water ingress masonry walls 1

[rowingengineer]

I have a conundrum; Three storey unit, concrete floors, with single skin masonry walls (Possibly fully core filled).
Problem is that water is penetrating the inside of the house through the walls (I believe not windows, or penetrations). My theory is that this is occurring through the masonry mortar interface.
Am wondering if anyone knows of a good test system I can implement. At the moment I have a few not so good ideas. ASTM E 514 Test seems to be a little to $$ for me at this stage.
1. Water the wall for a period of hrs/days with a garden hose
2. Tape some plastic to the walls
Second conundrum: There could also be a problem with the painting of these walls, that allows the water to build up behind the paint and slowly leak thought the masonry. One lot of paint 18 years old, second coats, 4 years old. Theory is that the paint 18 years old has started to disintegrate and allow water to trap behind the new paint.
Not so good idea: tape a collecting buck to the wall and pour water against the walls and see how much stays.


An expert is a man who has made all the mistakes which can be made in a very narrow field

 

[hokie66]

Single skin block walls depend solely on the external barrier coat for watertightness. So if the leakage is through the wall rather than the windows, the coating is faulty, whether the old or the new or a combination of the two.

 

[msquared48]

I agree with Hokie here.

And if the house is older than 40 years, I would look to the foundation drain being plugged, raising the water table against the wall. Might have to excavate, repaint, install new perimeter drains, and fill with permeable backfill.

By the way Hokie, I didn't know you were a poet! Did you know it?

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[hokie66]

A poet and don't know it. That is about my extent. Reading the last line, it does have a bit of a creative ring, but I assure you it was unintentional.

RE,
If the original coating was 18 years old, I think that is likely your issue. The acrylic coatings used here in Australia are better (and cost a lot more) than typical house paints in the US, but they need attention about every 8 years, certainly not more than 12, depending on the exposure.

 

[Ron]

RE...hokie is right about the exterior coating being the only waterproofing barrier. Unfortunately, "face-sealed" barrier systems don't work so well on masonry...here's why.

Your old coating probably had quite a few fine cracks in it, particularly at the mortar joints. This allows moisture in and out. The concept of "breathable" coatings doesn't work very well in practicality (in theory they work to some degree; however, a steady state is assumed for pressure and thermal differentials, and that just doesn't occur in walls). So any moisture that gets into the walls must also get out by the same path. Well, for cementitious materials (masonry, mortar, stucco, concrete...), when moisture gets in they expand. As they expand, they close those fine cracks even tighter, thus, the exit path for the moisture is no longer there. After the source of the moisture abates, the cementitious material reaches equilibrium, sheds some of its moisture to the inside (cooler), and shrinks again, re-starting the cycle. If there is a long time between rain events, the moisture will shed to the exterior as well, thus reducing the moisture content of the cementitious material even more. That's good for the inside of the building, but not so good for the coating, as the fine cracks open up again, and sometimes even moreso because as the coating ages, it gets brittle and is more susceptible to cracking.

Along comes a new coating. It covers most of the cracks and entraps any moisture that is in the cementitious material. Further, the new coating will prevent moisture intrusion for a while, but will eventually shrink, harden, and crack particularly at mortar joints. The time for this to occur depends on the quality and thickness of the coating.

Masonry materials are dynamic. They shrink and swell with moisture changes. The mortar moves differently than the masonry because of differences in density, cement content, porosity and materials. That's why you often see pattern cracking along mortar joints. Yes, installation/application has a component in there as well, but even without installation issues, separation often occurs.

So, cutting throught the long-winded drivel, your problem has several facets. The mortar joints, the two coatings, and the inability of the wall to shed the imbided moisture because of the coatings.

Testing will show you this, but as you noted, proper testing is expensive. Rough testing, as you proposed, is fine to show the concept, but I would isolate the area and spray small areas at a time to see the effect. Use a borescope or other means on the inside of the walls to see the intrusion pattern. Infrared thermography can be effective for this as well. Infrared thermography will also tell you which cells are filled with grout.

Good luck.

 

[structuresguy]

question. Would having a water repellant admixture in the block help in the case of painted block? We usually only spec the admixture when the block is to be exposed (ie not painted). But I wonder if it would help keep water from absorbing through the block, under a failing paint system. of course, does the paint adhere properly to block with the water repellant admixture?

 

[Ron]

structuresguy...water repellents in the block mix have limited value. They are generally used for decorative block that won't get painted, as they can cause adhesion problems with latex/acrylic coatings on smooth block.

If they were good at being water repellents, they would cause problems of water-cement interaction within the mix (longer set times, etc.).

Admixtures that are sometimes used as block water repellents in the mix are also used as spray-applied water repellents (Prime-A-Pell 200 for instance). They are much more effective in that mode; however, they only last a couple of years at best.

 

[BAretired]

Add a rain screen, perhaps?

BA

 

[csd72]

What they would do over her is add an internal membrane then add an internal skin of brickwork to hold that in place.

 

[rowingengineer]

Thankyou gentlemen your opinions give me confidence in my thoughts. However I would like to expand on the water resistance of the masonry units. In my opinion the masonry unit relies on a few systems to stop water entering a building. 1. Paint 2. The hollow core

As Ron explained the block soaks up the water, however I thought the hollow core would allow the water to condense on the inside of the block. The water would then travel down the inside of the block on the concrete floor and hopefully outside due to a recess.

The unit I am dealing with has as normal has both fully core filled and unfilled masonry. The un-core filled area’s seem to be water resistant thus far, however the fully core fill shear walls are leaking like sieves. Sorry Ron this is from hammer and sound test not Infrared thermography. So my thoughts are that the water is getting past the paint, and then traveling in via the masonry mortar interface inside.

The reason I want to be able to test it to show concept, because as these things go there has been many investigations before mine, with five different conclusions. 1. The windows are allowing water in, however there are no water marks near the widows. 2. The roof is leaking, which is true the roof is leaking but for the ground floor to get wet from the roof without any other floor getting wet, seems unlikely but I will investigate the roof anyway for leaking and ceiling damage. 3. Penetrations from the air con are allowing water to pass in, but the peno’s and wet spots are different walls. 4. Rising damp. 5. The paint has failed only in the cored filled area.

As you can see I need to gain the confidence of my client as they are starting to doubt any report on the units. So I want to be able to show the paint has failed combined with the water travel path.


An expert is a man who has made all the mistakes which can be made in a very narrow field

 

[Ron]

RE...the filled areas have no means of allowing water to dissipate and changes phases (liquid to vapor). They only allow direct ingress by capillarity, thus condensation and manifestation appear on the inside face of the wall, not the inside face of the core shell.

You're on the right track...keep going. The other conclusions don't "hold water"...sorry, couldn't resist.

 

[hokie66]

Why do you discount rising damp? If the problem is only on the ground floor of a 3 storey building, rising damp would have to be a suspect. For the same reasons as Ron stated, the filled cores are more likely than the unfilled ones to wick moisture from below.

 

[Ron]

hokie66...no need to discount rising damp, but it usually has lower potential for occurrence than wall ingress. Sometimes the crack in the masonry at the floor line is sufficient to form a capillary break.

Rising damp has a different moisture signature than wall ingress. There's usually an indication of moisture at the floor line, (including free water inside or very high baseboard readings), with a rapidly decreasing moisture content above that point. While the same occurs with wall ingress, the moisture gradient is less pronounced.

Unless the groundwater level is at the slab level, or there is very poor drainage at the slab level, I would lean toward wall ingress above rising damp.

 

[rowingengineer]

Rising damp has not been discounted yet, it is unlikely because of the reasons Ron has noted, aka the building is in a sandy loam area, with good drainage. I would also expect problems with floor linings to be more consistent/massive along the wall if rising damp was the issue.

An expert is a man who has made all the mistakes which can be made in a very narrow field

 

[hokie66]

If it were rising damp, there would be a tide line on the inside of the wall.

Without seeing it, it sounds most like a failure of the coating. The original coating was probably degradated to the extent that it should have been removed prior to the latest coating. Single skin block walls have this inherent disadvantage when used for exterior walls. The owners could try again, properly preparing the surface this time, or it may be time to bite the bullet and install a cladding system.