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Retrofit indirect lighting – 18 mm is enough

Three ways to get indirect light into a finished home without plasterboard work: DECO surface profile, INDIRECT-1 wall profile and a light moulding behind a timber trim.

Janne Halttu · LedStore.fi · 23.9.2026

Starting point

The room is finished. The ceiling is closed. The electrics are in the walls, not the ceiling. None of this can be changed without significant demolition.

Installing a surface profile on a finished surface. A mounting plate is screwed to the finished surface and the profile clips onto it. The cable runs in a surface-mounted duct to the driver – no building work, no painting.

You can still get indirect light afterwards – but the choice has to be made with open eyes. Every retrofit solution is a compromise between space required, light quality and amount of work.

Three solutions – choose by space required

Solution A: DECO surface profile at the wall-ceiling junction – 29 mm

Retrofit with a profile at the wall-ceiling junction. Light upwards towards the ceiling. No demolition.

How it works: The DECO profile is screwed to the ceiling or wall at the wall-ceiling junction – into concrete, plasterboard or timber. The profile also covers the curtain track, so one product solves both hiding the track and the lighting. LED strip into the profile, cable inside the profile and out at the end. Runs from a socket via the driver, controlled wirelessly with a push-button.

Space from the wall	29 mm
Max strip width	20 mm
Mounting	Screw fixing, surface-mounted
Electrical work needed	No – a socket is enough
Difficulty	Easy
Light quality	Good

DECO surface profile – technical data

Pitfall: The cabling is the only visible part. If the cable cannot be hidden inside the profile or under a cover strip, it stays visible. Plan the cable route before buying.

Product from LedStore: DECO surface profile for the wall-ceiling junction, 55 × 29 mm →

Solution B: INDIRECT-1 on the wall, 20-30 cm below the ceiling – 18 mm

How it works: The slim INDIRECT-1 profile is screwed to the wall 20-30 cm below the ceiling – not tight to the wall-ceiling junction. The distance is the whole point: the light can open up and spread before it hits the ceiling, so there is no sharp beam on the ceiling but an even reflection. Mounted at the junction, the same profile would make a bright line right at the top edge. Only 18 mm from the wall; the IP44 version also suits bathrooms.

Space from the wall	18 mm
Max strip width	12 mm
Mounting height	20-30 cm below the ceiling
IP rating	IP44 (splash-proof)
Suits bathrooms	Yes
Difficulty	Easy
Light quality	Good

INDIRECT-1 – technical data

Product from LedStore: INDIRECT-1 wall profile, 3000 × 41 × 18 mm →

Solution C: Light moulding / small box – 30-80 mm

How it works: A small box at the wall-ceiling junction built from timber, MDF or a ready-made light moulding. The only way to get indirect light that looks like a real dropped ceiling afterwards without plasterboard work. Needs basic carpentry skills.

Space required	30-80 mm from the ceiling
Building work	Carpentry
Difficulty	Moderate
Looks like	A real dropped ceiling
Light quality	Good-Excellent
Materials	MDF, timber or ready-made moulding

Light moulding – technical data

Tip: Always paint the inside of the box white before installing the strip. The lightest possible surface reflects the most light onto the ceiling.

Electrics in a retrofit

The most common question: where does the power come from?

Solution	Space required	Amount of work	Bathroom	Light quality
DECO surface profile	29 mm	Very little	No	Good
Wall profile IP44	50 mm	Little	Yes	Good
Light moulding / box	30-80 mm	Carpentry	No	Excellent

Option 1: A socket. Driver near a socket, cable inside the profile or under a cover strip. The easiest and quickest. No electrician needed if the socket is already there.

Option 2: Adding a junction box. An electrician adds a supply at the wall-ceiling junction. Neater – no visible cable. Requires an electrician.

Option 3: Wireless dimming. Zigbee driver in a socket + wireless wall button. No cable runs needed. Works well but is an extra device. Zigbee controllers from LedStore →

230 V mains strip must not be fixed to the structure without a cover. A 24 V driver system on a socket is neater and safer in a retrofit.

What it costs

Project	Solution	Materials	DIY installation
One wall ~4 m	Z-profile	€80-150	2-3 h
Living room ~14 m	Wall profile	€200-400	4-6 h
Living room ~14 m	Light moulding	€300-600	8-14 h

Products for retrofit → LedStore

Frequently asked – retrofit

Can I do a retrofit myself?

A Z-profile and wall profile are easy without professional help – a drill, screws and a socket are enough. A light moulding needs basic carpentry skills. Electrical installation must not be done yourself.

Is a retrofit suitable for a rented flat?

A Z-profile and wall profile leave only screw holes. They can be removed and the holes are easy to fill. Check your tenancy agreement and ask the landlord if needed.

What is the smallest possible space required?

The DECO profile takes 29 mm and INDIRECT-1 only 18 mm from the wall. With less space, the only option is a very thin light moulding or a furniture light strip mounted directly on the wall, for example under a shelf.

How is the cabling kept invisible?

Inside the Z-profile the cable runs hidden. The short cable from the socket to the profile is covered with a cable strip or wall duct. A white strip, or one matching the wall colour, blends in best.

Which profile type for a bathroom?

An IP44-rated wall profile. Standard profiles are not suitable for damp rooms. The strip must also be at least IP44. Damp-room LED strips from LedStore →

Is 40 mm the absolute minimum?

With DECO and INDIRECT-1 profiles, yes. A low furniture light strip or thin wall moulding can be mounted closer to the ceiling, but the light then comes almost directly and does not spread evenly onto the ceiling. The result is more a line of light than indirect general lighting.

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