In-Screed Underfloor Heating for Wollongong & Illawarra Homes
When a floor is being built or fully rebuilt, the warmest and most durable place to put the heating is inside the floor itself. In-screed and in-slab systems bury a robust heating cable in the sand-and-cement screed or the concrete slab, so the whole floor mass becomes a deep reservoir of heat that climbs gently and stays warm long after the system switches off — ideal for cold Illawarra mornings and open-plan living. Because the cable is cast in during the screed stage, it suits new builds and full bathroom renovations rather than quick tile-only refreshes; it needs to be planned before the floor goes down. This is the in-the-floor corner of our Underfloor Heating range, where we compare the Thermogroup and Radiant cables and kits we stock for South Coast builders and renovators. If your floor is already down and you only need to reheat the tile bed, the faster option is the thin mat covered on the next page.
In-Screed vs Under-Tile — When to Choose In-Screed
The choice comes down to when your floor is being built. In-screed (and its heavier in-slab cousin) is laid before the screed or slab goes down, embedding a thick cable in the floor mass — it is slower to warm but holds heat far longer, making it the efficient choice for whole rooms, new builds and off-peak running where the floor coasts on stored warmth. Under-tile heating is a thin cable bonded to a mat that sits directly under the tiles on an existing sub-floor; it barely raises the floor height and responds fast, so it is the go-to for renovations where the slab stays put — see our Under-Tile Heating Mats. Whichever you pick, the cable itself is not a self-contained appliance: it needs a floor sensor and a thermostat to run safely and economically, so budget for one from our Thermostats & Controllers page. For how a warm floor fits a lower-energy home, read Sustainable Luxury: Eco-Friendly Bathroom Choices, and to see where the screed stage falls in a project, our Renovation Timeline.
Thermogroup Thermoscreed Loose-Wire In-Screed Cable
Thermoscreed is Thermogroup’s loose-wire cable made to be laid straight into a sand-and-cement screed, and it is our lead option for tiled floors going down as part of an Illawarra renovation. The single-ended cable runs at 18 watts per linear metre on a standard 240-volt supply, and at just 5.5 mm thick it disappears into a normal screed bed without lifting your finished floor level. It is spaced across the room by hand and held down with fixing tape, galvanised profile or in-screed mesh (accessories), which lets an experienced fitter tune the cable spacing to the exact heated area and work neatly around vanities and shower bases. A generous 3-metre cold tail reaches back to the wall for the electrician, the cable carries an IP67 rating and a 28°C floor limit, and Thermogroup back it with a lifetime warranty. It is sold as cable only in fixed lengths, so we size the run to your floor and pair it with a thermostat.
Thermogroup Thermoslab In-Slab Heating Cable
Where Thermoscreed heats a screed bed, Thermoslab goes deeper — it is a heavier-gauge cable designed to be cast into the structural concrete slab itself, turning the entire slab into a thermal store. Rated at 30 watts per linear metre on 240 volts, the 7 mm single-ended cable is tied to the reinforcing mesh (cable ties available as an accessory) before the pour, so it is a decision made at the slab stage of a Wollongong new build, not a renovation retrofit. Because the slab holds so much heat, it suits whole-of-home and off-peak running: charge the slab on cheaper overnight tariffs and let it release warmth through the day. It shares the IP67 rating, 28°C floor limit and lifetime warranty of the Thermoscreed cable, with a longer 5-metre cold tail to suit deeper slab terminations. Supplied as cable only in fixed lengths matched to your slab area.
Radiant In-Screed Cable Kit — 30m / 600W
Radiant’s in-screed cable kit is the all-in-one loose-cable option for a mid-sized bathroom or ensuite, packing everything but the thermostat into one box (SKU ISCK600W). It contains a 30-metre heating cable rated 600 watts — an even 200 watts per square metre — plus the wire mesh, cable ties and floor sensor needed to lay it out and bury it in the screed. That output covers a 2.9 to 3.3 m² heated area, so it is well matched to a typical Illawarra bathroom floor once you subtract the vanity and shower footprint. The 7 mm cable runs on a standard 240-volt supply and carries an IPX7 ingress rating for the wet-area environment. Loose cable on a drum lets a skilled fitter thread the run through awkward, non-rectangular rooms, and Radiant back the kit with a 10-year warranty (2 years on the thermostat). Pair it with a Radiant thermostat to control it.
Radiant In-Screed Cable Mat Kit — 3m² / 600W
This Radiant kit (SKU ISCMK200-600W) delivers the same in-screed warmth as the loose-cable kit but with the 7 mm heating cable pre-attached to a mat, so layout is faster and the spacing is even and foolproof. The 500 mm-wide mat is simply rolled out and snaked back and forth to fill the floor — you cut the matting backing only, never the cable — then covered by the screed so your tiler works on a flat, freshly screeded surface with the heating fully hidden. It produces 600 watts across a 3 m² heated area at an even 200 watts per square metre, runs on standard 240 volts, and shares the IPX7 rating and 10-year warranty (2 years on the thermostat) of the loose-cable kit. It is the quicker choice for straightforward rectangular Wollongong bathrooms; if the mat is unavailable, the loose-cable ISCK600W kit above is the direct substitute. Control it with a Radiant thermostat.
Planning Your In-Screed Floor — What Comes Next
In-screed and in-slab heating reward planning: because the cable is cast into the floor, the size, spacing and thermostat all need to be settled before the screed goes down, which is exactly why it belongs in the early design conversation for a new build or full renovation. Get it right and you have a quiet, invisible heat source that warms the whole floor mass and holds that warmth for hours. If your slab is already poured and staying put, the faster route is the thin mat on our Under-Tile Heating Mats page — and every system here, in-screed or under-tile, still needs a sensor and thermostat from Thermostats & Controllers to run safely and economically. Serving builders, tilers and renovators across Wollongong, Unanderra and the wider Illawarra and South Coast — bring your floor plan and screed timeline into the showroom and we will size the cable to your room.
