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Screeded Floor

Screeded Floor

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  • Screed can be either traditional 4:1 sand cement with additive (75mm depth recommended) or freeflowing liquid screed (55mm depth recommended). 
  • All insulation joints must be thoroughly taped when using freeflowing screed. 
  • Floor insulation has the dual purpose of preventing the downward loss of heat and securing the pipe clips. 
  • Insulation boards should be close butted with staggered joints. 
  • The thickness of the floor insulation will be determined by building regulations and responsibility for meeting these rests with others. When using EPS Tackerboard a rule of thumb is for 75mm thick insulation on Ground Floors and for floors above unheated areas such as car parks; and 25mm on upper floors. 
  • The density of the insulation will be determined by the type of building e.g. a warehouse that will have heavily laden fork lift trucks running over the floor will require a dense insulation to reduce the risk of the screed cracking. 
  • Screeded floors must be allowed to dry and reach their maximum strength - 28 days - before heavy plant such as cherry pickers and scissor lifts are driven over them.
  • Assuming the appropriate insulation has been used, and the screed has dried, the best way to avoid cracking of screed when using heavy plant is to lay 2 x 12mm ply boards at opposite angles on top of each other.
  • Fast drying screeds such as Ardex, Flexidry, K-screed and Truscreed use super-plasticisers to reduce the amount of water, which in turn accelerates drying.
  • Edge insulation will be required around the floor perimeter to allow for the expansion and contraction of the screed and to prevent the loss of heat through the wall. 
  • Heat output from a screeded floor is 100W/sm at a room temperature of 20 deg C and a floor temperature of 29 deg C. When screeding is in progress, the pressure gauge on the manifold should be regularly checked. There are different types of floor insulation – expanded polystyrene (EPS), polyisocyanurate, polyurethane, XPS and mineral wool.



  • Can be used for residential and commercial projects.
  • Has a BRE rating of A+.
  • The polystyrene is covered with a woven cover with a 50mm grid pattern that allows for straight pipe runs and protects the insulation from the screed.
  • Completely waterproof - even if completely immersed in water, once dried out, no harm is done to the insulation.
  • Comes in different densities - EPS 70; EPS 100; EPS 150 and EPS 200.
  • EPS 100 gives excellent grip to clips, so when screed is in progress, it is more difficult for the snaking screed pipe to knock the clips and underfloor heating pipe out of place.
  • EPS is 98% air and 2% cellular matrix - it is consequently light and Health & Safety friendly.
  • High compressive and compression strengths - strength tests over 25 years confirm this.
  • Thermal qualities are preserved over the lifetime of the insulation.
  • A more economic option compared to other types of floor insulation.
  • EPS does not contain HCFC's or CFC's.
  • EPS has no nutritional value and does not provide food for rodents or insects.
  • Can be used with all screeds and cement, lime, Gypsum and anhydrite screeds.
  • Tested and manufactured in accordance with BS 13163.
  • Carries the CE Mark.
  • Manufacturer operates ISO 9001 - 2008 quality system.
  • Bespoke thicknesses can be supplied between 20mm and 200mm.
  • 50mm overhang on two sides of each board allowing easier taping of joints.
  • Manufactured using a steam process which allows the process to use re-useable energy.
  • All EPS waste can be recycled back into production.
  • EPS has zero depletion potential and zero global warming potential.
  • EPS reduces CO2 emissions up to 50%.


EPS 70

EPS 100

EPS 150

EPS 200

Thermal Conductivity





Compression @ 1% kPa





Compression @ 10% kPa







  • Good thermal conductivity - Kingspan K3 - 15mm - 24mm = 0.024W/mk; 25mm - 44mm = 0.023W/mk; 45mm + = 0.021W/mk.
  • CFC and HCFC free.
  • ISO 9001 quality systems in place.
  • Kingspan K3 is a phenolic insulation with a compressive strength @ 10% compression of 150 kPa.
  • Resistant to mould and does not provide food for vermin.
  • Has a BRE rating of A+.
  • Kingspan recommends 500 gauge polythene sheet to be laid over the K3 insulation before the pipe is installed and Screed laid.
  • Kingspan states that boards that have been allowed to get wet should not be used.
  • Details about the above products are available on the respective websites.

Site conditions for the storage of insulation vary considerably.



  • Edge insulation is used to insulate the perimeter of each room.
  • It must be installed for the full depth of the screed to avoid cold bridging.
  • In addition to preventing heat loss through the wall it allows expansion and contraction of the screed and helps to prevent cracking.
  • We recommend the use of a specially designed perimeter strip - cutting thin strips of insulation board creates on site health and safety risks.
  • The strip we use is made from closed-cell expanded polyethylene.
  • It has an adhesive strip for fixing to the wall.
  • It has a polyethylene skirt on the panel side, which prevents screed from getting down between the edge insulation and the floor insulation - especially desirable where liquid screeds are being used.
  • The edge insulation we use is 7mm thick and 150mm deep.
  • Edge insulation can also be used to diffuse heat where there are a large number of underfloor heating pipes close together e.g. in a narrow corridor.



The most economic floor insulation option is for plain EPS insulation covered with polythene sheets.

In order to get a neat installation it is essential that, after laying the insulation floor panels and polythene, it is essential that the floor is measured and marked out.

The neat installations in the above photographs were achieved by marking out and following chalk ‘ping' lines on the polythene.

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UHMA - The trade association for surface heating and cooling.


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