Does a vertical garden cause dampness?

Not if the water is planned. The plants need water, so the question is where that water goes after the roots have had what they need.

Trouble starts when water sits against the wall for long periods. That happens with a leaking line, a blocked drain, or overflow that runs down the wall face.

Every Greenwall wall is a modular pot system. The soil sits in separate pots held in a frame. The frame is fixed to the wall or stands in front of it.

On walls from ₹750 per sq ft, a drip line runs along each row of pots and a timer controls it. Water that the pots don't hold has to go somewhere, so we plan a drain point for it.

We check three things on the site visit: a water point, somewhere for excess water to drain, and a power point for the timer. See how irrigation works.

• Existing damp. Patches, peeling paint or salt marks mean the wall already takes in water. Find and fix the cause first.
• The wall behind. Ask your contractor whether an outside wall needs waterproofing before anything is fixed to it.
• Wiring and pipes. Know what runs inside the wall before anyone drills it.
• The drain. Know where excess water will end up: a floor trap, a drain or a planter.
• Floors. Indoors, plan how the floor under the wall stays dry.

Leaks are easiest to stop when they're small. Under an annual maintenance contract, each monthly visit includes an irrigation check.

Between visits, look for water marks on the wall, a wet floor, or pots that stay soggy. Tell us straight away if you see any.