Kitchen Chimney Installation: Getting the Hole Right

A kitchen chimney exhaust hole needs to be sized to the duct collar, not the chimney unit itself, which for most Indian modular kitchen chimneys means a 150mm (6 inch) core cut through the wall, positioned directly behind or slightly above the chimney's rear outlet, and sloped a few degrees downward toward the outside. Getting any one of these three things wrong, size, position or slope, is why a surprising number of new chimneys leak smoke into the kitchen, drip grease-laden condensation back inside, or rattle from a duct that is bent too sharply to fit the hole.

This job looks simple and often gets treated as an afterthought during a modular kitchen fit-out, squeezed in after the carpentry is finalised. That is exactly backwards. The hole position should be decided before the kitchen unit layout is finalised, not after, because the duct run length and number of bends directly affect how well the chimney extracts.

We do this cut regularly across Gurugram kitchens, from compact flats near Cyber Hub to larger independent house kitchens in Sector 56, and the same three mistakes come up on nearly every retrofit job we are called to fix.

Sizing the hole correctly

Most Indian chimney brands use a 6 inch (150mm) round duct collar, though some higher-capacity or European-import units use 200mm. Always check the chimney's installation manual or the collar itself rather than assuming, since cutting undersized forces the duct to compress at a bend, which measurably reduces suction efficiency, while cutting oversized leaves a gap that needs extra sealing and looks unfinished from outside.

Positioning the hole

The ideal position is the shortest, straightest possible run from the chimney's outlet collar to the outside wall, ideally with zero or one bend. Every additional 90-degree bend in the ducting reduces exhaust efficiency meaningfully, which is a well documented issue in general HVAC and kitchen ventilation practice; see the general principles on Wikipedia's page on range hoods for background on why straight duct runs matter. In a typical Indian kitchen layout, this usually means cutting the hole directly on the wall behind the hob, roughly 200-250mm below the ceiling, rather than routing the duct sideways through the cabinet run to an unrelated wall.

• Measure from the finalised chimney unit position, not from the empty wall before cabinetry is installed.
• Keep the duct run under 2-2.5 metres with a maximum of one bend wherever the kitchen layout allows.
• Avoid positioning the hole directly above a window or ventilator on the same external wall, which looks messy and can affect natural light framing.
• Check the wall thickness and construction, since brick, AAC block and RCC each cut slightly differently and affect how quickly the job goes.

Getting the slope right

The hole should slope downward from inside to outside by a small angle, roughly 3-5 degrees, so that grease-laden condensation drains outward under gravity instead of collecting in the duct and dripping back into the kitchen. This is a small detail that is very easy to get right during cutting and very difficult to fix afterward, since correcting the slope on a finished hole usually means re-cutting it larger and packing the gap unevenly, which looks poor and rarely seals as well.

Every chimney call-back we get for grease dripping down the wall traces back to a hole that was cut flat or, worse, sloped slightly the wrong way.

Wall type considerations

External kitchen walls in Gurugram apartments are usually RCC or solid block, both of which need a proper diamond core drill for a clean round hole, described in more general terms in our chimney and exhaust hole cutting guide. Attempting this with a hammer drill and chisel, which some cheaper fit-out teams still do, leaves a ragged, oversized opening that is hard to seal neatly and often chips the exterior finish visible from outside the building.

If your kitchen sits on an internal wall with no direct external face, for example in some older independent house layouts, the duct has to be routed to the nearest external wall or false ceiling void, which changes both the cutting plan and the recommended chimney capacity, since a longer duct run needs a chimney rated for higher static pressure. This is worth checking with your chimney supplier before committing to a hole position.

Sequence for a smooth installation

1. 1Confirm the exact chimney model and duct collar size before ordering cabinetry.
2. 2Mark the hole position based on final chimney placement, not tentative kitchen drawings.
3. 3Cut the core with the correct slight downward slope toward outside.
4. 4Fit the duct with minimal bends and seal both ends with weatherproof sealant.
5. 5Fit an external cowl or louvre to keep rain and birds out of the duct opening.
6. 6Test the chimney at full speed before the kitchen platform and backsplash are finished, so any adjustment is still easy to make.

External cowl and finishing

Do not leave the outside end of the duct as a bare hole. A proper external cowl or louvred cover keeps rain, dust and birds out, and most housing societies in Gurugram, particularly in maintained complexes around Golf Course Road and DLF Phases, expect a neat exterior finish rather than a visible pipe stub for aesthetic and facade maintenance reasons. This is a small additional cost that avoids both a maintenance complaint and water ingress during monsoon.

Typical costs

A single chimney exhaust core cut through a standard RCC or block external wall typically falls in the range of ₹1,200 to ₹2,500 depending on wall thickness and floor level access, a typical range, confirm on quote. Adding an external cowl and interior trim ring is a modest extra. This is a small fraction of the overall modular kitchen budget and not a place to cut corners.

Book the hole before the kitchen units arrive

The best time to get this cut done is before your modular kitchen units are installed, once the chimney model and final layout are confirmed. If you are planning a kitchen fit-out anywhere in Gurugram and need the exhaust hole cut to the correct size, position and slope, contact us with your chimney model and kitchen layout and we will handle it in one visit alongside any other openings your renovation needs, see our full services list for related work.