What to Look for in a Trade Underfloor Heating Supplier in 2026

Choosing a trade underfloor heating supplier in 2026 sits right on the fault line between design intent and site reality. A drawing can look perfect, a product spec sheet can tick every box, yet the project still falls over if the system arrives late, the manifold is short of ports, or the design assumptions do not match the floor build up that actually gets installed.

The direction of travel in UK heating design keeps turning toward lower water temperatures and tighter performance expectations. Part L guidance in England has been widely interpreted across the market as pushing new or fully replaced wet systems toward a maximum 55°C flow temperature where feasible, and heat pumps are commonly designed to run lower than that, often in the 30°C to 45°C range for underfloor heating according to CIBSE learning material. That shift changes the questions a supplier needs to answer for you, because low temperature heat demands better emitter design, careful pipe spacing decisions, and correct circuit sizing.

A trade focused supplier earns their keep by reducing decisions you have to guess on site, while giving you enough technical confidence to stand in front of a client, a clerk of works, or a main contractor and say, "Yes, this will perform." The supplier that gets chosen for the next few years becomes part of your reputation, which is why it is worth being picky.

Why a trade focused supplier matters more in 2026

A homeowner buying a small electric mat kit can accept a few unknowns. A contractor delivering five plots with mixed floor zones, stairwells, open plan glazing, and a heat pump interface cannot.

A trade focused underfloor heating supplier should be set up for the way projects really run.

• Design risk is higher at low temperatures. A system can fail quietly, rooms drift a couple of degrees cold, call backs start, and you spend weeks proving whether it is controls, balancing, fabric performance, or emitter output.
• Specification chains are longer. You might be answering to an M and E consultant, a developer, building control, or an energy assessor. Each one can ask for the same information in a different format.
• Procurement is tighter. Projects are scheduled around first fix and screed dates, and a missed delivery does not only delay the heating.

A supplier that understands trade workflows tends to offer structured design packs, clear performance assumptions, and technical support that speaks your language. A supplier that is not trade oriented often treats every enquiry like a retail basket, and that is where friction starts.

Essential supplier services that reduce risk on real sites

A serious supplier should provide more than boxes on a pallet. The services below are the ones that consistently prevent problems from reaching install day.

CAD and layout support that matches the floor plan you will actually build

Ask what they need from you to produce a usable pipe layout. A good answer includes floor plans with dimensions, room uses, glazing positions, and the proposed manifold location, plus the floor build up and insulation specification.

The deliverable you want is a layout that helps installers, not a pretty picture. Look for:

• Pipe routes that respect door thresholds, kitchen islands, and sanitary zones
• Clear loop identification that corresponds to manifold ports
• Loop lengths shown for each circuit so balancing is practical
• Notes on perimeter spacing and any areas to avoid fixing into

If the supplier cannot tell you how they handle revisions when the plan changes, the service is not really designed for construction projects.

Flow and return temperature assumptions written down

Underfloor heating performance depends on the relationship between flow temperature, floor surface temperature limits, and the room heat loss. A supplier should be comfortable stating their assumptions clearly.

Questions worth asking include:

• What design flow and return temperatures are you using for this project, and why
• What room design temperature are you targeting
• What floor surface temperature limits are assumed for occupied spaces
• How do you handle mixed heat sources, such as a heat pump for space heating and another heat source for hot water

Written assumptions protect everyone. They also make it easier to explain to a client why pipe spacing or floor finishes matter.

Heat loss inputs and sanity checks

Many suppliers will base output on your heat loss figures. That is fine, but only if they sanity check them. A good supplier will query anything that looks off, for example a bathroom with very high watts per square metre, or a large open plan space with a surprisingly low load.

This is not about arguing with the consultant. It is about catching errors early, because an error that slips into the design often shows up later as a cold room, a noisy pump, or a manifold that never balances.

System compatibility: pipe spacing, manifold sizing, and floor build up

The heart of supplier evaluation is whether they help you align three things that must match, the required heat output, the floor construction, and the hydraulic limits of the circuits.

Pipe spacing decisions that are explained, not guessed

Pipe spacing drives output, response time, and comfort, and it also drives how much pipe is needed and how many loops you will be commissioning. Typical UK practice often sits around 100 mm, 150 mm, or 200 mm centres depending on load and floor construction, with tighter spacing used where higher output or lower flow temperatures are required.

A supplier should be able to justify spacing choices in plain language, linked to your design temperatures and the floor build up. If you hear only blanket rules, that is a warning sign.

Practical checks you can request:

• Pipe metres per square metre for the chosen spacing so you can sanity check quantities
• A note on perimeter zones where extra output may be required
• Any special treatment for areas with large glazing or external doors

Loop lengths and pressure drop limits

Long loops increase pressure drop and can create uneven temperatures across the circuit. Across UK trade guidance, a common rule of thumb is to keep 16 mm pipe circuits around 100 m maximum, allowing for the run from the manifold and back, and to split zones into multiple loops where needed.

A capable supplier will:

• Show each circuit length and highlight any circuit pushing the limit
• Recommend pipe diameter choices where relevant
• Specify the design flow rates per loop so commissioning is not guesswork

Manifold sizing that supports commissioning and future service

Manifold sizing is not only about counting loops. It also affects serviceability, actuator selection, and how clean the install looks.

Ask for clarity on:

• Port count and spare capacity, if any
• Flow meters and isolation valves included in the specification
• Whether mixing sets are required for the heat source and design temperatures
• The recommended location for access, including allowance for pipe bend radii and future servicing

A supplier that supplies a manifold but avoids discussing access, balancing, and actuators is leaving you exposed.

Floor build up compatibility that respects site constraints

Floor construction can make or break the outcome. Screeded systems, low profile retrofit panels, suspended timber solutions, and overlay boards each have different response times and practical constraints.

The supplier should ask you about:

• Insulation type and thickness, including edge insulation and breaks at thresholds
• Screed type and thickness, and whether it is sand and cement or anhydrite
• Finished floor coverings and their thermal resistance
• Structural limits and any height restrictions at doorways and stairs

If those questions do not come up, you are likely being sold a generic kit rather than a project specific solution.

Stock, responsiveness, and delivery lead times: how to check what is real

Every supplier promises fast delivery. The ones worth keeping are the ones who tell you what is in stock, what is made to order, and what happens when a courier misses a scan.

Responsiveness that protects your programme

Responsiveness shows up in the awkward moments, when a screed date moves, a plot swaps from screed to suspended floor, or a client asks for zoning changes late on.

Ways to test this before you commit:

• Send a technical question that requires a real answer, not a brochure excerpt
• Ask how design revisions are handled, and what the typical turnaround is
• Ask who supports you during commissioning if readings do not match the design

A supplier who responds quickly with clear, practical guidance often saves hours of site time.

Stock transparency

A supplier should be able to confirm what is held in the UK, what is dispatched next working day, and what has longer lead times.

Look for straightforward information on:

• Pipe coil sizes and availability by diameter
• Manifold port counts and whether specific sizes are stocked
• Controls and actuators availability, because these can become the hidden delay
• Consumables and fixings, because missing small items can stop a whole plot

Delivery lead times that are aligned to trade expectations

UK mechanical supply logistics has continued to tighten, with trade customers increasingly expecting predictable next working day delivery for stocked items, supported by tracking and scheduled drops on site. The detail that matters is the cut off time, the delivery days for your postcode, and how the supplier handles redelivery when access fails.

Ask for:

• Cut off time for next working day dispatch
• Confirmation of carrier and tracking process
• Options for timed delivery, site contact requirements, and pallet drop constraints

Protecting your reputation on complex and large scale projects

Large jobs amplify small errors. A missing actuator is annoying on a single plot. On a multi plot site it becomes a weekly disruption.

A supplier that helps you protect your reputation usually brings three qualities.

Clear documentation you can pass down the chain

Good documentation reduces arguments and speeds up approvals. This can include:

• Layout drawings with loop labels and pipe spacing
• Manifold schedules with loop lengths and design flow rates
• Commissioning notes and balancing targets
• Temperature assumptions for the heat source interface

Commissioning support that respects how site teams work

Underfloor heating systems often look finished long before they are set up correctly. Commissioning support should cover flushing, filling, pressure testing, balancing, actuator checks, and basic control strategy.

A supplier who can talk your engineer through expected flow rates and temperature differentials is helping you deliver comfort, not just completing an install.

Consistency across plots and phases

Multi plot sites benefit from repeatable specifications. Your supplier should be able to keep designs consistent, flag plot variations clearly, and supply kit packs that match each unit.

If the supplier can provide labelled packs by plot, with the drawing version included, site errors drop fast.

A practical evaluation checklist you can use before opening an account

Use these questions in a phone call or email and listen to how the answers are delivered.

• Do you offer project specific design packs, and what is included
• What design flow and return temperatures do you typically work to for heat pump and boiler projects
• How do you determine pipe spacing, and will you explain the reasoning in the design pack
• What loop length limits do you work to for 16 mm pipe, and how do you handle a zone that needs more than one loop
• How do you size manifolds, and do you include details on actuators, balancing, and access
• What information do you need from me about floor build up and finishes
• What is actually stocked for next working day dispatch, and what is the cut off
• Who provides technical support when the system is being filled, balanced, and commissioned

If you want a supplier that feels like a partner, ask them how they handle problems. The answer tells you more than any marketing claim.

Where ThermRite fits into a trade procurement approach

ThermRite positions itself as a trade focused supplier, and their published guidance leans into low temperature system design and compliance themes that matter in 2026. When evaluating them, apply the same checks you would use for any supplier, confirm design pack contents, written temperature assumptions, loop length methodology, and dispatch reliability for the products you use most often.

Summary and next step

A strong underfloor heating supplier in 2026 gives you three things, a design that stands up at low temperatures, a kit that matches the floor build up and hydraulic limits, and support that stays available when the programme gets messy.

If you are reviewing suppliers for upcoming plots or commercial zones, take one live project and run the evaluation checklist as a structured comparison. Once you find a supplier that answers clearly, documents assumptions, and delivers consistently, open a trade account and standardise your approach across projects so every install is easier to manage and easier to defend.

Frequently Asked Questions

What information should a supplier ask for before producing an underfloor heating design?

They should ask for dimensioned floor plans, room uses, glazing positions, target room temperatures, heat loss figures if available, proposed manifold locations, heat source details, and the full floor build up including insulation and final floor finishes.

What is a sensible maximum circuit length for common underfloor heating pipe sizes?

Many UK trade designs keep 15 mm to 16 mm pipe circuits around 100 m maximum, including the run to and from the manifold, because longer circuits can create excessive pressure drop and uneven floor temperatures. The exact limit depends on design flow rate, pipe diameter, and pump capability.

How can a contractor verify a supplier can really support next working day delivery?

Ask for the dispatch cut off time, confirm which items are stocked in the UK, request a written lead time for manifolds, controls, and actuators, and check how tracking and failed delivery attempts are handled for your postcode and site access arrangements.