Foundations and underpinning
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We would refer you to our article on the different types of foundations and the history of the foundation. See links at the bottom of this article.
The forces going down must equal the forces going up
It sounds obvious when you say it, but the forces going down must equal the forces going up, otherwise the property will sink. Therefore, you need to ensure that your foundations need to be sitting on solid material, normally known as the bedrock.
The type of foundation must be appropriate for the type of ground
We have a vast range of different types of soils and sub-strata's in the UK and the foundations need to be built appropriate to their load bearing capacity. Building on peat tends to get structural engineers nervous, as it progresses, and building on clay gets them even more nervous, as it expands and contracts. Over the years man has become very ingenious on building where they want and has come up with solutions for most ground conditions.
How to build on clay soil
Today if you were building on clay soil you may be required to use form of clay board, such as a polystyrene board, although this holds the weight of the concrete when it is wet, which can be heavy, it will compress when under extreme pressure, i.e. when the clay gets wet and heaves (expands) the polystyrene compresses and the clay can expand without causing any/too many problems. Unfortunately, for people with older properties, this has not been around for too many years and we were involved with its predecessor, also known as a clay board, that was literally two layers of hardboard with egg box cardboard in between. This was laid underneath the floor slab with a plastic sheet over it. Unfortunately, condensation got into the plastic sheet and when the concrete was poured it collapsed, meaning we had to pour a great deal more concrete, but more interestingly, meaning that the gap wasn't there. Having visited the property many years later it doesn't look to have caused any problems.
Common problems found in clay areas
In the 1970's it was fairly common to have a 600 wide by 300 deep concrete foundation. These can crack as the clay heaves. A contributory factor towards this can be where the original foundation is not cleared out properly, where the concrete was poured it was onto a wet and sloppy surface, which meant the clay had contracted (clay is at its optimum when it has 40% to 60% moisture, above this it becomes liquid-like, below this it becomes powder-like).
Is underpinning a solution to foundation problems? Let us start by explaining what underpinning is. This is where a foundation is put under the existing foundation, the idea being that it gives extra support, the reality is often different.
Problems with underpinning
This brings us onto the problems caused by underpinning. Yes, we did say problems caused by underpinning. Often underpinning has been used as a solution in the past for problems, but we would argue it has caused an equal amount of problems. Partly, this is not because of how it is specified, but because of how the work was carried out. In years gone by contractors tended to be paid on how much concrete they laid, rather than laying the right amount, so a great deal of concrete was poured! Also, the use of partial underpinning seems to be a problem, as, in our opinion, this adds a great deal of weight to one part of the building, making it a lot more rigid than the part that is not underpinned. The two parts of the building are therefore going to act differently.
Think before you agree to underpinning
Many insurance companies offer underpinning as a solution. Just take care when accepting this, although it is nice that an insurance company has offered to do some work, as we do understand the problems in getting them to do work! Unfortunately, you only understand how good or bad your insurance company once you have actually asked them to pay out for a problem you have had! Insurance companies, in our experience, are driven by a one-off quick fix solution rather than a long term solution and, indeed, we have experienced where an insurance solution, for example, to underpin where there was a tree problem resolved the effect, i.e. the settlement of the foundations, rather than the cause, which was the tree, and it would have been far better to have managed and maintained the trees and perhaps put a root barrier in place if problems had still occurred. So, when it is suggested by the insurance company that the property is underpinned just check that it is in your best interests as well.
Please see our section on: Specific Defects Reports
If you truly do want an independent expert opinion from a surveyor with regard to structural surveys, building surveys, structural reports, engineers reports, specific defects report, dampness issues, dilapidations, home buyers reports or any other property matters please contact 0800 298 5424 for a surveyor to give you a call back.
If you have a commercial property, be it leasehold or freehold, then you may wish to look at our Dilapidations Website at www.DilapsHelp.com and for Disputes go to our Disputes Help site www.DisputesHelp.com .
We hope you found the article of use and if you have any experiences that you feel should be added to this article that would benefit others, or you feel that some of the information that we have put is wrong then please do not hesitate to contact us (we are only human).
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