Removal / replacement of concrete floors.

11/03/2011 - 18:56

Hello,could the forum give me advice on the following.With our old house renovation we have to dig out the ground floor ,this is to comply with the floor ceiling height regulation.My question is, would they include a plastic membrane across the whole floor area to stop moisture/damp and then the concrete floor on top,as we do in England? Would this be the same in Italy and do they have a building regulation for this type of work?



This really is something that you need to talk to your architect or Geometra about - they will know what your Comune will approve, and do the relevant drawings that will need to be submitted for approval. Things to look out for [in no particular order]:-

  • You should have a strong membrane bedded on sand or similar on which you cast the slab
  • slab should have some reinforcement in it to prevent cracking
  • solid insulation panels [say 100mm thick] on the membrane before concreting will improve insulation
  • if digging down - don't undermine the existing walls - on older properties, the foundations may not be very deep [if at all]
  • bring the membrane up the wall to above about 100mm above ground level - stops water ingress
  • Check if you need any drainage under the membrane to cope with groundwater

As I said earlier - get professional advice - you'll need it Alan

Thanks Alan,have emailed with my geometra and the stubbling block seems to be putting in the membrane.He says that any ground water will be taken care of with land drains around the outside of the house,internal work to include  everything you have said but no mention of the insulation or membrane!Thats why i wondered if a building standard existed for this type of work? 

In reply to by atessa

I'm not at all certain of the 'letter of the law' on this one, but usually the assumption is that you will have a 'ventilated' ground floor. The modern way of doing this in your situation is to dig out the ground floor to about 250mm below finished floor level, lay some 'iglu' on the clay or rock revealed, throw 100mm of reinforced conc over the top and then tile it. These 'iglu' are plastic crab like structures (also known as granchi) which simply isolate the concrete slab from the substrate and form a passage (ventilated) for any rising groundwater from springs etc. It's an okay system if you don't have the depth to do a proper 'suspended' ground floor. The old UK solution of using a membrane can work - except (depending on your geology) it can also mean that around the edges of your 'waterproofed slab' you might get some lovely fountains! The 'big issue' as alanh has alluded to is about undermining your existing walls. This is why the least deep solution is chosen - but if you have to dig down even the minimum of 250mm you still might face this difficulty.

No mention of under-floor heating.!!!  If you want some degree of efficiency you'll need it ... the future is all about heat pumps and these run very efficiently on UFH because they don't have to push the heat so far uphill - so to speak. No doubt Badger can explain.

I had to "laugh" when I saw this thread. When our builder was carrying out the exercise he was also digging down to get rid of the traces of cattle urine etc as it was an old stable on the gound floor. He hurriedly called us over to Italy one weekend to show us that the walls of the house ended up finishing about 3 feet above the level he had dug down to and with no foundations although I couldnt understand his surprise bearing in mind it was at least 100 years old!   Inevitably this resulted in great deal of time and expense underpinning the walls and inserting a seismic "skirt" around the perimiter. So be warned!

Am currently working on floors using this system. Fast and easy to lay, steel reinforcing on top and then concrete. Also ventilate the floor to the outside (under the igloo ) to help prevent the damp rising through the existing wall structure.  If you do go for underfloor heating, you need the slab first, then the insulation and UFH pipes, then the new floor screed. Take that all into account for the final floor height.

Thanks Fillide and Badger,the web site was very useful, now know what igloo is,never heard of this before,also noticed scudox this was used to isolate any damp around the outside walls, included with the land drains.Inside the geometra  could not dig too deep,he did not want to disturb the old foundations.I should also say that the house is on the level and is not in a very wet area.

We had igloos installed during our renovation.  We also had to reinforce the internal walls with large metal plates either side of the walls and bolted together. We explored the other options available - mini piling, v expensive; building retaining walls either side, unsitely. The metal plates, (20) weren't cheap but are now concealed behind the intonoco.   We asked for grey water recycling and under floor heating.  The architect and builder 'forgot' to allow the required depth. So we said goodbye to the water recycling but stood our ground for the UFH. We have a wall that is halfway underground due to an earthbank. Again, the architect wanted the most expensive, chemical solution for damp-proofing. We researched, and discovered Delta membrane which is used in tunnel manufacture, cellars etc. ours goes on the outside of the wall and is fastened with special clips.  You can have the option of special drainage if you have groundwater probs,(or fix it internally). Then the earth and stones were piled back and covered with earth. Touching wood, after 4 years it's perfectly dry.  Only prob I've found with igloos, is they make the rooms echo-ee.

Hi, I am a builder working here in Italy and in my experience you have to install the igloo and ventilate to the outside. The minimum height igloo you can use to have a recognised ventilated floor is 15cm, this can help with shallow foiundation depth. Good Luck! Tony