wall( made of concrete sleepers) paint is lifted,flaking and some bubbles,(look at the thumbnail) left hand side wall first three top sleepers are affected. I am worried it could be sign of salt damp. Is this gonna be serious problem in the future and how it can be fixed?

Thanks in advance

Rob

 

[Nathan]

drainage issue...

remove, line with plastic, backfill with ag drain leading to a stormwater outlet... then fill with bluemtal/roadbase.

It propbably some home job, with dirt behind it. this will create rot over time, and a termite hazard.

 

[vbplease]

Hey Firefox, I think its a simple case of water repellent not being used before applying the paint. Concrete is a naturally porous material, so it will absorb a little moisture and effect the bond between the concrete and paint causing the flaking and bubbling. It probably only occurred in the top sleepers due to run off from the roof.

Its pretty cosmetic really.. you'd fix it by roughing back the exisitng paint, applying the water proof sealant then repainting.

inadequate drainage is a more serious problem that effects the structural integrity of the wall. i.e. the hydrostatic pressure builds up behind the wall, the wall can't support the extra load, so it moves, cracks, and eventually collapses.

 

[Nathan]

whoops thought wa stimber so the termites wont be a prob, sorry for the missread.

 

[firefox]

If this is the case that's nothing serious. I was worried because behind that concrete retaining wall from the center to the right is another retaining wall running about 1.5-2 m height and is made up from red-gum sleepers, so if the inadequate drainage was the problem here then it would be the big issue in that courtyard and instant attraction for termites. I might take another look on the weekend. I will point it out to the agent and see what he or vendor says....

Thanks again

 

[BoatBoy]

Hey Firefox, I think its a simple case of water repellent not being used before applying the paint. Concrete is a naturally porous material, so it will absorb a little moisture and effect the bond between the concrete and paint causing the flaking and bubbling. It probably only occurred in the top sleepers due to run off from the roof.

Its pretty cosmetic really.. you'd fix it by roughing back the exisitng paint, applying the water proof sealant then repainting.

inadequate drainage is a more serious problem that effects the structural integrity of the wall. i.e. the hydrostatic pressure builds up behind the wall, the wall can't support the extra load, so it moves, cracks, and eventually collapses.

Might need to get rid of the paint totally.

Scuffing and painting sealer on top of existing paint will not stop moisture leaching through concrete and bubbling off existing paint that has sealer on top of the old paint, not underneath.

My thoughts anyway

Dave

 

[craigb]

the salt/lime leaching is from a rising damp from the surface being damp, it happens under the dpc corce on rendered and painted surfaces, according to Master builders this can be treated by mixing bi-carb and water, scrape of the paint and apply the water mix and allow a few days to dry and then re-paint, this neutralises the salt, new bricks do this alot , i have not tried this as yet .

 

[firefox]

Had another look, it appears that paint problem is more widespread. Check the photos.

 

[Zeddy]

A bit late, but I'd like to throw in my 2c.

Since it's a sleeper retaining wall, some people do not design it to resist water pressure, since any water will flow through the spaces between the sleepers anyway. So provided it has been designed to resist lateral soil and surcharge loads, it should not collapse due to the material it is retaining. However it may lead to staining of the sleepers if muddy water seeps through the spaces between the sleepers.

This means that some water will enter the concrete as well. This makes bonding of paint to the sleepers quite problematical, as Boatboy/Dave pointed out.

The salt on the sleepers is another thing entirely. If the salt is coming from groundwater, it is not going to stop crystallising and fretting off any paint and even the surface of the sleepers themselves.

craigb, you do get salt growth on newly laid bricks, but that is another matter entirely. The spec you're speaking of is to remove salts trapped within a brick on creation, not to halt ingress of groundwater.

 

[ethereal]

I wouldn't consider this a problem as it is a retaining wall and not part of the house. It is only a cosmetic issue. I'd plant a hanging vine-typed plant up top to cover it. The timber sleepers can and should be treated as part of ongoing termite prevention by a pest controller - this is not difficult or terribly expensive.

Louise

 

[Zeddy]

I wouldn't consider this a problem as it is a retaining wall and not part of the house. It is only a cosmetic issue. I'd plant a hanging vine-typed plant up top to cover it. The timber sleepers can and should be treated as part of ongoing termite prevention by a pest controller - this is not difficult or terribly expensive.

Louise

From what I understand, the sleepers are made from concrete.