Basement construction

tipperary

Currently at the OPP stage of a self build project, and considering the various options for the final building. Due to the sloping nature of the site we are considering a kind of half basement, i.e. basement at ground level to rear of house but buried to front of house. What are the usual methods for this construction? Are there any precast options available?

Johnniep

Concast do precast retatining wall system, however, due to the amount of joints etc, it would be extermely difficult to get it watertight! Depending on the retained depth and the nature of the ground, you would probably best going with a reinforced concrete solution, or possible a reinforced block system.

Mellor

The joints wouldn't be a problem, it just just need to be tanked (externally), like all retaining walls below the watertable.

A contigious or secant wall might work also, and would provide support for ringbeam/walls. although it might be an expensive option

galwaytt

in the immortal words of the internet........ DAMHIK !!

Viking House

Are you insulating the basement on the outside and is there any insulation under the tank?

iei044775

I have a house 60% complete that had a situation identical to what you have described. I poured a reinforced concrete wall with concrete waterproofer (Kryton-Kim) http://www.kryton-ireland.com/ in the foundation and wall. And then built a cavity wall inside the concrete wall, it will be insulated like the rest of the house, pumped insulation. After a very wet winter no water or dampness has penetrated the wall.

Picture from Last October attached.

Evieweavy

If I were going to use a precast option I'd construct the retaining wall and then construct your block walls inside it at a set back say 150-200mm and I would put a drainage channel (or a perforated land drain) between the 2 to allow for drainage then I would construct my inner leaf of blockwork inside this again. To be honest I'd do this with either precast or cast insitu, retaining walls. House basements are very difficult to waterproof not least because of the lack of experience of the builders in dealing with the materials typically used in waterproofing.

tipperary

thanks to everyone for your input. Having investigated further, I am now considering the use of ICF for the basement. Does anyone have any experience of using this as a basement construction? I am curious as to the methods of waterproofing the structure. Am I correct in assuming that the radon barrier under a raft foundation could be returned up the walls, and then lapped with a waterproofing membrane on the walls?

Evieweavy

What's the raft for? What are the site conditions a very wet site with a high water table obviously isn't ideal for a basement and you would need a waterproof concrete design I'd run a mile from ICF and stick with traditional insitu if that is the case. As an aside watch out for ICF suppliers some have absolutely no technical know how which I experienced recently. As for the DPM it depends on the detail for your raft. Typically walls are built off strip foundations and so there is a break between the wall and the ground floor slab which you would pass the DPM through but there are different details for raft foundations, sometimes a suspended floor slab is used sometimes the dpm is lapped around the slab ask your engineer or architect what they envisaged.

golden

Evieweavy, What is you reasoning for running a mile from ICF basements?

Pataman

Be careful if using ICF, the thickness of the poured wall might not be strong enough to support the house above. Suppliers may quote a 300mm block, however its generally only 150mm thick concrete and the rest is ICF. If you are cosidering a basement, you really should have an engineer on board.

The void in ICF can be made to any width as required for the structural strength of the wall and reinforcement bars are installed as required.

Exactly the same as any other cast in situ concrete system, the only difference being is that the formwork remains after the concrete has been poured.

golden

Thanks for that were at planning stages and looking at all options hopefully including a basement if the co co clears it.