In this guide, we will look at the two main types of water based underfloor heating systems available, a brief overview of how to fit an underfloor heating system, the different types of floor finish that can be used and how they are fit.
For those looking for more thorough and in depth instructions regarding the installation of our Rapid Response system, please use our Rapid Response fact sheet that can be found here
How To Fit Underfloor Heating
This guide will primarily focus on water based underfloor heating systems.
There are two main ways to fit water based underfloor heating systems – the traditional and most well known is an ‘screed’ system, the second and more modern way is known as an ‘overfloor’ or overlay system.
A short guide on screeds
Screed is typically a mix of cement and sand and is used to create a smooth, level surface for the final floor covering. It is typically poured on top of insulation (such as Cellotex & Kingspan) to create the internal floors of new build properties.
Traditional screeds made of sand and cement mixtures are usually 55-70mm thick and can take up to 80 days to dry fully.
Chemical Screeds have a different composition and can be much thinner. These screeds can be poured much thinner (35-50mm) depending on their make up and also dry more quickly (in some cases as little as 2 days).
Screed Underfloor Heating Systems
Screed Underfloor heating systems consist of underfloor heating pipe first being fixed to the insulation before the screed is poured, then buried in the screed. The floor finish is then laid on top of the screed.
This leads to long warm up and cool down times. Due to low controllability they’re well suited to large commercial areas; providing low level background heat.
When chemical screeds are used, the heat up times are much quicker than traditional screeds due to their chemical make up and thickness.
These systems are often used in new builds due to the fact that the screed will be poured anyway in order to provide the structural base for the floor finishes.
Overfloor & Overlay Underfloor Heating Systems
Unlike in screed systems where the heating pipes are buried in the screed structural base, Overfloor heating sits on top of the structural base and beneath the floor finish. These systems, such as our Rapid Response system, have much faster heat up times and gives the users all the benefit of a floor heating system as well as being far more controllable.
These systems are sometimes used in new builds and new build areas (extensions) as the users prefer the idea of a more controllable system.
The systems are perfect for home improvement and renovation projects, as it is not necessary to dig up floors and subfloors.
Key advantages of Water Based Overfloor systems, to bear in mind when considering your needs.
– They use low water temperatures (30-45 degrees)
– They can reduce energy use by 25% compared to radiators and 60% compared to electric UFH
– They maximise efficiency from all current heat sources
– They are the perfect partner for heat pumps and other future CO2 free heat sources
– Removing radiators gives the user 15% more liveable space, so they can design their rooms freely
– Unlike systems buried in screed, they are quick to warm up & easy to control – only using energy when needed.
– Quick to install, as no waiting for screed to dry and no joins in the floor.
Comparing Overfloor / Overlay heating systems
There are many ways that Overfloor systems are installed. Systems generally include pipe, pipe fixing, manifold(s) and controls.
Typically, Overfloor systems use high density panels to hold the pipe in place, spread the heat and provide a surface for the floor finish to be laid on. Some panels are made of insulative materials to insulate against downwards heat loss & to guide heat into the room, these should have a conductive layer on top (ie thick aluminium cover) such as our Rapid Response system. Other panels are made of conductive materials and spread heat, these will need an insulating layer beneath.
Another method fixes pipes in place with a castellated panel and covered with a thin renovation screed. However, often this adds time and money without bringing benefits, requiring a longer installation, adds significant weight to suspended floors, and do not protect against downwards heat loss without further insulation.
When comparing overfloor systems, consider supply cost, ease of installation and the best performance for you.
A brief summary of how to fit ‘Screed’ underfloor heating systems in a new build
Assemble and fix the manifold in place
An underfloor heating manifold acts as the key distribution point for your underfloor heating system. taking warm water directly from your heat source, mixing it down to the suitable temperature and distributing it around your underfloor heating pipes.
Fix underfloor heating pipes
Lay thick polyisocyanurate (PIR) insulation boards insulation boards such as Kingspan or Cellotex according to building regulations.
Depending on your Underfloor heating supplier, you will have been supplied with an Pipe Layout plan, showing where to position your manifold and how lay your pipe. Study the plan.
Fix perimeter strip around your room to provide an area of expansion. Depending on your supplier this will be supplied with your system.
Prepare and sweep the area, ensuring there are no nails or debris. Then fix your pipe to the insulation boards according to the pipe layout plan.
There are many different ways to fix the pipe to the insulation. Different types of fixings include; staples, clip track and castellated panels. None of these will make a difference to the performance of the system, but some are easier than others to install and keep uniform distances between pipe loops. It’s important that the pipe is fixed in place before the screed is laid.
Connect to the manifold
Once the pipe has been laid according to layout plan, connect the pipe work to your manifold according to your suppliers instructions. If you are using a Wunda system, instructions and videos can be found on our site and with your delivery. Generally, this is a straightforward job.
Pressure test
Once the pipe has been connected to the manifold, it’s time to fill your system with water and pressure test according to the instructions supplied by your supplier. Wunda Users will be supplied with the instructions and necessary equipment to pressure test.
It is very important to pressure test the system before the screed is poured to make sure there has been no damage to the pipe work that might cause leaks.
Pour Screed
Now that your underfloor heating pipe work and manifold has been installed and pressure tested, it is time to pour the screed.
Fit floor finish
Once the screed has dried, it is possible to lay your floor finish of choice. More information on floor finishes can be found later in the article and also here – Learn more about floor finishes and underfloor heating here
A brief summary of how to fit ‘Overlay / Overfloor’ systems in new builds and existing homes
PLEASE READ:
It is important to consider your choice of supplier and type of panel with the installation in mind. Some suppliers are essentially resellers and simply not set up to provide quick and easy support to their customers. Please also consider the type of panel. Some panels are heavy to handle, hard to cut and require expensive adhesive with long drying times. These factors can literally add many days to your install time and thousands of pounds to your supply costs, without any performance benefits.
A Wunda Rapid Response system is lightweight, easy to handle and cut and uses a quick drying adhesive. A whole ground floor can be installed across a weekend ready for your floor finish. Unlike many other companies, we have a well-staffed team of experts on hand to help and support you every step of the way.
The guide now will show you a typical install of a ‘Wunda Rapid Response Overfloor’ type system.
Prepare the area
Ensure your subfloor is clean, flat, dry, level, stable, and structurally sound. Remove any skirting boards & doors if you are installing in multiple rooms or the entire floor.
Depending on your Underfloor heating supplier, you will have been supplied with an Pipe Layout plan, showing where to position your manifold and how lay your pipe. Study the plan.
Assemble and fix the manifold in place
An underfloor heating manifold acts as the key distribution point for your underfloor heating system. taking warm water directly from your heat source, mixing it down to the suitable temperature and distributing it around your underfloor heating pipes. Fix the manifold in place according to your layout plan.
Fit your panels
Depending on your floor finish, you may need to install perimeter strip around the perimeter of the room(s) to allow for an expansion gap. Depending on your supplier, this will be advised and supplied with your system.
Dry lay boards onto the floor making any cuts where required using the fine tooth saw/craft knife, use the straight edge rule to assist in making straight cuts.
- Take care when cutting the boards wearing work gloves as the aluminium can be sharp.
- Keep any offcuts as these may be useful in other areas.
Use WundaSpray adhesive, or the adhesive supplied by your supplier, to bond the boards to the sub floor. Make sure boards are in the appropriate locations when dry laying as they cannot be moved once bonded without damaging the boards. The boards need to be secured next to each other with no gaps between them.
With boards firmly secured, use router set at the appropriate height (16/12mm) to route any additional channels required as marked. Hoover any debris made whilst doing this step.
Lay your pipe
Following the pipe layout and starting at the manifold lay the pipe securely into the channels the boards.
Connect to the manifold
Once the pipe has been laid according to layout plan, connect the pipe work to your manifold according to your suppliers instructions. If you are using a Wunda system, instructions and videos can be found on our site and with your delivery. Generally, this is a straightforward job.
Pressure test
Once the pipe has been connected to the manifold, it’s time to fill your system with water and pressure test according to the instructions supplied by your supplier. Wunda Users will be supplied with the instructions and necessary equipment to pressure test.
Lay your floor finish.
Some more information on floor finishes can be found later in the next section of this article and also here – Learn more about floor finishes and underfloor heating here
For those looking for more thorough and in depth instructions regarding the installation of our Rapid Response system, please use our Rapid Response fact sheet that can be found here
The Different Types Of Flooring
Many people believe that solely tiles can be their flooring of choice with an underfloor heating system. While tiles are a good choice and work well with underfloor heating systems as they are convectors, most flooring types can actually be used.
Though tiles are ideal in certain rooms, they are not most people’s choice for the flooring of an entire home, and you can use carpet, laminate, LVT, and wooden flooring.
Each type of flooring has its own characteristics which have to be considered when fitting the underfloor heating system.
Once you have decided which type of flooring you want, the task of getting the heated floor up and running can be straightforward.
When you do begin to think about what type of flooring you want, it is vital to follow the guidelines for that specific type of flooring. For instance, some types of flooring can simply be easier to install than others.
The article will now consider how to fit the floor finishes.
For more information on how different floor finishes work with underfloor heating please follow this link – Learn more about floor finishes and underfloor heating here
The Considerations For Fitting Flooring
The next section will cover some considerations for the most commonly DIY friendly types of floor finish: LVT, Laminate and Wood.
Check for any unevenness in the subfloor and use a floor levelling compound if necessary. This is to ensure that the floor heats evenly as any gaps could allow the heat to escape. The subfloor should also be clean and damp-proof.
How To Fit LVT Flooring
Make sure you take the time to acclimatise your LVT flooring by leaving the boxes of flooring in the intended room at the room’s normal temperature for 48 hours before fitting.
Use an LVT underlay for the right support, and you could use a self-adhesive LVT underlay that has anti-slip properties. Ensure an even gap between the wall and the LVT board with 7 to 10 mm spacers.
The actual installation of LVT flooring should be straightforward with click vinyl tiles. In accordance with Karndean and Amtico, Wunda advises that LVT flooring is laid onto a screed or renovation screed to provide a stable base to work on. More information can be found here on how to fit LVT and vinyl flooring
How To Fit Wooden Flooring
As with LVT flooring, it is advised that you acclimatise wooden flooring to its surroundings to maintain the moisture levels. This should be for at least a week under normal living conditions.
You will need room for expansion with solid wood flooring and a gap of around 10 to 12 mm would be required on the perimeter of the installation. This gap will be covered by skirting boards.
When installing the solid wood flooring, check each floorboard, and you can use randomly placed joints for less waste and an impressive look.
More information can be found here on how to wood flooring
How To Fit Laminate Flooring
Laminate flooring either uses a tongue and groove or a click-fitting system and the underlay can differ too.
Start in the corner of your longest wall and lay the laminate flooring with the tongue edge lying against the wall.
Next, place 10 to 12 mm spacers to create an expansion gap between the board and the wall with two spacers along the length and one across the width of the board.
Now the fixing can begin though ensure that the alignment of the flooring is exact, and you will be required to cut the final board to fit the remaining gap.
More information can be found here on how to laminate flooring
Final Thoughts
The type of flooring you decide on should work for your home for the aesthetic look you desire and have the heating properties you want.
This may differ depending on the room as you may need water-resistant flooring such as LVT or tiles in the bathroom and kitchen with more versatile flooring in other places.
It should be a simple task to fit the underfloor heating once you consult an expert like Wunda and follow the provided layouts and instructions.
Contact us if you have any questions before fitting your underfloor heating system.
/journal/2022/05/11/how-to-fit-underfloor-heating/
If you have any questions – please get in touch
Or if there’s anyone you know who might benefit, please feel free to share!
We’re always happy to help,
View Our Case Studies