What is a floating floor and how do you insulate it?

Insulating a floating floor

There’s a lot of jargon in this industry, but quite often it’s all very simple. Take ‘floating floors’ and how you insulate them.

So, what is a floating floor? A floating floor is typically taken to mean a lightweight construction where chipboard, gypsum or cement fibre board floor panels are ‘floated’ across the top of the rigid insulation layer. Floating floors are used most often in domestic buildings especially when retrofitting or refurbishing an existing building. This is because they are quick, lightweight and easy to install, thinner than screed options, with no wet trades and no drying-out time. They also allow for fast heating response times.

How to insulate a floating floor?

The layers would be, from top down:

Floor finish (eg carpet/ laminate floor, timber boarding. As floating floors are by their nature flexible, care should be taken when specifying tile finishes which are more suited to less flexible substrates)
Tongue and Groove flooring (typically 18mm T&G chipboard or cement  / gypsum fibre boards)
Separation layer (500 gauge polythene)
Insulation laid continuously (eg Kingspan Thermafloor TF70)
Damp proof membrane if required
Screed (if existing)
Concrete slab

What about for heavier items? For items such as bath footings or the base of toilets then a timber batten would be used. Similarly, where there is heavier point loadings such as in door thresholds or at the bottom of stairs, then again you would use a timber batten.
For more information have a look at Kingspan Thermafloor TF70

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Kingspan Insulation is a market leading manufacturer of optimum, premium and high performance rigid insulation products and insulated systems for building fabric and building services applications.

0 comments on “What is a floating floor and how do you insulate it?
  1. Hi I am currently converting my garage into a kitchen. Can i lay 50mm TF70 then 18mm tongue and grove chipboard or would it be better using 50mm batons at 600mm centres then 18mm plywood. The finish would be electric underfloor heating then tiled.

  2. Hi Karl, thanks for your question. For a kitchen where there will be heavy equipment such as cookers and floor standing units, we would recommend using battens and then filling between with insulation.

  3. Hi

    I live on ground solid floor flat I want to use dpm, king span 5″ then lay 2×2 or 3×2 on top fixed together at the perimeter and using noggings, then engineered boards secret nailed, would this be ok ??



    • Dominic,
      Thanks for taking the time to get in touch. If we understand you correctly, you are asking whether it is ok to place the timbers on top of the insulation directly. We would be concerned that this would mean that there could be significant point loading on the insulation which could compress that insulation. So, we wouldn’t recommend that approach. You would be fine to lay the engineered boards as a true floating floor unless the manufacturer has specifically stated you shouldn’t.
      Call us and one of our advisors can talk to you directly on 01544 387 382.

  4. Hi, I’m building a new garden building re-using a substantial concrete slab from a previous building. (350mm thick). I am planning to lay a DPM, then 100mm kinspan boards, then a vapour barrier then a 12mm laminate floor. Do I have to use the 18mm chipboad as well? Use will be as a games room / home office so no heavy equipment in there.
    Secondly do I have to use Thermafloor or will other Kingspan boards work as well for such a ligfhly loaded building?
    Thanks for your help.

    • Hi Andy,

      Thanks for your questions. When using Thermafloor TF70 within a timber floating floor system we would recommend the use of 18mm tongue and groove chipboard to allow for the spread of any potential loadings. If not from heavy equipment it would help the spread of foot traffic and further protect the insulation from any impact damage. Thermafloor TF70 is the most appropriate product for floating floors within domestic projects as its compressive strength would generally exceed the required loadings.

      Let us know how you get on.

  5. Ive got a concrete floor in my kitchen that had 22mm batons and 18mm chipboard.Some batons were screwed some were not.The concrete looks dry .If I screw all the batons down before putting on 18mm ply will this cause damp and if so how do I prevent it.I want to screw the batons because im tiling on top.
    Thanks Brian

    • Hi Brian,

      As long as your fixings for the battens do not penetrate the damp proof membrane underneath your concrete you should be fine. So, you will need to know the depth of concrete you have. Your existing screws will give you an idea of what has worked previously.

  6. Iam looking to convert my garage into a bedroom. And have been told I need to insulate the floor. At present the floor is concrete . I have two options to remove concrete and insulated or build a floating floor. What are the regulations for measurements and how much insulation what will I need to do this option. ?


  7. Hi I am converting an office/study into a living area for my mother,the floor was carpeted directly onto the concrete floor with no visible signs of damp penetration.
    I was going to put down 50mm insulation and 18mm chipboard,do you think it will need a vapour barrier under the flooring?

    • Hi Angus,

      Yes, we would recommend using a damp proof membrane if there isn’t one in the concrete floor. The installation process is as follows (taken from our Thermafloor TF70 literature):
      • The surface of the concrete slab should be smooth, flat and free from projections. In accordance with BRE Good Building Guide 28 Part 1 (Domestic floors: construction insulation and damp –proofing), irregularities should not exceed 5 mm when measured with a 3 metre straight edge.
      • A thin layer of cement / sand mortar, a levelling screed, or a proprietary levelling compound can be used to achieve a level surface, and prevent the boards of Kingspan Thermafloor® TF70 from slipping under the timber floor boards, if required. This should be allowed to set, harden and dry (approximately 1 day per mm) before proceeding further.
      • If there is no damp proof membrane in the concrete floor, one (minimum 300 micron / 1200 gauge polythene) should be laid with joints well lapped and folded, to prevent the passage of ground water, over the concrete floor slab, prior to installing the insulation boards.
      Hope this helps.


  8. Hi,

    Just a quick question with reference to some information in your literature, may be obvious but here goes.

    Can you advise why only a single layer of insulation is recommended using this method?

    I assume this is because the insulation layers are not fixed, but can you please advise.

  9. Hi there, thanks for the blog post, I was under the impression screeding can be done over insulation boards? so from top down

    Final finish
    Insulation boards (eg thermafloor)

    Is this not the case?

  10. Is a floating floor membrane enough to prevent boards rising when laid straight on to a floating floor or should there also be a layer of insulating board?

    • Hello.

      Not sure I understand your question completely. First and foremost your concrete floor should be dry and damp-free. You can then lay the insulation directly on top of that concrete slab. The membrane (vapour control layer) then sits on top of the insulation board. Finally your tongue-and-grooved chipboard would be laid on top of that. The membrane itself is only there as a vapour control layer.

      Hope this helps. Let us know if we’ve got the wrong end of the stick!

  11. Hi
    I’m fitting out a new ground floor, rooms 6m x 3.4m and 6 by 2.4 with c150mm to work with from beam and block floor to FFL with wet underfloor and 18mm engineered wood finish on to go top. I can’t decide between 65mm of screed over 70mm of TF70 or just to float the floor over 130mm of TF70 with aluminium heat plates direct into the insulation.

    My worry is about stability of a floated floor that big direct on insulation – would I need additional joists – I know they are needed for doorways etc?

    Many thanks.

    • Hi Phil,

      This sounds like you are using the insulation to make up levels rather than to achieve any specific U-value as you have chosen two very different insulation thicknesses.
      To answer your question though, the floor will be stable with that amount of insulation. A single layer of insulation is advisable. The floor edges and skirtings as well as the weight of the engineered wood finish will keep the floor stable too. You can add extra joists for door thresholds and it is advisable if the floor is being used for heavy fixtures and fittings or heavily trafficked areas (eg shop floors).
      If you’re unsure or want to talk it though do give us a call on 01544 387 382.

  12. Hi, I’m fitting a new kitchen to an old victorian house, 1902. The floor base is concrete and so I’m assuming there is no damp proof. I have an inward opening door with a clearence of 33mm. I intended to lay a membraine of 1200g/300 then 20mm of TF 70. I then need to use a vapour barrier before floating floor. My two questions are, can I use the same 1200g/300 for the vapour barrier and, because of the limited clearance, can I use a 9mm ply board on top as my floating floor?

    Thanks in anticipation of your help.

    • Hi Phil,
      18mm of plywood is the minimum thickness of timber that is required. 9mm of timber will not be substantial enough. Also as this is a kitchen some timber battens or supports may be advisable around heavy fittings such as the cooker.
      You asked about the vapour barrier – it is ok to use the same gauge as you have described.
      So, you may still be very tight for space. A couple of options would be to dig down and lay a new concrete floor. Another and simpler option would be to shave off the bottom of the door. This may of course lead to a step of sorts, but it would allow you the space to accommodate the insulation.

  13. Hello,

    I have a concrete floor in my cellar/ground floor (ground level at the front, and underground at the rear of house. The floor has a waterproof membrane and is dry. However the room suffers from atmospheric damp and furniture/carpet on the floor goes moldy.

    In your opinion, should i get a wooden floating floor fitted above it (ie a floor on battons with air gap under it) to help? Or is it better to fill gap with polystyrene sheets to stop cold air hitting it?

    Thanks very much for your advice

    • Hello Yvonne,
      The first thing you need to do is to get to the root cause of the damp problem. The moisture has to be coming from somewhere (eg a shower or kitchen nearby, or potentially through the walls in the underground part of your room). The reason is that if you are adding a timber floor, then this is likely to suffer because of the damp. Dehumidifiers can help in this situation. Once the damp is controlled, and assuming you are heating the room, then a simple floating floor will be fine (use Kingspan Thermafloor TF70). Adding an air gap will do nothing in this situation, so it is ok to lay onto the floor with 18mm chipboard over the top.
      Hope this helps.

  14. Hi.
    im decided whether to do a floating floor or make a timber frame (when raising my garage floor). How much weight will the TF70 hold? i plan to have an exercise bike (55kg) and me (85kg) on it. Obv i wont be there all the time, but the bike will. Will a FFloor with 18mm chipboard (and laminate etc on top) be ok, or shall i build a timber frame?

    • Hi Andy,
      Where you have heavy exercise equipment or where the point loadings are potentially going to be high, then we would recommend putting the insulation between battens. 18mm chipboard will be fine by the way.

  15. Hi – I have just converted my existing conservatory to a room, and am knocking through to the lounge to make one larger room. Currently I have ceramic tiles fixed firmly to the floor of the conservatory on a cement base and a floating floor Beams/Floorboards in the lounge. The level difference is 30mm between the lounge floorboards and the conservatory tiles which are level. Can I use 30mm Kingspan Thermofloor TF70 directly on top of the tiles, then the normal laminate insulation followed by 18mm+ Laminate floor across both areas?



    • Hi Kevin,
      Thank you for your question. Yes, you can lay the 30mm of Kingspan Thermafloor TF70 on top of the tiles. This is assuming, of course, that the tiled floor is completely flat (which you say it has) and has a DPC in the construction. You will also need to follow the instructions in the product brochure including the separation layer above the TF70.

      Thanks again for your question and I hope this helps.

      Peter and Dee

  16. Hi there,

    I believe this question has been asked in a manor a few times but I am just trying to get a better understanding. . .

    I have an uninsulated 100mm concrete pad and require either a 50mm insulation level for a floating floor or a 70mm with battens. I would obviously like to go down the floating floor route for ease of construction and it saves me valuable room height, but it is in a kitchen area with heavy items. Why will the insulation accommodate heavy weights when a concrete screed is in place, with tonnes of material weight, and not when a sufficiently thick engineered wood is on top? If I was to use to overlapping layers of 18mm ply, would this not be capable of supporting a similar weight as 50mm of screed on top of the insulation??

    Many thanks for your time.


    • Hi Simon,

      This is a good question. A screed acts as a structural layer whereas the 18mm plywood is simply there to provide a substrate for the floor finish. Your point about using multiple layers of plywood is a good one, however this is untested and we can really only advise you on tried and tested constructions; in this case the use of a 65mm sand/cement screed or a specialist reinforced screed.


  17. Hi

    I’m converting a car port under my house in to a small office. I’d prefer not to baton the floor and lay ply or chipboard if at all possible. Is the following ok?

    Laminate floor (22mm)
    Separation layer (500 gauge polythene)
    Insulation laid continuously (eg Kingspan Thermafloor 75mm)
    Damp proof membrane
    Concrete slab

    Also, how would the above layers look if I wanted underfloor heating?


  18. Hi I am converting an outbuilding into a shower room . The existing floor is a concrete one which is about 100mm lower than the finished floor in the house. My thoughts were to spread a sand blinding, then a dpm ,then kingspan, then 18mm chipboard . My question is would the kingspan insulation be ok to support washing machine / fridge and for the shower and toilet. Or am I better off using a timber floor with kingspan inbetween.
    Many thanks in advance Mike

    • Hi Mike,

      Thanks for your question. If you want a build-up as indicated, we advise that on top of the concrete you lay the following items in the said order:

      – Damp Proof Membrane
      Kingspan Thermafloor TF70
      – Polythene layer
      – Chipboard

      However given that your floor will be supporting heavy loads, and to answer your question, yes we would advise that you lay the TF70 between timber joists so that these joists support the weight.

  19. I am trying to find out how much Kingspan is in a concrete slab floor. How much does a 50mm sheet compress down to? if at all?

  20. For a floating floor is it acceptable to use 600 x 2400 18mm structural 4 T&G OSB3 boards instead of the T&G chipboard.

  21. Hi

    I have a floating floor at the moment 50mm polystyrene and 20mm chipboard these are sitting on top of a cement base, im wanting to remove the old stuff replace with kingspan 40mm and 20mm hard underfloor heating overfloor panels eps300, ive been told the worl great on existing cement and floor boards, my question is would it work using 40mm underneath to raise the floor and insulate ?

    • Hi Adam,

      We recommend 40mm of Thermaroof TF70 for the floating timber floor, the build up and some basic underfloor heating advice is shown in the product literature, which can be downloaded here. However, we advise that you obtain specific underfloor heating guidance from the manufacturer of the system you are planning to use. This is because some systems require timber battens so that space can be created to run pipes above the insulation, or the pipes may run through expanded polystyrene.

      Hope this helps.

  22. Hi we have built an extension and need to do the floor….base all laid as per building regs, ie hardcore, sand, 100mm king span membrane 6inches of concrete but the builder didn’t finish off the job so now we have a floor 4inches lower as he under ordered the concrete.. We have been looking around and my husband been told to do a floating floor which we would like to do… We have already as I said a membrane, what I want to know is ! can he lay the 100mm then lay 18mm chipboard tongue and groove on top. Without laying even more membrane…..

    • Hi Chris

      Thanks for your question. Take a look at our Thermafloor TF70 product literature, which gives a suggested floating floor build-up on page 5 and guidance on how to install insulation below a floating floor on pages 9 / 10.

      You will see that the typical build-up shows (from the floor, up) concrete, damp proof membrane, insulation, polythene separation layer and then 18mm of T&G chipboard. Hopefully this will help in determining your own build-up.

  23. I’m currently working on a 1930’s property which has a basic suspended timber ground floor with a void under it.

    Instead of taking up all the floorboards and insulating between the joists, we were looking for a product that could be put directly on top of the existing floorboards that was perhaps 3 – 10mm thick, hard/sturdy enough with reasonably good thermal insulating properties that could then either have normal carpet underlay and carpet put directly on top for use in all ground floor rooms and perhaps the same or different product for the kitchen where tiled flooring would be used.

    Please could you advise if you have any products in your range that are suitable, and if not, perhaps you can recommend something elsewhere? Will not be used with underfloor heating, however may be there are some products normally used for underfloor heating that may be suitable in this application anyway.

    Kind regards,

    • Hi Adrian

      Thanks for your question. Unfortunately we don’t have any products that are suitable for this. The thinnest option we could suggest is 20mm of Thermafloor TF70 with 18mm of T&G chipboard over the top. Our technical team suggests that perhaps a gypsum fibreboard could be used? In any case, let us know how the project goes.

  24. We have a current floor of approx 20mm polystyrene and 18mm t&g chipboard (on concrete subfloor) which needs replacing. We can’t remove the skirting boards so don’t think we can sensibly get t&g flooring back in. Would 2 x layers 12mm ply laid in opposite directions and glued/stapled together floating over 20mm Thermafloor TF70 work?

  25. Hi. I wish to insulate my conservatory floor which at present is tiled 8″x8″ quarry type tiles and has a DPM under the slab.
    The floor appears to be reasonably flat. I’m going to use TF70 120mm and T&G Chipboard Flooring and Vynal on top of that.
    Question 1. Can I lay 120mm TF70 straight onto the tiles or will I need to use a levelling compound or Blinding Sand over the whole floor to get rid of the Grout lines?

    Question 2. Where I need to have a step by the French Doors will i need to provide timber to support the edge of the insulation and should the 18mm chipboard floor be fixed to this timber edge?

    • Hi Bob.
      A good couple of questions there.
      Answer 1. For the quarry tiles, you’ll need to ensure that the surface is flat and smooth by using a floor leveling compound. These are cheap and readily available from all merchants and are fully dry within 24 hours and are normally walkable on within 3 hours or so.
      Answer 2. Yes. You will need to provide timber support to the edge of the insulation. The guidance we give is that preservative treated softwood timber battens should be positioned at doorways, access panels and to support partitions. The size of the battens selected should ensure that, when installed, the top surface of the insulation boards are flush with the top of the battens. Yes fix the 18mm chipboard to this timber edge.

      I hope this helps. One final note is that after you install the insulation be careful to protect them from wheel or foot traffic by using scaffold planks or boards before you lay the T&G chipboard flooring.


  26. Hello
    I currently have a concrete foundation that im looking to put a DPM, then 100mm of TF70, then another DPM and then 22mm T&G floor boards. My concrete slab isnt very level though and I wondered if it was ok to put a layer of sharp sand on the concrete slab then a DPM and the TF70 on top of that?
    Thanks Simon

    • Hi Simon

      Thanks for your question. For a floating floor, a thin layer of cement / sand mortar can be used to achieve a level surface. With regards to the rest of your build-up, we suggest taking a look at the Thermafloor TF70 product brochure, which gives advice and guidance on how to install insulation below a floating timber floor – see pages 9 and 10 in particular.

      Hope this helps.

  27. Hello!
    Last year we knocked through our dining room wall into the garage, placing double doors into the new converted playroom. The garage flooring was solid concrete, which had to be raised up to the level of the suspended (concrete beams) house floor level. We have since noticed that there is a bounce in the chipboard flooring from the house-side in the door threshold. Is there any way to fix this? I imagine it’s where the concrete beams are not supporting the board.
    Many thanks for any advice,

    • Hi John

      Thanks for your question and your interest in our blog, however as this is not an insulation related query we aren’t able to advise unfortunately. Instead, we suggest that you contact a local builder or building control, who will be far better suited to answer your question.

  28. Hello,

    I am currently building a ground floor extension which will be a utility room and a WC/Cloakroom.

    The extension floor construction I am planning on is:-
    Porcelain Tiles 10mm thick
    12.5mm Tile backer board
    22mm T&G Chipboard
    Polythene separating layer
    100mm Kingspan Thermaflor TF70
    Thin layer of loose sand blinding or latex
    150mm Concrete Slab
    Polythen DPM
    25mm Sand blinding
    150mm Hardcore

    The uitility room will have a washing machine, tumble drier, under worktop fridge and and under worktop freezer.

    Will that floor build up be ok?


    • Hi Gary

      Your floating timber floor build up looks fine for a living room, bedroom, or similar.

      However, we wouldn’t usually recommend a floating timber floor under heavy applicances in a kitchen / utility room. Instead we prefer to specify insulation between timber joists.

      It might be worth consulting with a structural engineer to see what they think.

      Hope this helps

  29. I have a ground floor shop and wish to convert the upper two floors into a residential maisonette. The compartment floor between the shop ceiling and first floor must be 60 minute fire resistant. The existing floor is ex 25 pe floor board on timber joists lined on underside with 12.7 gypsum fire line board with joints adequately taped and filled. There is a 150 gap and then a suspended ceiling in the shop consisting of al frame with 600 x600 Armstrong Dune Supreme tile……sound absorption class E.
    Normally it would be easy to put another layer of boarding to the underside of the ceiling but the suspended ceiling is relatively new and very nice…..I could remove the tiles and slip the second layer of cut 1200×500 board in and screw fix, tape and joint fill? Obviously floating floor needed also but what is the spec? Can you help please???
    Incidentally I do have an existing burglar alarm system which can accommodate a fire alarm system also but that does not help me with the sound insulation which almost renders the fire resistance into second place!

    • Hi Michael, and thanks for your question.

      It sounds like you’re looking for fire resistance and sound absorption, rather than thermal insulation. If so, we’ll be totally honest – you’re probably be better off using a flexible insulation such as mineral wool, which could be placed within the suspended ceiling. Our insulation ranges between 15-20 dB depending on thickness, and mineral wool has a much better acoustic value. However, if you are able to fit insulation between the joists you could use Thermafloor TF70 for thermal performance.

      Hope this helps

  30. Hi

    I am in the process of fully renovating a house in Denmark. The national code for low energy emission housing is 400mm normal EPS of 0.041 to achive a lambda of about 0.08. Your calculator does not have that level of insulation in layer. Which was why I was hoping that 2 x 100 possibly fully glued with wood glue/white glue to ensure that the 2 layers does not shift. The thickness that I am after is 180/200mm which should give me the effect needed. the flooring will (top-down) be

    Floating wood floor (13mm)
    foam underlayment
    Damp proof membrane
    Kingspan TF70 200mm – glued)

    Is this glueing a way to go or do you offer it in 200mm thickness?

    Thank you in advance

    a floating wood floor on 22mm plywood

    • Hi Kenneth

      The thickness equivalent of 400mm of expanded polystyrene with a lambda value of 0.041W/mK is approximately 215mm of Thermafloor TF70. You would loose lay the insulation in a floor, no need to fix or bond, and it would need to be above the DPM.

      If you have any further questions, it would be best to contact our colleagues at Kingspan Insulation DK: http://www.kingspaninsulation.dk

      Hope this helps,

  31. Hi
    I am converting an attached carport into a bathroom and utility room. I will be putting a floating floor onto the concrete slab and would appreciate advice on a couple of points
    1 can the separating stud wall be erected on top of the floor or will it need to stand directly on the concrete slab, It would be much easier if it can go onto the FF as this will save on cutting of both the kingspan and T&G boards. Also I would be able to screw the base of the wall to the T&G.
    2 I have read that eg under the toilet should be on battens. Does this mean a ‘square’ of timber the size of the base of the toilet. Similarly how big should the batten be in doorways and under the likes of a washing machine. When I think of battens I think of the likes of 2 x 1 timber but this obviously would not be sufficient.
    Your advice would be very much appreciated

    • Hi Tony

      We suggest checking with a structural engineer as to whether the separating timber stud wall should be erected above the finished floor or from the concrete slab below it. However it is important to note that our insulation is not load bearing and cannot take structural loads.

      The compressive strength of Kingspan Thermafloor TF70, which you would use for a floating floor, typically exceeds 140 Kpa at 10% compression (1 Kpa = KN/m2) when tested to BS 826:1996. For a permanent loading figure we would quote a compressive strength of 28 KN/m2 at a maximum of 1 – 2 % yield.

      A floating timber floor has the tendancy for more movement than a timber joisted floor, so if there are expected to be heavy loadings such as kitchen appliances, it might be best to go with the timber joisted option shown in the Thermafloor TF70 product literature.

  32. I have a garden building which sits on 44mm tanalised joists above a concrete base.
    The flooring is 28mm tongue and groove boards. I would like to fit a laminate floor and wondered if this would be possible to fit over a damp proof underlay or would I need to remove the boards and fit kingspan between the joists directly onto the concrete (the concrete does not have a DPM).
    The problem with this is that the joists are only 44mm and the mimimum thickness of the kingspan recommended is 50mm?
    I am not very pleased with the company who delivered and installed the cabin as they have not been able to provide me with any advice on this.

    • Hi Christine, and thanks for your question.

      Ideally Thermafloor TF70 should be installed between timber joists, but this should be on top of a DPM. So if this is not possible the insulation needs to be laid onto a level substrate, with a minimum of 18mm T&G chipboard above and below the insulation to avoid point loading.

  33. Hi

    I am building a ‘man cave’ / games room in the garden. It has a 6m x 4m cocrete slab with a damp proof membrane. I want to put in a floating floor so was going to simply put TF70 on theconcrete, followed by 18″ chipboard T&G followed by whateber flooring I use.

    I would like to put a pool table in the room. Will the TF70 and chipbaord spread of weight be ok? Also what is the minimum depth of TF70 you would recommend? I would like the least amount of depth but for it to be strong enough for use.


    • Hi Jason

      It’s likely that Thermafloor TF70 under a minimum of 18mm T&G chipboard would take the weight of a pool table, but it would depend on how much weight is being transferred and the area of the feet. If you aren’t looking to meet building regulations, just use as much Thermafloor TF70 as you have space for below the chipboard.

      The compressive strength of Thermafloor TF70 typically exceeds 140 Kpa at 10 % compression (1 Kpa = 1 KN/m²) when tested to BS 826 : 1996 (Thermal insulating products for building applications. Determination of compression behaviour). For a permanent loading figure we would quote a compressive strength of 28 KN/m² at a maximum 1 – 2% yield.

      Have a chat with one of our advisors on 01544 387 382 if you want to double check anything.

      Hope this helps.

  34. Hi,

    I am currently converting my garage into two rooms a play room and utility area, the playroom will be a floating floor and i have read your comments i can lay chipboard straight onto the insulation, the gap that i am raising the floor by 135mm, the building control guy has suggested that i use cheap polystyrene then lay the kingspan on the top to reduce costs, would you recommend this?

    the other room is going to be insulated then screeded, i have to raise this floor by around 120mm what depth insulation would you recommend?

  35. hi hope you are well.

    i have a concrete floor with a carpet on top in my workshop (its attached to my house).
    i want to lay a battened floor (using 50mm thick battens) and 50mm ga4000 between the battens, then put 18mm chipboard t and g on top. .i believe i need to batten because ihave some reasonably heavy point loads (a workbench or two)…id rather not batten but im paranoid about these things.

    i want to screw the battens to the concrete.

    ive been advised to lay a dpm, but given that it only has carpet on at the moment and isnt damp, do i need to do this?

    if i do need a dpm, how am i supposed to attach the battens to the floor without compromising the dmp?

    finally – do i really need to use battens??

    thanks guys and merry xmas!

  36. I have 225mm polystyrene insulation boards that I want to lay onto soil inside an outhouse between strip foundation and dwarf walls.
    Can I do this instead of concrete screed?
    Plan is
    225mm insulation then timber joists above the insulation to carry 22mm chipboard.
    I intend to use the building as a summer house, with mixed usage.

    • Hi Steven, and thanks for your question.

      Our rigid foam insulation is not load bearing so it should not be used as floor substrate instead of concrete. However Styrozone can be installed below concrete and below a damp proof membrane.

      Hope this helps.

  37. Hi
    Great website: very informative. Thank you.

    Am planning to build floating floor for wooden workshop on 4″ concrete slab (has DPM) using 18/22mm moisture resistant T&G chip on moisture barrier on 70mm TF70.
    How long should I wait for concrete to dry out?
    I will have a couple of heavier bits of machinery in workshop: I was thinking of supporting their base area on battens ripped to 70mm, lying side by side with TF70, under the chipboard. (Rather than go to the effort and expense of building a full frame of 16″ spaced battens). Does that seem reasonable?
    Sorry, prob stupid question but is the 70mm Kingspan exactly 70mm thick?
    Thanks & regards

  38. Hello,
    against my better judgement I am going to ask:
    would TR26 insulation (120mm) be ok to use instead of TF70 for insulating solid concrete floor?
    Due to the change of plans (courtesy of my local council) I have found myself with lots of TR26 120mm boards left over.
    Since we will need the same thickness insulation to insulate our ground floor I was hoping to utilise thermaroof on the floor.. are there any dangers in doing so?
    Many thanks!

    • Hi Marius

      The compressive strength of Thermaroof TR26 LPC/FM would be able to cope with loadings of a domestic floor so there would be no ‘dangers’ as such to the insulation itself. However, we have not tested the product in this application and therefore would not recommend it. There may be issues with a warranty provider or building insurer as the product has no third party approval to be used in a floor application.

  39. Hi – I plan to lay a floating garage concrete floor over 100mm TF70. The buildup is: structural reinforced concrete slab, DPM, TF70, plastic vapour control layer for decoupling, then 120mm of C35 concrete with A142 mesh and UFH pipes, finished with power floating.
    The heaviest vehicle will be a 4×4 which exerts about 25psi(170 kPa) at the contact points(tyre). Obviously the force will be well distributed by the slab above so will a compressive strength of 140 kPa be adequate for the insulation layer?

    • Hi Chris,

      With regards to the compressive capabilities of Thermafloor TF70 we can confirm that this product typically exceeds 140Kpa at 10 % compression ( 1 Kpa = 1 KN/m² ) when tested to BS 826 : 1996 ( Thermal insulating products for building applications. Determination of compression behaviour.) For a permanent loading figure we would quote a compressive strength of 28 KN/m² at a maximum 1 – 2% yield. Please consult a structural engineer who can determine whether or not this product is suitable for your proposed application.

      Hope this helps,

  40. Hi

    chipboard floor (22mm)
    Separation layer (500 gauge polythene)
    Insulation Kingspan TF70 100mm
    Damp proof membrane 1000 gauge
    Concrete slab.

    would the above spec be suitable for refurbishing a bedroom floor containing large king size bed and two free standing wardrobes
    I’m not keen on using timber batten I have had problems with damp in the past.


    • Hi John

      The specification is acceptable in terms of build-up, however we cannot state the U-value achieved by this build-up without the P/A ratio. The P/A ratio is the area (m²) divided by the exposed perimeter (the lengths – in metres – of any walls around the floor that face externally or into a cold space, added together). Once you have this, use our free online U-value Calculator to gain the U-value.

  41. Hi
    I’ve just had all of my laminate and sub flooring removed due to flooring on ground floor. The insulation was 20yr old thick compacted polystyrene balls with the bosrds on top. I love that the room has gained 3″ in height and wonder if I can kerp it like this (or as near as possible) by using any of your products? The base is concrete with a membrane underneath and it had one on top. Sorry Im a technically and construction challenged demale lol!

    • Hi Al,

      This would depend on the exposed perimeter and area of the floor, the U-value requirement, and whether you are using screed or concrete on top of the insulation. We would recommend contacting Technical Services to discuss on +44 (0)1544 387 382.


  42. Hi, I have currently a new timber floating floor installed in a stone 2 storey house and well vented , because of it being a stone house I was advised not to use a dpm or radon barrier directly onto the floor as any dampness could find its way to the walls and rising damp could be an issue.
    I am considering the following make up.
    Stone base
    Douglas Fir timber joices raised off the floor
    TF70 between the joices
    Radon/dpm on top of the insulation
    Plywood flooting
    Laminated flooring

    I am a bit unsure if I should be scrapping the radon barrier for a breathable membrane as I don’t want a condensation build up either. Could you point me in the right direction please.

    • Hi James

      As long as the void beneath the timber floor structure is fully ventilated, there should be no issue with condensation forming to the underside of the floor as the airflow will carry out any residual moisture. The membrane used between the insulation and plywood topping should be a polythene separating layer, usually around 1000 gauge, similar in performance to a vapour control layer.

      Hope this helps.

  43. Hi, I have a carpeted floating floor in the ground floor of a 1997 Beazer Homes house. There is 22mm glued T&G chipboard over insulation described as polystyrene. I’m not sure what the construction is below the insulation but the foundation is concrete.

    The floor has developed movement and lots of creaking in the middle of each room, close to rear sliding garden doors, and in the hallway. It is firm along partition walls.

    Can you suggest what the cause of the problem might be and how I could rectify it using kingspan panels & timber battening if necessary? I wish to remove carpets and lay engineered T&G oak boards. I would like to do this at the same time as building a small extension, with flooring continuous into the extension.

    thanks for you feedback

    • Hi Ben

      It would be difficult for us to diagnose the issues here, and as an insulation manufacturer it would inappropriate for us to speculate. If you wish to relay the floor either as a timber floating floor or with insulation between joists, we would recommend the use of Thermafloor TF70. The literature I have linked to contains information on both a floating floor and installing insulation between joists. Please contact our technical team on 01544 387382 to obtain a U-calue calculation to specify the thickness of material required.

  44. Hello

    I’m moving into an old house with existing wooden (floating) floors. Rather than lifting them all can I simply put floor insulation over the top then ply and a real wood floor? Appreciate will need to change the skirting and plane the doors but this is so much cheaper than lifting insulating and reinstalling a new floor!

    • Hi Claire

      As long as the insulation is being laid onto a dry, even and structurally sound substrate, the suggested floor construction will be suitable. We recommend the use of Thermafloor TF70 for this application, using a polythene separating layer between the insulation and the plywood topping.

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