How to plan a terrace garden in Bengaluru

Waterproofing is a separate job. None of the gardeners we work with gave us a waterproofing price, and none of their quotes we hold has a waterproofing line. On one Bengaluru builder's prices it's about ₹40 to ₹60 a sq ft for an acrylic coat, ₹50 to ₹70 for cementitious, ₹80 to ₹120 for PU and ₹90 to ₹130 for a bituminous sheet. One contractor says the cheapest coats, at ₹40 to ₹50, usually last only a year or two, so don't use them under a garden you won't want to move. Crack repair and fixing the slope usually cost extra.

The flood test is also your proof. A leak can show up months later, after the first heavy rain, and then it's hard to say what caused it. A photo of the dry ceiling on the day of the test settles it.

Where the water goes on a terrace garden

Tap a number to see what it is and what it costs.

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1. 1

   The roof's waterproofing

   ₹40 to ₹130 a sq ft

   From a waterproofing contractor, before anything goes on

   Add to my request: The roof's waterproofing
2. 2

   The rain outlet

   Ask

   Keep it clear of soil and leaves, and clear it before the monsoon and after a big storm

   Add to my request: The rain outlet
3. 3

   Grow bags on a stand

   About ₹100 to ₹200 a bag

   Our estimate. Stands: ask. Bags on the floor hold water and block the slope to the outlet

   Add to my request: Grow bags on a stand
4. 4

   A drain layer under the grass

   About ₹50 a sq ft

   One gardener's drain cells at ₹75 each, about two for every three sq ft, with geo cloth. On top of the grass price

   Add to my request: A drain layer under the grass
5. 5

   A shade net on its own frame

   ₹1,500 to ₹3,000

   One seller's price for the net alone. The frame: ask. One that stands on its feet puts no holes in the roof

   Add to my request: A shade net on its own frame

Who pays if the room below leaks? Of the six providers here, one's printed terms leave civil repairs and drainage to the customer: Make Heaven My Garden's. The terms we hold for the other five say nothing about it. So ask, and get the answer in writing before you pay.

Roots. Keep plants in bags, pots or lined planters. A peepal or banyan seedling dropped by a bird can root in a crack in the parapet, so pull it out the day you see it. If you build a soil bed, ask the waterproofing contractor about a root-resistant layer under it.

Keep the water moving. Pots and bags straight on the floor hold water under them and block the slope to the drain, so raise them on stands or bricks. A pergola's posts fixed into the slab make holes in the waterproofing, so ask how they're fixed and who seals round them. Keep water drums covered and tip out saucers: the Karnataka High Court has told BBMP to fine homes and societies that leave water standing.

The code's figure is the least a designer must allow. A terrace built as a sit-out or for gatherings is designed for about 200 to 300 kg a square metre. What your slab was built for is on its structural drawings, and only an engineer can say. Rain isn't in these figures, and wet soil weighs more than dry.

The mix decides the weight. A drum of soil weighs about 50 kg, and a drum of cocopeat and sludge mix about 15, by one Bengaluru gardener's count. A light mix dries faster, so it needs more water.

A bed is a load in one place, like the soil bed in the chart. Ask the engineer where the heavy pieces should stand.

Start with whoever built the house. Their engineer or contractor may still have the structural drawings. In a flat, ask the builder or the association.

Only an engineer can sign off the slab. A terrace builder at the top of the market says there's no blanket limit, and leaves a heavy build to the client's own civil engineer. We found no published fee for a slab check in Bengaluru. If someone at home worries about the roof, the engineer's visit settles it.

Want one contractor for all of it? Ingenium Designs also do the floor, lights, plumbing and painting on a full job.

Check the supplies on a bill. Carrying it all up is often its own line.

A gardener

about ₹40,000 to ₹42,500 before tax, our estimate

A design firm

about ₹68,500 to ₹72,500 before GST, our estimate

Artificial grass at ₹65 a sq ft, then about ₹10,000 of drain cells under it

Artificial grass laid at ₹110 a sq ft, plus about ₹10,000 of drain cells at the gardener's price (their quote has no line for them)

Eight pots with plates at ₹450, size and material not on the quote

Eight 2 ft fibre planter boxes at about ₹2,800

16 plants at ₹325 to ₹475

16 plants, 2 to 4 ft, at ₹500 to ₹600

Red soil and cocopeat, two gardener days at ₹1,800, transport ₹1,350

Potting mix, two days' labour at ₹1,000 to ₹1,200, transport ₹1,000 to ₹2,500

What the extra pays for. About ₹19,000 of it is the planters: eight 2 ft fibre boxes against eight pots with plates, which may be smaller. About ₹9,000 is the grass: the firm's ₹110 includes laying it, and the gardener's ₹65 is the grass alone, with his laying in the two days we counted. The rest is the plants, priced by size on the firm's quote. Neither price includes waterproofing (question 1) or levelling the floor.

Who on mytribe works each way. The gardener's way: Make Heaven My Garden, who lays grass on drain cells and geo cloth, and Greenedeck, who put drainage grids under grass. Ask each how they plant and what it costs. The firm's way: Sqft Farm, who use fibre planter boxes and quote line by line. They take bigger jobs and want several pieces on a terrace, so ask for their smallest job first.

Budgets split in two. Of the eight people who named a budget when they asked mytribe for a terrace garden, four said ₹40,000 or less, for plants, pots and a few vegetables. The other four said ₹2 lakh to ₹6 lakh, and added a roof, a deck or seating. So decide whether you want a garden or a sit-out, and say it on the first call. Question 3 prices both.

For grow bags, a garden firm's fitted kit costs more than a mali. Twenty fitted trays on 80 sq ft are ₹26,998, more than a mali charges for 30 bags (question 3). The extra buys frames and drain cells that keep the wet mix off the roof, a fixed price, the fitting and someone to call. The firm promises nothing about your waterproofing.

A sit-out is building work. A pergola adds weight and its posts go into or onto the slab, so it needs the engineer's look from question 2. A builder who welds and cuts on your site, as Misty Garden Weldscape do, brings noise and needs power and, in a society, its permission and set hours.

A real lawn on a terrace is the hardest thing to keep. It needs a deep bed of wet soil, the heaviest thing you can put up there, and a lot of water through the summer. None of the six providers here quotes one, so every terrace lawn price on this page is artificial grass.

Already have plants? Six of the 38 people who asked mytribe about a terrace wanted to keep theirs. Say how many you have and send photos. PlantPets has reworked a terrace around the plants already there.

What it gives back. About 4 to 6 kg of vegetables from a large pot, for about an hour a day of your time, by one Bellandur resident's count. Grow it for fresh greens and the time up there.

Roses like a sunny terrace. One gardener suggests creeper roses, in planters as big as you can fit and soil that drains well.

If monkeys, squirrels or birds come to your terrace, ask for a net over the beds as its own line in the quote. We found no price for one.

Over a year, upkeep adds up. A mali's weekly visits come to about ₹16,800 to ₹48,000 a year, as much as his grow-bag setup or more.

Watering is the hard part. Pots in full sun dry out fast, and a drip line needs a tap or the tank's line up there. If nobody can go up daily, ask your house help or the building's staff, and agree a fee.

Ask what a visit includes. Ask whether manure, pest spray and replacing a dead plant are in the price. If you're away or abroad, ask for photos after each visit and a bill for anything bought, so you can check the supplies against the prices in question 3.

Water with what you can. When Bengaluru runs short, BWSSB bans using drinking water for gardens, with a ₹5,000 fine. A terrace takes more water than a balcony, so plan for summer.

A shared garden can work. One Bellandur apartment got its association's approval first, and runs a vegetable garden on the common terrace for about ₹15,000 a year on mix, labour, seeds, feed and containers.

Talk to the top floor first. The flats right under a common terrace are the ones that worry, and one leak complaint can close the garden. Do the flood test from question 1 with them, before and after, and keep everything in bags or pots on stands.