......or not.
Entry posted by vivienz
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Chance meetings, research and no fear of being nosy have stood me in good stead for many years and it's proving no different with getting a house built. The 'dig deep' thing was bothering me, mainly the thought of having to go down 2m over the entire footprint of the build and the cost of all that muckaway, as well as the risk of it all turning into a giant, muddy swimming pool during the process. I will freely admit that up until about 10 days ago, the thought of having to get piling included in the build struck terror into me due to what I perceived as the potential cost and complexity involved, all down to my own ignorance about piling. As a new comer to the world of self building, the only thing I'd really picked up on in the past was hearing about remedial work to houses that were falling down and the huge amounts of cash involved.
I'd already had a mooch around this site to see what I could see on the matter of piles and had a look at @recoveringacademic's blog and his comments and rapidly lost my fear but not my trepidation over costs. I also had a visit to the build site of another BH member who has been very helpful and encouraging. It was a spontaneous visit as I was really, truly just passing by his site on the way to my own, but his structural engineer was there at the time so I stood quietly by and ear-wigged, as you do, and then one thing led to another and we started chatting about my site and my clay dilemma.
The upshot is that the SEs were really helpful guys and I'm engaging them to design a piling system to support my MBC build and overcome the risk of both lateral and vertical movement that my site is very vulnerable to. I'm also having them design the drainage system while they're at it. They will liaise with the architect, building control and the timber frame company and make sure that my build not only gets out of the ground but stays in the same place once it's done. I've never had an issue with professional fees as long as they are ones that are genuine and add value to a project. In this case, it will be money very well spent and a huge weight off my mind. How best to approach the drainage plan had been vexing me for the last few weeks, particularly as my clay soil means that soakaways don't function.
One thing that I think may be worth mentioning is the combination of the passive slab and a piling system. The soil beneath the building is not just highly shrinkable clay, but also very dessicated thanks to the long term presence of a few trees and a super thirsty hawthorn hedge. Although these are all now gone, their long term potential affect on the soil will remain for a long time. In particular, the risk of heave. The piling system will keep the building in place, but does nothing to stop the swelling of the clay directly underneath from pushing up and breaking the floor of the new structure. The SE started to talk about a suspended floor to mitigate against this. However, a few days ago I read a BH discussion where @JSHarris mentioned the issue of an airgap under a passive slab having a detrimental affect on the insulation of a slab so was able to say with some confidence that I wanted the slab to rest on the ground, and my reasons why. The SE was fine with this and all the gubbins under the floor will now include a layer that is a honeycomb structure with the face of the cells resting on the ground so that if it does expand, it has somewhere to expand into without damaging the slab.
The helical piles are part of an impressive system - no piling mat, no excavation if you don't need it (I need some to make sure that the floor level of the house is level with the ground), super quick to install and little vibration. This will save a huge amount of time and money compared with digging deep and a far more elegant solution with the dangers of heave solved as well. In all, the cost of the SE and the piling won't cost me any more and it may be somewhat cheaper. The time element is important, too, as the lesser amount of excavation will be much speedier and keep me on track for the main part of the build to take place from end of May onwards, assuming everything else is ready.
The cherry on the cake was put in place this morning with full discharge of all the pre-commencement planning conditions. All in all, a good week.
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