Antony higo Posted November 18, 2019 Share Posted November 18, 2019 Hi all. I'm having a new concrete floor put in my cellar. The house is pretty old (1917). I'll be getting a local builder to do the main concreting work but wanted to do most of the prep. work myself to save money. I'll be digging it out. Putting hardcore, sand and a membrane down. My questions are how far down do I dig? Was thinking 8/9 inches. How many inches of hardcore? How many inches of sand? And where do I put the membrane (under hardcore, under sand or on top of sand)? I know next to nothing about stuff like this so any help is much appreciated, cheers. Link to comment Share on other sites More sharing options...
PeterW Posted November 18, 2019 Share Posted November 18, 2019 Welcome. Any chance you can dig another 4 inches and get some insulation in there ..?? One option is to even just use 50mm of Polystyrene insulation instead of sand before the DPM as it’s both good for insulation properties and also means you don’t need to use a sand blinding. Link to comment Share on other sites More sharing options...
Antony higo Posted November 18, 2019 Author Share Posted November 18, 2019 I've seen something (on YouTube) about putting insulation in. Is it just normal kingspan insulation board you use or special stuff? I would have thought kingspan would crack under the weight of the concrete. Or just soak into it. Are you saying if I use this I can just put it over the hardcore then put the membrane on top? That does sound like an easier option. Thanks. Link to comment Share on other sites More sharing options...
PeterW Posted November 18, 2019 Share Posted November 18, 2019 Depends what you use and if the room will be heated ..? If it is, you need a minimum level of insulation in the floor. I tend to use 25mm Jablite instead of blinding, then the DPM, and then Kingspan/Celotex as the lower layer is more pliable and accepts the stones etc. even where it’s been compacted with a whacker plate. 1 Link to comment Share on other sites More sharing options...
Bitpipe Posted November 18, 2019 Share Posted November 18, 2019 Not exactly the same but we built our basement slab on EPS 200 grade - the number after the EPS is the point load bearing capacity of the insulation in N/m2 (I think). EPS is also more water resistant than open cell insulation (like XPS). You would be able to get away with a lower grade - we have an entire basement, foot thick RC walls, plus house sitting on our EPS just figure the loading per m2 Not sure in your case whether the membrane needs to be under or over the EPS but if it's butted tightly together then the concrete will not run down into it - we had the membrane on the top of ours and the EPS sat on a sand blinding layer on a base of compacted type 1. 1 Link to comment Share on other sites More sharing options...
Antony higo Posted November 18, 2019 Author Share Posted November 18, 2019 (edited) 2 hours ago, Antony higo said: Edited November 18, 2019 by Antony higo Repeated Link to comment Share on other sites More sharing options...
Antony higo Posted November 18, 2019 Author Share Posted November 18, 2019 The room will have a radiator in. It's just going to be used as a play room for the kids. Might be a silly question but what is Jablite? Link to comment Share on other sites More sharing options...
Ed Davies Posted November 18, 2019 Share Posted November 18, 2019 2 hours ago, Bitpipe said: the number after the EPS is the point load bearing capacity of the insulation in N/m2 (I think). kPa (kilopascals = kN/m²) so 1000 times. But that's the loading for 10% compression which is a bit much. For more realistic 1% compression it's about 1/3rd to just under half that: https://sandbeps.com/wp-content/uploads/2018/02/Floors-datasheet_2018.pdf For context, a 1 kg [¹] object has a weight of about 10 newtons (actually closer to 9.81 N) on the surface of the Earth. EPS200 has a safe working load of 90 kPa for 1% compression so that's nearly 9 tonnes per m². [¹] kg measure mass, not weight. Link to comment Share on other sites More sharing options...
Ed Davies Posted November 18, 2019 Share Posted November 18, 2019 1 hour ago, Antony higo said: Might be a silly question but what is Jablite? It wouldn't be if there was no way to search the web for sites like: https://www.jablite.co.uk/ and https://www.insulationsuperstore.co.uk/browse/insulation/insulation-board/floor-insulation/jablite-insulation.html 1 Link to comment Share on other sites More sharing options...
Antony higo Posted November 18, 2019 Author Share Posted November 18, 2019 Just seeing that there are different types of hardcore. Any idea which kind is suitable for this job. Thanks. Link to comment Share on other sites More sharing options...
Russell griffiths Posted November 18, 2019 Share Posted November 18, 2019 Not meaning to be a killjoy here is this already a habitable room i really don’t like the idea of a kids playroom in a cellar, is there another means of escape in a fire ? i may be barking up the wrong tree but would hate for anybody on here to advise that this is a good idea without knowing more facts. Link to comment Share on other sites More sharing options...
Simplysimon Posted November 18, 2019 Share Posted November 18, 2019 plenty of reading to be had here http://www.nhbc.co.uk/Builders/ProductsandServices/TechZone/nhbcstandards/ Link to comment Share on other sites More sharing options...
Antony higo Posted November 18, 2019 Author Share Posted November 18, 2019 It's not a closed in cellar with only one exit. Our back door opens into our back garden (house is basically 3 floors). Entry/exit through kitchen too. 1 Link to comment Share on other sites More sharing options...
Russell griffiths Posted November 18, 2019 Share Posted November 18, 2019 19 minutes ago, Antony higo said: It's not a closed in cellar with only one exit. Our back door opens into our back garden (house is basically 3 floors). Entry/exit through kitchen too. In that case you could do with digging down further and getting more insulation in the floor, the extra insulation is relatively cheap, it’s the digging down that’s a pain, whats the headroom like ? Can you go up instead of dig down. Link to comment Share on other sites More sharing options...
Antony higo Posted November 18, 2019 Author Share Posted November 18, 2019 Height of roof is 83". Going up isn't an option really. How deep would you recommend Russell? Would I have any issues regarding the foundations? Link to comment Share on other sites More sharing options...
Russell griffiths Posted November 18, 2019 Share Posted November 18, 2019 The more insulation the better, but obviously every job is different you probably need a chat with your builder, or do a test hole and see what you have there now. 1 Link to comment Share on other sites More sharing options...
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