11 Nov 2008

On Eco Slab

This is me at the Harrogate Homebuilding & Renovating show standing on an Eco Slab.

What is an Eco Slab? Well, I hadn’t seen one before but the fact that it was being demonstrated on the stand of Logix, one of our best known ICF suppliers, gives you a clue. Because what ICFs are to walls (i.e polystyrene moulds), Eco Slabs are to floors.

• You level the hardcore base
• You cover the floor with 1m square eco slabs, which have little polystrene legs
• You then pour a re-inforced concrete slab. The thicker the concrete, the wider the achievable span.

Will it catch on? I’m not sure. What you end up with is a hybrid which is not quite a solid slab (because there is air beneath the eco slab) and yet not quite a suspended floor (because the legs of the eco slabs rest on the ground). Does it require ventilation, as a suspended floor would? Not sure. And if not, then why not just build a solid slab? Off to the website to find out more but the website just shows up as a blank page in all my browsers, which doesn’t inspire confidence in the company behind it.

But it certainly supports a 15 stone blogger, and his Costa Coffee latte.


  1. Hi Mark,

    I checked the web site for "Eco-slab", www.thermaflor.com, which came up fine on my browser.
    The literature we gave out refers to the Thermaflor website, which is currenlty being updated, and the whole product is undergoing a re-branding exercise to make better use of a name that links to one of its key benefits. Hence the currently blank Eco-slab.com website.

    The product can be used either to create a suspended slab, by using reinforced concrete which bears on the walls, or a ground bearing slab, with a fibre reinforced concrete topping.

    As the suspended floor, once the concrete has set the EPS is only formwork and insulation, and does not contribute to the structural design. Yes, as a suspended slab it does have to be ventilated, like all suspended slabs, and the legs provide enough room for air to pass freely under the floor.

    Eco-slabs use as a ground bearing floor is less common, but it can providing a practical way of ventilating the space under a slab to allow the escape of radon and other gasses.

    I hope this makes things a little clearer.

    Jonathon Barnett, Logix UK

  2. It is a great idea, however I note that at the wall/floor junction there is still a significant cold bridge. Can you have the slab/eps 'floating' from the wall, so that a vertical section of insulation can be installed against the wall, 'breaking' the cold bridge?
    What happens if you want to go to higher levels of insulation - at what location in the build up can you install extra insulation?

    It does also make me wonder when a company uses the wrong term (it is embodied energy, not imbedded energy) whether their 'eco' claims are properly understood.... :)

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  4. Well I have used this product in three houses and the point is it is a ground supported but ventilated system. So not only do you get high U-values that can easily be made higher by putting additional insulation over the DMP before you pour but it means you can satisfy Radon and contaminated land issues easily through ventilation. As it is ground supported the floor wall union can be insulated to prevent a cold bridge with screed hiding the edge insulation. The product is dry and light easy to work and then you just flood in the concrete. Not hard to understand is it?!

  5. Hi guys
    this seems no different to just casting reinforced concrete on sheet eps. If you want a suspended slab then the better option in terms of span performance would be a beam and block system with an eps block infill.(Jetfloor?) You dont then need hardcore or infil material and the structural floor is only 150 deep for up to 5m spans
    and U values down at 0.15 or lower.

  6. Looks good but can't really see the point of the voids. However, the real question it raises with me when, in terms of eps density and thickness, might we reach a balance point such that no concrete is needed? Can EPS of the right density and thickness take full successive floor and roof loadings, perhaps with only thin steel or nylon ties from roof to ground slab to resist wind loading.
    Perhaps someone at Eco-Slab is clever enough to work that out?