In-Floor Heating for Concrete Slab Floors

Yes — but the approach is different from new construction. You cannot embed cables into an existing cured slab, so there are two practical options for adding radiant heat to an existing concrete floor:

Option 1: Above-Slab Installation (Most Common)

Electric heating cables or mats are installed on top of the existing concrete slab, embedded in a thin layer of self-leveling underlayment or mortar before the finish floor is applied. This adds approximately ¼ to ½ inch to the floor height.

• Works under tile, stone, LVP, laminate, and engineered hardwood
• WarmlyYours TempZone™ Cable is ideal for this approach — it can be laid at custom spacing over any concrete surface
• An uncoupling membrane (such as Prodeso) can be used as the installation bed, adding crack isolation benefits

Option 2: Floating Floor System

A floating floor system with built-in heating (such as WarmlyYours Environ™ Flex Roll) can be installed over concrete without any mortar or self-leveling compound — ideal for renovation projects where minimal height gain is important.

Important: Insulate from Below

Existing slabs on grade often lack insulation beneath them. While you can't add under-slab insulation retroactively, using a thermal underlayment on top of the slab (such as WarmlyYours ThermalSheet) helps direct heat upward rather than losing it into the concrete mass.

Get a free SmartPlan™ or Instant Quote to find the best solution for your existing slab.

WarmlyYours makes it easy to get started with in-slab concrete floor heating — whether you want a quick price estimate or a full professional installation layout.

Option 1: Instant Quote

Use the WarmlyYours Instant Quote tool to get product recommendations and pricing in minutes. Simply enter your room dimensions and the tool will calculate the right cable size, coverage, and cost for your slab.

Option 2: Free SmartPlan™

For a complete, engineer-drawn installation layout, submit your floor plan for a free SmartPlan™. Our team will:

• Design the exact cable layout for your slab dimensions and shape
• Specify cable spacing and wattage per square foot
• Identify the optimal thermostat location and cold lead routing
• Provide a complete materials list

The SmartPlan™ is provided at no charge and is ideal for contractors, builders, and homeowners planning new construction or a slab addition.

Talk to an Expert

Prefer to speak with someone? WarmlyYours has a team of radiant heating experts available 24/7 to answer questions about your in-slab project. Visit the in-slab concrete floor heating page to get started.

Installing electric radiant heating in a concrete slab is done during the construction or renovation process, before the concrete is poured. Here is a step-by-step overview:

1. Prepare the subbase: Ensure the ground is properly compacted and a vapor barrier is in place. Add rigid foam insulation beneath the slab to prevent heat loss downward into the ground — this is critical for efficiency.
2. Lay rebar or wire mesh: The heating cable will be tied to this grid to hold it in position during the pour.
3. Install the heating cable: WarmlyYours electric heating cable is laid out in parallel runs at a consistent spacing (typically 3–4 inches apart for primary heat, wider for supplemental). Never cross or overlap cables.
4. Connect the cold leads: The non-heating lead wires are routed to the wall where the thermostat will be mounted.
5. Test the cable resistance: Before pouring, verify the cable resistance with a multimeter to confirm no damage has occurred. Record the reading.
6. Pour the concrete: The slab is poured carefully over the cables. Avoid dragging equipment directly over the cables.
7. Install the thermostat: Once the slab has cured (typically 28 days), connect the system to a WarmlyYours thermostat and commission the system.

Get a Custom Installation Plan

WarmlyYours provides a free SmartPlan™ — a professional layout drawn by our engineers showing exact cable placement, spacing, and wattage for your specific slab. You can also get an Instant Quote online in minutes.

In-slab radiant floor heating is highly efficient when properly designed and insulated — but it works differently from other heating systems, and understanding those differences is key to maximizing efficiency.

Why It's Efficient

• Thermal mass advantage: Concrete stores heat and releases it slowly and evenly, meaning the system doesn't need to run constantly — it heats the slab, then the slab radiates warmth for hours after the system cycles off.
• No heat loss through ducts: Unlike forced-air systems, there are no ducts to lose heat through — 100% of the energy goes into the floor.
• Lower thermostat settings: Radiant heat warms people and objects directly, so rooms feel comfortable at lower air temperatures — typically 2–4°F lower than forced air, reducing energy use.
• Zone control: Each room or zone can be controlled independently, so you only heat the spaces you're using.

The Importance of Under-Slab Insulation

The single biggest factor in in-slab efficiency is insulating beneath the slab. Without it, a significant portion of heat is lost downward into the ground. Rigid foam insulation (minimum R-10) under the slab is strongly recommended for all in-slab heating projects.

Estimate Your Operating Costs

Use the free WarmlyYours Energy Use Calculator to estimate daily and annual operating costs based on your slab size, local electricity rate, and usage schedule. You can also use the Heat Loss Calculator to determine if in-slab heating can serve as your primary heat source.

Ready to get started? Get an Instant Quote or request a free SmartPlan™.

A heated concrete slab is compatible with most hard flooring types. Here's what works well and what to avoid:

• ✅ Tile & Stone — The best choice for a heated slab. Excellent heat conductor, highly durable, and completely unaffected by the temperature cycling of radiant heat.
• ✅ Polished or Stained Concrete — The slab itself becomes the finish floor — no additional flooring needed. Very popular in modern and industrial interiors.
• ✅ Luxury Vinyl Plank (LVP) — Works well over heated slabs; ensure the product is rated for use with radiant heat and has a combined tog rating of 1.0 or less.
• ✅ Engineered Hardwood — Compatible; the dimensional stability of engineered wood handles the mild temperature changes of a slab system well.
• ✅ Laminate — Compatible when rated for underfloor heating; keep slab temperatures below 85°F (29°C).
• ⚠️ Solid Hardwood — Use with caution; the slow, even heat of a slab system is gentler than other radiant types, but solid hardwood can still expand and contract. Consult your flooring manufacturer.
• ❌ Thick carpet with high tog underlayment — Not recommended; insulates the slab too heavily and significantly reduces heating efficiency.

Key Rule: Keep Slab Surface Temperature Below 85°F (29°C)

Most flooring manufacturers require the floor surface temperature to stay at or below 85°F (29°C). A floor-sensing thermostat — included with all WarmlyYours systems — monitors and maintains this automatically.

Not sure which system is right for your flooring type? Request a free SmartPlan™ or get an Instant Quote and our team will guide you.

In-slab radiant floor heating is an electric heating system where heating cables are embedded directly inside a concrete slab before it is poured. The cables become a permanent part of the slab, which then acts as a large thermal mass — absorbing heat and radiating it evenly upward into the room.

How It Works

1. Electric heating cables are laid out and secured to rebar or a wire mesh grid on top of the subbase
2. Concrete is poured over the cables, fully encasing them
3. Once cured, the slab is connected to a thermostat and powered on
4. The concrete heats up slowly and radiates warmth evenly across the entire floor surface

Key Benefits

• Even, consistent heat: No hot or cold spots — the entire slab surface radiates warmth uniformly
• Invisible system: No visible heating elements, vents, or radiators
• Long-lasting: Cables embedded in concrete are protected from damage and can last the lifetime of the building
• Ideal for new construction: Best installed during the initial pour of a new slab or addition

Not sure where to start? Request a free SmartPlan™ and our engineers will design a custom layout for your slab.