Mark... Why did you have to go down a mega 6 feet. Is that got something to do with the height of the build.
Ah well, once you understand the purpose of a footing it becomes clear, it also helps explain why many conservatories and some poorly built extensions 'move'
What your trying to do is get to firm and undisturbed ground at a level below where external influences such as tree roots, water and frost can have an impact.
Frost in the UK is not to bad but the ground saturation can vary quite a bit and hence why the minimum is usually 900mm.
In my case, the house was built with very deep footings as its on a slight gradient (the virgin ground at the front of the house would have been about 600mm deeper than the back) so they dug a deep footing of the same depth all round and once built, back filled the area to bring the ground level up.
Consequently I had to dig through circa 500mm of the finest dark peaty soil (our top soil) and then it was onto about 1m plus of in fill which was clay, brick and any old crap (I was unearthing some hand made bricks from Coalville brick works!). This stuff was hard, very hard and required a mattock to get through it after which was a layer of peat which also had to come out and hence the final depth.
Interestingly, the final depth is 400mm plus less than the depth of the original house footings (as they are deeper than they need to be at the back).
So with a foundation, in summary, you are looking for frim undisturbed ground and with this you can build up to three stories high......but you still need to meet this requirement even for a conservatory (but sadly they rarely do!)
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Topic: A bit of homework, Project E (Read 37647 times)