How to repair external render?

The exterior render around our hose keeps bubbling and breaking up. We have had it repaired several times but it keeps happening. The chap who has repaired it advised us to use brown vinegar to wash away the powder that comes through the paint (efflorescence?). We had a quote to repair it at $10,000 with no guarantee it would work. We don't believe there is a damp course - is this possible? There is no interior damp. We are on a hill on clay soil. Any permanent repair ideas??

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wooshka

Hi @JulieW , this is an external wall looking at the photo? can you do a bigger photo of the area so we can get an idea of what we are looking at.

Exterior efflorescence isn't that uncommon and can be caused by external influences like sprinklers etc?

MitchellMc

Welcome to the Bunnings Workshop community @JulieW. It's wonderful to have you join us, and many thanks for your question about render.

It's great to see @wooshka is on the case, and as they've mentioned, additional images would be helpful.

In the absence of a damp course layer, water can enter the wall and push the render off through hydrostatic pressure. Is it just the lower portion of the wall that is affected?

Some exploratory work likely needs to be done. You could chip away at the worst area and see what that reveals. If the wall is damp behind the blistering render, that's the cause. You'll then need to investigate further to determine how the water is entering. What's on the other side of this wall? Is the ground level higher than what we see here?

Mitchell

JulieW

https://www.workshop.bunnings.com.au/discussion/comment/19312#Comment_19312

Yes, an exterior wall, also the interior wall in the garage. I'll post some more photo's later. There are no sprinklers that touch any part of the house and we don't have water sitting anywhere on the ground around the house. The render bubbles and cracks off eventually.

JulieW

https://www.workshop.bunnings.com.au/discussion/comment/19316#Comment_19316

Hi. Yes, down the side of the house, the inside floor is higher than the outside as the ground slopes down towards the front of the house, although it happens at the back of the house too where the inside floor is at a normal level. When the render has been removed (about 4 times now!!), there doesn't seem to be any damp and there are no signs of damp inside the house. The chap who has repaired it said it wasn't prepared properly when it was originally done but I'm not sure about that as it is in a line around the lower part of the house, not all over.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/72314#Comment_72314

Could the soil under the house be up against this wall and above the damp course line, @JulieW? That wouldn't explain the rest of the issues on the other house walls, though. It is slightly unusual that the majority of the blistering is lower to the ground. That would typically infer that moisture is rising to that level.

If you are sure there is no moisture in the wall, there must be another reason for the render delamination. If you were to have the lower section re-rendered, I'd certainly recommend considering adding render mesh. It's an expanded mesh that helps hold everything together.

Mitchell

JulieW

https://www.workshop.bunnings.com.au/discussion/comment/99508#Comment_99508

My husband removed all the blocks that butt up against the wall and we put course gravel down before replacing the blocks just in case it was a drainage issue.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/116555#Comment_116555

Were these blocks under the house @JulieW? I was more concerned about the difference in soil level and whether the soil under the house and behind this wall was above the damp course line, typically 150mm from the bottom of the wall.

Mitchell

JulieW

https://www.workshop.bunnings.com.au/discussion/comment/99508#Comment_99508

the side of the house slopes downwards and the render bubbles in a line approx 40-50 cms above the paved area.

JulieW

https://www.workshop.bunnings.com.au/discussion/comment/126348#Comment_126348

We aren't sure that there is a damp course - is it possible that there isn't one? I've tried to get damp proof companies to come out and see what they think, but can't get an answer off anyone. I'm reluctant to pay to have it repaired for the 5th time for it to happen again.

EricL

https://www.workshop.bunnings.com.au/discussion/comment/132877#Comment_132877

Hello @JulieW

I totally agree with my colleague's assessment. Water or moisture is getting trapped behind your wall, notice that the damage only appears in a very specific spot on your wall. Not only does it appear in one spot, but in a straight line and then it flows downwards as this type of damage often tends to do.

I suspect that behind your wall a small amount of water is finding its way toward the unsealed side of the wall. It then enters the cement substrate where it tries to find a way out. Due to the surrounding clay soil in your area, the water instead of being absorbed into the soil is being diverted towards the wall. An unforeseen series of events has led to this particular set of circumstances.

What are the options for repairing the wall? Cutting into your exterior wall is possible but not the best way to repair the wall. Cutting from inside the house is messy and will cost a fair bit. You'll be able to waterproof the inside of the wall, but the source of the water must be tracked and diverted away from your wall. You can also cut out a ventilation window in the wall to allow the water to evaporate. But there is no guarantee that it will be able to get rid of all the water.

One other option is to put a sealer on the bare concrete wall. I recommend using Dunlop Damp Proof Waterproofing, this product will have to be specially ordered at the special orders desk in your local store. It prevents rising dampness, efflorescence, and negative hydrostatic pressure. The best part is that it can be painted over once you have a thick enough coat placed on the surface.

Please keep us updated with your progress, we look forward to seeing your wall sealed and repaired.

If you need further assistance, please let us know.

Eric

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