One week on

It is one week since my last blog and I have to report that nothing much has changed. Work on-site has basically stopped while the Structural Engineer considers a rafted solution to the problem. I spoke to him yesterday, and he promised to give me an update today, but he has not done so. This is all really quite disheartening.

I have asked the Groundworks Contractor to spend a little time exploring the rest of the area with his digger as I want to know the exact extent of what we are dealing with. i.e. where does the "good" rock end, and the "soft" stuff start. We cannot afford for another change of plan - this time it has to be right.

Jan has done some research on the web, concerning other options to a concrete raft. She found some companies that do "Ground Compaction". The idea is that the existing material is compacted in such a way as it forms a pile of it's own. However tentative enquiries have indicated that this would not be cost effective in a domestic setting. It is a technique designed for large scale works (e.g. roads or factories). In fact one of the companies described how they use a crane to hoist a 120 ton weight 25m into the air and then let it drop ! Sure, it will compact the ground, but I think the house, and probably all the neighbour's houses would end up as piles of rubble at the bottom of the hill !

Another company (www.uretek.co.uk) do foundation reinforcement using some form of pumped expanding foam, but really is that any more environmentally friendly than concrete ?

Speaking to my Dad yesterday, I got some more feedback from his neighbour Ted. Ted liked the idea of a concrete raft - in fact he was all for jumping in his car and coming up to help me lay one myself ! Maybe I am being unnecessarily pessimistic ? It still concerns me that the heaviest part of the raft will be on the soft ground, while the lightest part is on the rock. Also, how is it going to integrate with the existing building ?

Dad also mentioned his friends who live in Essex. They had to have their house demolished and rebuilt as a result of subsidence. Their new house is supported on 15m (yes, fifteen metre) concrete piles, poured into a compressible liner into pre-drilled holes. Even these piles do not reach bedrock, but at this sort of length, the friction alone along it's length is enough to carry the ground Bearing Pressure (they are, not surprisingly, called Friction Piles). Anyone who has tried to bang in a fence-post will have experienced a small scale Friction Pile. I have spoken to the Groundworks man here about drilling but apparently it is not very easy in this area. The ground - especially when "made up" as in our case - contains too many stones. The drill sees these as a false bottom. Drilling is only successful in fine soils.

One final thought is that the ground Bearing Capacity of the ground will need to be less, if the weight of the building on top of it is reduced. To this end I filled in the online form of "Welsh Oak Frame" (http://www.welshoakframe.com/home.html) to see if an oak framed extension with some form of paneled in-fill might be a lighter option than stone and concrete blocks. It would have to go through a complete replan phase with the council, but hey, it is an option !