Sydney Based + National Delivery
Sydney Based + National Delivery
A wall is injected to specification. Full capillary saturation, correct spacing, correct volume. Six months later the client calls and says the damp course failed.
In most of those callbacks it did not fail. The wall is holding salt, and no damp course can dry a wall that is pulling moisture out of the air.
This page covers how to identify that condition before you quote, so you are not carrying the cost of it afterwards.
A chemical damp course stops capillary moisture rising from the ground, permanently. It does nothing else.
It has no effect on moisture the wall is drawing from the air.
Certain salts absorb atmospheric moisture and hold it. A wall carrying enough of them reads wet on a meter indefinitely, in dry weather, with a perfect barrier below. The moisture is not coming from the ground, so the barrier is irrelevant to it.
Those salts were deposited over decades by the same rising moisture you have just stopped. Water evaporated out of the wall face. The salt did not. Stopping the water does not remove what the water left behind.
Every salt has a relative humidity above which it stops being a dry crystal and becomes a solution. Below that figure it is inert. Above it, it absorbs moisture from the air continuously.
Sydney interiors sit between roughly 55% and 75% RH (Relative Humidity) for most of the year.
Deliquescence relative humidity at 20 °C. Below the listed figure a salt is a dry crystal. Above it, the salt absorbs atmospheric moisture and holds it in solution. Australian interiors typically sit between 55% and 75% RH.
| Salt | Deliquescence RH, 20 °C | Behaviour in an Australian interior |
|---|---|---|
| Calcium chloride | 29% | Never dries |
| Magnesium chloride | 33% | Never dries |
| Calcium nitrate | 51% | Wet almost year round |
| Magnesium nitrate | 54% | Wet most of the year |
| Sodium nitrate | 74% | Cycles seasonally |
| Sodium chloride | 75% | Borderline, usually dry inside |
| Potassium chloride | 85% | Usually dry |
| Sodium sulfate | 87% | Usually dry crystal |
| Magnesium sulfate | 90% | Usually dry crystal |
| Calcium sulfate | 99% | Effectively non-hygroscopic |
Shaded rows fall below the upper limit of normal indoor humidity and are therefore in solution for part or all of the year.
Mixed salt systems deliquesce below the threshold of any single component, so field walls behave slightly worse than the figures above.
Calcium nitrate produces most salt callbacks. Its threshold sits below normal indoor humidity, so it stays in solution essentially all the time. Nothing installed below it changes that.
Mixed salt systems deliquesce below the threshold of any single component, so field walls behave slightly worse than this table predicts. Read it as a best case.
The injected silicone system does not convert water or block moisture mechanically.
Instead, it alters water behaviour by:
Water vapour can still pass through the wall.
When correctly dosed and distributed:
Continuity depends on correct drilling, spacing, and saturation.
Chemical bonding occurs only where the fluid reaches.
Insufficient saturation leads to:
Correct volume and distribution are critical.
Correct establishment of the Capillary Saturation Zone™ at all injection points is the field confirmation that sufficient volume and distribution have been achieved.
Hygroscopic salts do not prevent chemical bonding, but they:
Salt-affected plaster and mortar should be removed where required to avoid misleading post-treatment symptoms.