Question one: where does rain go
An outdoor screen is a vertical plane with a horizontal top edge. Water lands on the top, runs down the face, and collects at the bottom. If the bottom edge sits on a concrete plinth with no slope, that water sits against the cabinet. Design a 2 percent fall away from the screen and a drainage channel, or plan for a stainless bottom trim that can be removed and cleaned.
Question two: what is under the paving
A 30 square metre screen with a steel frame is roughly 2.5 tonnes. That is not a lot for a proper foundation, but it is too much for paving slabs on sand. We ask for a core sample or the original site plan. If neither exists, we ask for a 300 mm deep test pit at each corner.
Question three: is the base inside or outside the flood line
In coastal cities, a screen on a low plinth can sit in 100 mm of water during a storm. The cabinet is sealed, but the power supply compartment is usually at the bottom. Raise the power compartment to 400 mm above finished ground, or put it in a separate enclosure away from the base.
Question four: wind direction on the actual site
Design wind pressure is calculated for the worst case, but the fixings see a different pattern if the screen is in a corner between two buildings. A corner site creates a vortex that loads the frame from behind. We ask for a photo of the site from four directions and a note on what is upwind.
What the foundation drawing should contain
- Concrete grade and reinforcement, not just dimensions.
- Anchor type and embedment depth.
- Drainage fall and outlet location.
- Cable entry height above finished ground.
- Earthing point and resistance target.
One cost note
A proper foundation is typically 8 to 12 percent of the screen cost. A foundation that has to be redone after the first rainy season costs three times that, plus the screen downtime.