Protection against ground moisture
Where the moisture comes from
Section titled “Where the moisture comes from”From the ground
Section titled “From the ground”Capillary rise through the foundation.
From the concrete
Section titled “From the concrete”Fresh concrete gives off moisture for a long time.
From rain
Section titled “From rain”Splashback around the ground connection, snow build-up, poor drainage.
All of them lead to the same place: moisture at the lowest junction of the building, where the structure begins.
Why it is critical with steel
Section titled “Why it is critical with steel”Corrosion of steel requires sustained moisture. In a dry structure the life of a galvanised profile is comparable with that of the building. The base junction is where that condition is most easily broken.
On top of that, the alkalinity of fresh concrete attacks the zinc layer — so it is not enough for it to end up dry: it also has to be separated. Material pairing and corrosion.
The elements of the solution
Section titled “The elements of the solution”Damp-proofing beneath the bottom track
Section titled “Damp-proofing beneath the bottom track”Continuous, across the full width of the track, tied into the adjoining structures.
A raised base level
Section titled “A raised base level”The structure should not begin at ground level: keeping splashback and snow away is simple, cheap protection.
Drainage
Section titled “Drainage”Ground falling away from the building, rainwater led away, land drains where needed.
Ventilation where there is a void
Section titled “Ventilation where there is a void”With a suspended floor, ventilating the space beneath it carries the vapour away.
The pitfalls on site
Section titled “The pitfalls on site”- interrupted damp-proofing at junctions and corners,
- puncture at the fixings, if it is not dealt with,
- later filling of the ground, which removes the protective height,
- building in wet: moisture sealed in cannot get out later.
That last one matters particularly in a light gauge steel wall: whatever is built in has to be lived with for the whole service life of the structure.
The timing of the check
Section titled “The timing of the check”The damp-proofing is under the track — not visible once erection is done. So photograph and record it at installation. The construction log.
The point
Section titled “The point”The life of a steel frame is decided at the base junction. Damp-proofing done well here is worth more than any coating thickness.