Hello everyone, I am a brand new member and would appreciate some insight. I am building our family's custom home here in the Greater Toronto Area of Ontario. It will be a two-storey house with a finished basement, and the planned footprint is approximately 2000 square feet. After demolishing the 80 year old bungalow on the lot, our excavation team encountered high water table and soft silt soil, so the soil engineer made us dig till we reached firm soil, approximately 2 feet deeper down. We had to trench and pour concrete to create what is called a 'mud slab', a process that delayed us by more than a few days.
Eventually, footings were laid down over this uneven mud slab and now ICF blocks are being stacked over it to create the vertical walls of the basement.
Sorry, could not attach photo as the allowed limit is very small.
Besides costing more money in excavation, poured concrete (which is in essence a foundation for our footings) and then shoring the sides of the site, we have constantly run water pumps to keep the excavated site free of water. A particularly rainy spring season has not helped, but the water seems to maintain a steady level in the excavated site, the rain does not seem to cause a heavy flood, which tells me this is groundwater that will persist for the future and must be addressed now for a dry basement for the foreseeable future. We are using experienced ICF contractors (and there are not that many) and even they were worried with how much groundwater there is.
The 20' x 20' garage will have a suspended AMDECK slab and we plan a media room below it and this area is almost 24" below the rest of the finished basement floor, so a sump pump here is a given.
Besides the mud slab, there are two perforated steel barrels buried in half a truckload of coarse gravel each with filter cloth filtration system, which is where we locate our submersible pumps and run them each morning for about 2 hours to dewater the site.
After the city inspector viewed the footing forms before concrete was poured in it over the now set mud slab, he strongly recommended a drainage and 'water management plan' below the basement slab, besides the perimeter drain system being installed. He recommended the same soil engineer should design it who knows the site well.
We wish to do this right so we never have to deal with a wet basement.
1) How do you go about this water management process below the slab, besides the outer perimeter drain?
2) Should we use a brand name prefabricated system or let the contractor do what they usually do?
3) One sump pump was certain, now I am thinking maybe two more?
4) A radon mitigation membrane is needed for our city, how does this interior drainage work with this thick poly?
Any and all feedback is welcome, and I thank each one of you for reading my long post and sparing your time. Much appreciated. |