Quick answer: Milled screed underfloor heating, also widely marketed in the UK as in-cut or chase-cut UFH, uses a diamond-bladed milling machine to cut shallow channels directly into an existing solid concrete or screed floor. A continuous 16mm pipe is pressed into the channels and the original flooring goes straight back down, with zero increase in floor height, even for a full wet (hydronic) system. It only works on solid concrete or screed floors with enough depth to mill into safely (roughly 75–100mm of combined slab and screed), not on suspended timber floors or thin, damaged or damp slabs. No UK provider publishes a per-square-metre rate; all quote on a project basis after a site survey. Research retrofit options at underfloorheating.info and find specialist installers through the Underfloor Heating Directory.
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What is milled screed underfloor heating?
Milled screed underfloor heating solves the problem that puts most homeowners off retrofitting a wet (hydronic) system: floor height. You'll also see it marketed in the UK as in-cut or chase-cut UFH. Standard retrofit options add a layer on top of the existing floor (a low-profile overlay, typically 15–25mm) or replace it with a new thin screed.
Milling avoids both. It's genuinely underfloor heating without screed. The installer cuts into the slab that's already there, embeds the pipe flush with the surface, then puts the original floor finish straight back down.
Installers use several names for the method: "in-cut," "chase-cutting," "floor milling," "grooving," or "routing". They all mean the same thing. It's a genuine third retrofit option for wet UFH, alongside overlay systems and between-joist installation on timber floors.
How the process works
Whichever provider you choose, the process is broadly the same:
- Strip the existing floor covering. Carpet, tiles, laminate or vinyl is removed to expose the bare concrete or screed.
- Survey and design the pipe layout. The installer maps out the channel pattern for the room, working around fixed features and any known services in the floor.
- Mill the channels. A high-torque, depth-controlled milling machine (JK Floorheating uses its own "Floor-grinder"; other providers use similar diamond-bladed equipment) cuts shallow, evenly spaced grooves into the slab. The machine's integrated vacuum extraction keeps the process close to dust-free, which is what makes it practical to do this in an occupied home rather than requiring a full strip-out.
- Press-fit the pipe. A single continuous run of 16mm pipe is pressed into the milled channels, one unbroken length per loop, with no joints hidden under the floor.
- Pressure-test the loop. As with any wet system, the pipework is pressure-tested before anything is covered, to rule out leaks.
- Refit the flooring. Because there's no new screed to pour, there's no screed curing time. Some providers (incut.co.uk, for example) apply a thin latex levelling compound over the milled channels to bring the surface back flat and smooth before flooring goes back down, distinct from a full screed pour, so it doesn't reintroduce a long curing wait. Providers commonly quote 1–2 days to complete a room, with the system ready for commissioning almost immediately afterwards.
That last point matters. A standard wet retrofit with a new screed layer needs time to cure before the flooring goes down, and you then have to bring the system up to temperature gradually. Milling skips that wait entirely.
Where it works, and where it doesn't
Milled screed UFH only works with concrete or screed. That's how you can install underfloor heating on a concrete floor without raising it. Our full guide to UFH on existing concrete floors compares it with overlay and electric options.
It won't work on suspended timber floors. For those, between-joist retrofit systems remain the zero-build-up route.
Suitable for:
- Solid concrete ground-floor slabs (the majority of UK homes built from the 1930s onwards)
- Existing screeded floors, including screeded extensions
- Rooms where floor height, door clearances or step-free thresholds rule out an overlay system
Not suitable for:
- Suspended timber floors
- Slabs that are thin, structurally compromised, or don't leave enough depth to mill safely, providers generally look for around 75–100mm of combined concrete and screed depth
- Floors with excessively high moisture levels
- Contaminated or unstable subfloors
The machine cuts into the slab, so the installer needs to confirm there's nothing critical in the way before milling starts. That includes existing pipework, cabling or underfloor voids. It's why every provider insists on a site visit and project drawings before quoting instead of pricing the job over the phone.
Floor-finish compatibility over a milled slab is the same as for any polished screed or concrete floor: see our flooring guide's concrete/screed row (27–29°C max surface temperature, virtually zero TOG) for finishing options, or our screed guide if you're weighing a milled retrofit against pouring a conventional new screed over the same room.
Planning a milled retrofit: manifold, zoning, pipe spacing and heat pumps
Milling changes how the pipe sits in the floor. It doesn't change the rest of the system design. Here's what that means for the usual planning decisions.
Manifold placement
A milled retrofit doesn't change manifold planning. You still need a wall-mounted cabinet with the standard clearances: 500–1000mm off the floor, 300mm above for actuators, 150mm below for pipe bends, 200mm either side for access, and 500mm in front for working space. Ideally, keep it within 5–10m of the rooms it serves.
In my experience, using an existing understairs or utility cupboard is usually the cheapest option. It works the same way whether the pipe sits in a milled channel or under a poured screed.
Zoning and circuit layout
Zoning works the same way on a milled system as on any wet UFH install. Each room or area gets its own loop back to the manifold, typically 3–5 zones for a 4-bedroom house (living areas, sleeping areas, bathrooms, and optionally a home office).
There is one useful difference. Our zoning guide frames retrofit zoning around an 18–25mm overlay build-up, while a milled system adds genuinely zero floor height. That can make life easier when the existing rooms sit at slightly different floor levels.
Pipe spacing choice
Milled channels are cut to whatever spacing the design calls for, the same spacing choices used across any wet UFH system, sized with our pipe spacing calculator:
- 100mm (~10m of pipe per m², 75–110 W/m²), conservatories, draughty rooms, high heat loss
- 150mm (~6.67m per m², 60–85 W/m²), well-insulated homes, bathrooms, and the go-to spacing for heat pumps; also the most common spacing used across the UK
- 200mm (~5m per m², 45–65 W/m²), new builds and well-insulated rooms, typically paired with a standard gas or oil boiler running at 45–50°C
As with any wet system, tighter spacing (100–150mm) is usually milled at external-wall perimeter zones, widening to 150–200mm towards the room centre. See our pipe-per-m² guide for the full breakdown, the maximum single-loop length for 16mm pipe, the size used in milled installs, is around 100 metres.
Heat pump compatibility
No UK provider publishes heat-pump performance data measured specifically for milled installs, so treat this as informed reasoning, not a proven figure. Our heat pump guide shows that closer pipe spacing improves COP because the system can deliver the same heat output at a lower flow temperature. Less thermal mass sits between the pipe and the room.
A milled system takes that principle further. The pipe sits almost at the surface instead of being buried in 45–75mm of screed, so it could support an even lower flow temperature for a given output. The site's existing spacing and flow-temperature figures support that expectation, but no milling provider has published or measured it. If you're pairing a milled retrofit with a heat pump, ask for a heat-loss-based design. Don't assume a milled floor automatically outperforms a screeded one.
Milled screed vs other retrofit methods
This is what a conventional full-buildup wet UFH floor looks like in cross-section: flooring, screed, pipe, insulation, then the subfloor. Milled screed goes straight from flooring to pipe, cut directly into the existing slab. That's where the height saving comes from.
| Retrofit method | Floor build-up | System type | Screed curing wait | Best suited to |
|---|---|---|---|---|
| Milled screed / in-cut | 0mm | Wet only | None, ready almost immediately | Solid concrete/screed floors where height is the deciding factor |
| Low-profile overlay | 15–25mm | Wet | Minimal (thin self-levelling layer) | Concrete or timber floors with some height to spare |
| Between-joist | 0mm above deck | Wet | None | Suspended timber floors only |
| Full screed replacement | 45–75mm (see our screed guide) | Wet | Days to weeks | New builds, extensions, or floors already being dug up |
| Electric mat/loose wire | 1.8–6mm | Electric | None | Single rooms, bathrooms, any subfloor type |
So what's the real benefit? Our main retrofit guide sets out the usual hard choice: electric UFH is thin but more expensive to run, while wet UFH is cheaper to run but traditionally adds height.
Milled screed closes that gap on concrete and screed floors. You keep the running-cost advantage of a wet system without the floor-height penalty. It doesn't help with a suspended timber floor, though. There, between-joist installation is still the zero-build-up answer.
Pros and cons
Advantages:
- Zero floor build-up for a genuine wet system, no threshold, door or skirting adjustments needed
- No screed curing wait, so rooms can often be back in use within a day or two of milling
- Faster heat response than a full-screed system, because the pipe sits close to the surface rather than buried in 45–75mm of screed
- A single continuous pipe run per loop, with no in-floor joints to fail
- Dust-controlled installation, thanks to vacuum-extracted milling equipment, making it more practical in an occupied, furnished home than a full screed replacement
Disadvantages:
- Concrete/screed floors only, not an option for suspended timber
- Needs adequate slab depth, so very thin or already-compromised floors may not qualify without further investigation
- Requires a site survey before any quote, there's no standard published rate, so budgeting takes an extra step compared with an overlay system
- Professional-only at every stage, not just DIY-adjacent, unlike DIY-possible electric mats or surface-laid wet pipe, the milling equipment, channel depth control and pipe-pressing process are proprietary to each specialist provider, and a mistake cuts into a structural slab rather than just failing a pipe clip
Cost
None of the UK providers I researched for this guide publishes a standard price per square metre. Every quote follows a site survey and project drawings because the room count, slab condition and depth, pipe layout, manifold and controls all affect the price.
Some providers, including Outsourced Energy, offer an online calculator for a rough indication on simple, small projects. Once a job covers more than a couple of rooms, they move to bespoke, in-house pricing.
If you're budgeting, compare milled screed with wet retrofit overlay systems. Don't assume it's automatically cheaper or more expensive. The fair comparison includes the labour and disruption you avoid by not raising the floor, not just the milling cost on its own.
I'd get quotes from more than one specialist and ask each one to itemise the manifold, thermostats and making-good work separately from the milling and pipework.
Who installs it in the UK
Milled screed / in-cut underfloor heating is offered by a small number of UK specialists, each with their own branded process and milling equipment. You can compare these and other vetted installers on the Underfloor Heating Directory's milled underfloor heating page:
- JK Floorheating. Dutch-founded, over 30 years in the trade, operating from several UK depots, using their own "Floor-grinder" milling equipment and branded Flextube pipe.
- Outsourced Energy. Devon-based, brands the method "IN-CUT," and publishes an online project cost calculator for smaller jobs.
- Channel Heat Systems and Heatflow Installations, both offer floor milling as a dedicated retrofit service alongside conventional wet UFH installation.
- incut.co.uk, a Dorset-based specialist operating from Blandford Forum, milling channels into the existing floor and finishing with a latex levelling compound before flooring goes back down, using a dust-free vacuum extraction system.
View more milled/in-cut UFH installers →
This isn't an exhaustive list, and I'm not recommending one provider over another. Compare quotes from multiple specialists before deciding, as you would for any specialist installation.
Frequently Asked Questions (FAQs)
Does milled screed underfloor heating work with electric systems?
No. It's a wet (hydronic) technique, the milled channels are sized for water pipe, not electric heating cable or mat. If you want a zero-build-up electric option, thin loose-wire or mat systems already add very little height (as little as 1.8mm) without needing to mill the floor at all.
Can milling be used on a floor that already has underfloor heating installed?
Providers assess this case by case. They need to know exactly where the existing pipework or cabling sits before milling anywhere near it. That's what the site survey should establish, so don't assume it's possible without one.
How long does milled screed installation take?
Providers commonly quote around 1–2 days per room for the milling and pipe installation itself, with commissioning following shortly after, much faster than a full screed replacement, which needs days to weeks of curing time before flooring can go back down.
Is milled screed cheaper than an overlay retrofit system?
There's no published rate for either method that allows a fair like-for-like comparison. Both need a site survey. Milling avoids the labour and disruption of raising floor levels (adjusting doors, thresholds and skirting), which can offset its specialist installation cost. Get quotes for both approaches on your project before deciding.
Can you have underfloor heating without screed?
Yes. That's the defining feature of milled screed (in-cut) underfloor heating. The installer mills the pipe directly into the existing concrete or screed slab, so there's no new screed to pour or cure. It's the only way to get a full wet UFH system with genuinely zero floor build-up on a concrete or screed subfloor.
Do you have to dig up the floor for milled underfloor heating?
No, that's the whole point of the method. The existing floor covering (carpet, tiles, laminate) is removed, but the slab itself is milled, not excavated or broken up. That's a key difference from a full screed replacement, which does involve breaking out the existing floor down to a level where a new screed can be poured.
What machine is used to cut underfloor heating into concrete?
A high-torque, depth-controlled milling machine with an integrated vacuum extraction system, sometimes called a concrete router or concrete milling machine. JK Floorheating uses its own branded "Floor-grinder"; other UK providers use similar diamond-bladed equipment. The vacuum extraction is what keeps the process close to dust-free, making it practical in an occupied, furnished home.
Do you need insulation under a milled underfloor heating system?
No new insulation layer is added as part of the milling process itself, the pipe is milled straight into the existing slab, unlike an overlay retrofit, which typically builds in an insulation layer as part of its board or panel system. Whether the existing slab already has adequate insulation below it (common in newer builds, less certain in older properties) is exactly the kind of thing a pre-milling site survey should establish.
Does a milled system store heat as well as a full screed floor?
No. This is a genuine trade-off. A full sand/cement screed (65–75mm) acts as a thermal store, holding enough heat to keep a room warm for 2–3 hours after the system switches off. A milled system doesn't have that extra thermal mass, so it heats up faster but also cools sooner.
Neither is automatically better. You're trading the screed's heat retention for lower floor height and faster installation, so choose the one that fits your priorities.
Next steps
Want the full picture? Start with our complete guide to retrofitting underfloor heating, which covers low-profile overlay and between-joist systems for timber floors. Our guide to UFH on existing concrete floors compares milling, overlay and electric mats side by side, including costs.
If floor height isn't a problem, compare milled screed with a standard wet UFH installation on cost and running efficiency before you commit to a specialist milling provider.
Considering a milled retrofit? Compare quotes from specialist installers via the Underfloor Heating Directory.
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