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Topic # 161817 20-Jan-2015 20:59
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Hi Guys, got a bit of a question about a leaky garage. Basically it’s concrete block (cinder block? – they appear to be hollow) built 1977, and when it rains water is seeping in through the base of the east elevation where the concrete block meets the foundation. The water is coming through in patches right along the elevation. The water isn’t flowing, just a damp patch that slowly makes its way about 5cm out from the wall.

The garage sits on a concrete slab, and the base of the blockwork is elevated about 6 - 7cm from ground level. There is a strip of concrete that runs along the outside edge of the wall (about 200mm wide). This strip sits about 2 – 3cm below the base of the blockwork (i.e. there is about 2 - 3cm of foundation exposed between the base of the blockwork and the concrete strip). On the outside of the concrete strip is a drain that runs the length of the elevation.

The concrete strip that runs along the elevation doesn’t appear to have puddles, but I can only assume that the water that is seeping through the wall is collecting on this concrete. I had thought that the water could be leaking from the roof and making its way through the blockwork. But the top of the wall is bone dry, and there are no apparent leaks. The foundation doesn’t appear to have used a plastic membrane.

I’m a complete novice. Is this the sort of thing that a sealant could fix? What product would I use, and how is it applied? Is there any risk to the structure of the wall is water continues to make its way through?

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  Reply # 1218606 20-Jan-2015 21:11
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I had this and I tried a bunch of different things to fix it. Not sure if it came in through the painted bricks, through the concrete base, or through a gap.

The soil was above the level of the floor in places for me. Here's what I did:
1. Dug out along length of the shed, cleaned it with the hose, and used mole seal (tar paint) to seal the concrete up to the paint line where the blocks took over from the concrete (it's pretty cheap - use a new/cheap brush as it ruins brushes).
2. Once dry I filled the ditch with drainage rock and drainage coil so water drained away better, then filled it back in.
3. I rolled over the entire wall, down to and over the mole seal, using Sto Protect. Two layers. It cost me $300 + GST and I only used a fraction of the 15L - happy to sell some/all of it on (I'm in Wellington).

This reduced water ingres by at least 90%, almost eliminated it. I did it myself, wasn't too difficult, a professional was going to charge me near $800 from memory.




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  Reply # 1218614 20-Jan-2015 21:17
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take a picture it speaks a thousand words as you terminology might not be correct so it could confuse those in the know :)

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  Reply # 1218616 20-Jan-2015 21:21
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There is also a product that will seal the concrete blocks, preventing water ingress, although not sure of the name. They use it on block retaining walls where you can't get in behind the wall. The solution penetrates it, blocking of it's porosity,  and it is apparently very good, but expensive. 

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  Reply # 1218617 20-Jan-2015 21:29
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mattwnz: There is also a product that will seal the concrete blocks, preventing water ingress, although not sure of the name. They use it on block retaining walls where you can't get in behind the wall. The solution penetrates it, blocking of it's porosity,  and it is apparently very good, but expensive. 


this sort of stuff?
http://www.cemix.co.nz/waterproofing/

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  Reply # 1218631 20-Jan-2015 21:50
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timmmay: I had this and I tried a bunch of different things to fix it. Not sure if it came in through the painted bricks, through the concrete base, or through a gap.

The soil was above the level of the floor in places for me. Here's what I did:
1. Dug out along length of the shed, cleaned it with the hose, and used mole seal (tar paint) to seal the concrete up to the paint line where the blocks took over from the concrete (it's pretty cheap - use a new/cheap brush as it ruins brushes).
2. Once dry I filled the ditch with drainage rock and drainage coil so water drained away better, then filled it back in.
3. I rolled over the entire wall, down to and over the mole seal, using Sto Protect. Two layers. It cost me $300 + GST and I only used a fraction of the 15L - happy to sell some/all of it on (I'm in Wellington).

This reduced water ingres by at least 90%, almost eliminated it. I did it myself, wasn't too difficult, a professional was going to charge me near $800 from memory.


This is on the money.  You need to clear away the earth, seal the blocks from the outside, and drain away the water.  Not to technical, but may be a weekend or two worth of work.  




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  Reply # 1218752 21-Jan-2015 05:40
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Timmay is pretty much on the money.

Where the wall or foundations are covered with soil (or may be covered in soil as ground levels tend to rise over time) then you need a waterproof membrane such as 3 coats of flintcote or similar. The remainder of the block wall should have 1 primer coat specific to concrete/masonry and then 2 top coats of a semi gloss acrylic. Paint all the way down and over the top of your waterproof membrane.

Strictly speaking you should have a chased flashing in the blockwork that protects the top edge of the membrane from water running down the wall from above and in behind the membrane. Considering it is the garage it is probably overkill but if it is a living space or could be in the future then consider installing one rather than relying on the paint adhering to the membrane forever. Lastly don't forget to include this wall when you repaint every 7-10 years.  

Follow Timmays process re drain coils etc.

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  Reply # 1218753 21-Jan-2015 06:10
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Coatings that are applied internally to block the pores in the concrete do not always work and are a second to last resort for stopping water draining through. I find they work about half the time which is less than ideal.

Normally you can't paint the exterior easily when it is a retaining wall as this requires all the soil to be dug up again - not always easy and definitely not cheap.

If you can coat the exterior of the wall - do so. Even though water may be stopped at the internal surface by aquapoxy or hydropoxy type coatings water is still sitting in your blockwork and will accelerate rust of reinforcing bars. It takes decades for spallation (where iron oxidises and cracks the surrounding masonry due to increasing volume) to occur however but it is worth keeping in mind.

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  Reply # 1218776 21-Jan-2015 07:40
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Masarius: There is a strip of concrete that runs along the outside edge of the wall (about 200mm wide). This strip sits about 2 – 3cm below the base of the blockwork (i.e. there is about 2 - 3cm of foundation exposed between the base of the blockwork and the concrete strip). On the outside of the concrete strip is a drain that runs the length of the elevation.

The concrete strip that runs along the elevation doesn’t appear to have puddles, but I can only assume that the water that is seeping through the wall is collecting on this concrete.


The OP hasn't mentioned any soil but unsealed blocks or mortar can absorb water. All advice about sealing would still apply.

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  Reply # 1218782 21-Jan-2015 07:47
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If you put a waterproof coating on the inside of a wall the wall will just fill up with water, and water will eventually get out - though it might get out the exterior not the interior. I wouldn't do it unless there was no other option.




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  Reply # 1218799 21-Jan-2015 08:39
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Ive got similar issue in heavy downpours, managed to solve most of it by getting the council to increase the size of one of the roadside drains/pits so the water didnt overflow into our property so much - still get a bit of seepage but will dig up and lay some drainage etc and hopefully that'll stop it.





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