Short answer: before you ask for a radiant floor heating quote, gather your floor plans, what is under each floor, the floor covering you want in each room and what you know about your heating equipment. Then ask every contractor the same six sets of questions below, starting with who calculates the heat loss of each room. Comparing bids is only fair when they cover the same work.
You do not need to pick a tubing spacing before your first conversation with an installer. Start with the rooms you want to heat, the floors you want to keep and the documents you already have. A homeowner on HeatingHelp put the usual starting point plainly: "What questions should I ask a plumber about Radiant heating?" This page answers that question as a checklist.
Copy the six lists into your notes or print this page. Beside each item write ready, to confirm or not applicable, and the name of whoever will confirm what is missing. You can use the checklist without an account or a HeatAlgo purchase.
This guide covers hydronic radiant floor heating: warm water circulating through tubing in the floor. Electric heating mats are outside its scope. You gather and check the inputs; your contractor reviews the proposed design for your house and the selected system before installation.
1. Floor plans, measurements and fixed features
- A plan for every floor included in the work, with its date or revision.
- Room names, uses, dimensions and ceiling heights.
- At least one measured dimension on each plan so its scale can be checked. Note which dimensions come from drawings and which from site measurements.
- Doors, stairs, kitchen cabinets and island, bathroom fixtures, fireplaces and other fixed features marked on the plan.
- Walls, doorways or layouts that may still change.
Mark the rooms you want heated and the areas to leave alone. Fixed features are points to discuss with the contractor, not a universal rule for where tubing may go. If a drawing no longer matches the house, flag the difference.
2. What is under the floor, the insulation and the height you have
- Whether the floor is a slab on grade, a slab over a basement or crawlspace, or a wood-framed floor over joists, if known.
- Existing layers, insulation material and thickness, backed by drawings, product sheets or photos where you have them.
- What will be kept, removed or rebuilt, and any known moisture or floor-condition problems.
- The height available for the complete new floor, finish included, at doors, stairs, thresholds and adjoining rooms.
- Who will inspect the existing floor and confirm the proposed buildup.
Ask what insulation goes under the slab and at its edges. A contractor who plans to skip it should explain how the heat going down was accounted for, because that is heat the room does not get. Do not choose a system by its advertised panel thickness alone: ask for the full floor buildup and the finished floor height it gives. Leave unknown layers marked to confirm.
Know which kind of system you are being offered. Tubing embedded in a slab or a thin slab is one family. Joist-space, staple-up, plate and panel systems under a wood subfloor are another, with their own output data from the manufacturer. HeatAlgo calculates the first family only and does not calculate joist-space, staple-up, plate or panel systems.
3. Floor coverings and product sheets
- Your preferred covering in each room: tile, engineered wood, solid hardwood, vinyl, carpet or something else.
- The manufacturer, exact product and thickness where already chosen.
- Underlayment and adhesive specifications, where they apply.
- The supplier's statement that the product suits radiant floor heat, its thermal resistance and any temperature limits or installation conditions.
- Rooms where you are still choosing between coverings.
Share the product sheets before the design is final, and ask the contractor to check the covering and the floor's heat output together. Why wood and carpet deliver less heat than tile at the same water temperature is explained in the guide to radiant floor heating water temperature. A label saying "suitable for radiant heat" is still a reason to read that product's conditions.
4. Heating equipment and the room-by-room load
- The existing or planned boiler or heat pump, with model and data sheet if known.
- Rooms that will keep baseboard, radiators or another kind of heat.
- Any room-by-room heat loss calculation, with the building details and assumptions it used.
- Planned changes to insulation, windows, room use or ventilation.
- Who will check the heat each room needs against what the proposed floor can deliver.
Floor area alone does not describe how much heat a room needs. Ask the contractor for their room-by-room load calculation and keep it with the bid. If there is none, say so and ask who will provide it. Do not guess insulation values or pick a water temperature just to fill a blank.
5. Tubing, manifold, supply water temperature and controls
- What tubing is proposed, and whether it is oxygen-barrier PEX. Ask for the product name and size in the bid.
- How the supply water temperature will be controlled: a mixing valve, outdoor reset, or both, and what sets the temperature on a mild day.
- Possible locations for the manifold, the unit that connects the loops, with room for access and service.
- Routes from the manifold to each room, with doorways, level changes and other obstacles marked.
- Rooms you want to control separately, possible thermostat locations and any wiring limits.
Treat your manifold ideas as suggestions until checked. Ask the contractor to include the runs to and from the manifold in each loop's length and to confirm access, connections and controls. Why those runs count is shown in the guide to tubing spacing and loop length, and how the manifold position changes them in where to put the radiant floor manifold. Loop-length limits come from the tubing manufacturer, so ask which limits apply to the tubing quoted.
6. Who designs the loops, what the bid includes, and handover
- Who calculates the room loads and draws the loop layout, and who reviews them for your house and the selected system?
- Which drawings, assumptions, tubing specifications, loop lengths and design settings will be documented?
- Does the bid include floor preparation, insulation, tubing, manifold, controls, connection to the boiler or heat pump, and restoring the floor? What is excluded?
- Who coordinates the heating contractor, the concrete or thin-slab crew and the flooring installer, and how are changes priced and agreed?
- Who pressure-tests the tubing before it is covered, following the selected system's instructions, and records the result?
- Who handles startup, loop flow balancing, a controls check and the initial warm-up the floor construction needs?
- Will you receive the final layout, loop labels, test and startup records, operating instructions and warranty information?
Keep the answers with each bid so you can compare scope, not just totals. Agree on the checks before work starts: EN 1264-4 provides for a pressure test before the slab is poured over the tubing. Ask your contractor for the instructions that apply to the system you chose instead of copying settings from another product.
Next steps
- Already have a layout or a bid? Read the radiant floor heating design guide and check what it documents.
- Want to understand the tubing layout? Read about tubing spacing and loop length.
- Choosing a floor covering? See how water temperature and coverings change floor output.
- Renovating an older house? Read what to measure before retrofitting radiant floor heating.
Prepare your layout in HeatAlgo
Once you have the information, you can prepare a hydronic radiant floor layout for tubing in a slab or thin slab in HeatAlgo's radiant floor heating software. You enter the room loads, check the inputs and review the layout. You can then buy the printable plan and PDF report to discuss with your contractor, who should review the proposed design for your house and selected system before installation.
Start a free radiant floor layoutA HeatAlgo report follows EN 12831-1 and EN 1264, not ACCA Manual J, and is not accepted for permits or rebates.