OMG FILE: “Mites go up and tites come down”

Nope! This is not an icicle. It’s too warm outside, the grass is growing.

Stalactite

This is overhead at the top floor rear balcony of a 4 floor condo building that is less than 10 years old. The edge we are seeing is the concrete roof slab which extends out to cover the building-wide balcony areas.

So it’s not an icicle. So what is it?  Well even though this is not the roof of a limestone cave, it is in fact a stalactite.

Yes a mineral deposit from chemicals leached out of the concrete roof deck. The chemistry here is closely related to that of the limestone caves although slightly different.

That variation is not so important as what it tells us about the building, it’s roof slab and the roofing membrane. This one is large for a concrete stalactite and indicates a rapid build up which means a concentration of water seepage flow here or a lot of that water flow.

Look at the pale whitish area leading to that ‘icicle’. It has a little ridge of the same deposits along its length and darker ‘wet’ staining on a wide surface on either side. This is sign of a linear crack in the concrete through which this water is seeping.

Without having seen the roof membrane materials we already know that water proofing membrane has been compromised. I didn’t have access to this roof but I have learned what I needed to by understanding what I did see.

Now what if a resident had taken a broom and smashed off this “icicle” stalactite? I may not have recognized it so readily. You can be sure that any overhead cracks in concrete are going to be closely examined for this type of mineral deposit.

The old geologists mnemonic; “Mites (stalagmites) go up and tites (stalactites) go down.”

 

Original blog post on ActiveRain: Link to Blog Post

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“Up She Comes”, Regional Difference – Climate Factor

 

Climate difference does mean different construction details. A North Carolina inspector showed me the following diagram of foundation details. We were discussing differences and water problems that crawlspaces have.

The construction shown would not be built for Canadian climates but is OK for North Carolina which is a significantly different climate. The discussion describes what happens in Canadian soils and the different details that mitigate the conditions.

 

foundation drwg

Yes, It’s a regional difference because there is a climate difference.

This set up (shown in the diagram) will let water soak into the brick and concrete. When it freezes here (frost depth; down to 4′ below the surface – on average) the water expands, cracks and breaks the concrete block and brick. That’s the freeze thaw cycle. This will destroy the wall a little more each time.

This happens all winter, a three or four-month period is normal. Today for example it was -14 C (Centigrade/Celsius 0= 32 Farenheight) this morning. This evening it was up to -3 C. Some house foundation walls, especially facing south will have gone through the freeze thaw cycle today. The temperature has swung up to melting and back down to hard freeze 3 to 4 times in the last 2 weeks.

Here brick HAS to stop at least 8″ above the ground level. Concrete or cement block then extend to a minimum of 4′ below grade, to the top of a 12 to 18″ deep concrete footing that MUST rest on undisturbed soil. That’s the minimum; it is usually 6 to 8′ deep. Shallow is more susceptible to freezing effects. Remember the 4′ frost depth quoted is an average. There will be spots or conditions where it is deeper.

When water in the soil freezes it expands and puts pressure on its surroundings.. Downward and laterally the weight of other soil is infinite, pushing back. Upward its a different story, or two or three or more stories depending on the building. This resistance is not infinite so “up she comes”.

This is frost jacking. Frost has been known to lift 7 story structures. So you may have some idea what it can do to a mere house.

Frost heaving is the same thing but this term is more often used to describe landscape displacement.

The footing HAS to be concrete. The foundation wall can be concrete or cement block. BOTH require a waterproofing layer on the outside from ground level down to the bottom of the footing.

Current ‘best building practice’ now installs a drainage plane layer between the exterior waterproofed surface and the ground. This is to let any water present descend. (If there is no water retained against the foundation wall, there will be no seeping or leaking to the interior) The water descends to the weeping tile or French drain at the lower edge of the footing.

This is a belowground landscape drainage system designed to remove all water that is collected. (If no water is allowed to remain in the footing area, no frost jacking can occur.

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 You can see why my comment about the diagramed footing you showed me was “Water runs through it.”

 Crawlspaces and basements between those walls will be wet any time the ground is. They will actually be wetter than the outside ground because that ground is better vented, it doesn’t have a cap on it, the house.

It will be very hard to vent such a crawlspace and what water does get evaporated and removed is constantly replenished from the ground through those walls.

 

In a high humidity summer climate this basement / crawlspace is actually cooler, and condensation can occur. That’s why un-insulated basements are ‘cooler’ in the summer, (and musty smelling.)

 Hence, “Ventilation is futile”

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 “If the last instalment on your grandmothers’ funeral isn’t paid, up she comes”

 

 

 

Original blog post on ActiveRain: Link to Blog Post