Potential Plot Problems

You have been granted planning permission and all of the impeding issues that are associated with it have been dealt with it. At this stage it is a good idea to start assessing the quality of your plot, because this will dictate the type of foundations that you will need to lay and this will impact on your budgeting and timescale costs.

If your plot of land is standard and there are no obvious issues with it, then you can expect to pay around £10 per square ft (maybe a little less); however, if you discover something that is a little out of the ordinary you will pay more to rectify it, maybe even 3 or 4 times more.

Things that could increase your foundation costs

Below are some quick pointers of what to look out for when assessing your development plot, and if you uncover any of these you can be expected to increase your foundation budget because there will either be more digging required, or you will need to lay specialist foundations necessary for your particular issue.

Your plot may have been used as a dump

If when you look a little closer at your plot it looks like the ground has been disturbed previously this could indicate that your plot may have been used as some kind of dump. This is not a good sign, and at best would mean extra digging to remove the dumped material (which you will then need to discard of in a proper manner), or at worse your land may have become contaminated and you will need to take the correct cause of action to deal with this.

Is your plot contaminated?

Owning a polluted plot of land is something you want to avoid, because it will undoubtedly lead to build delays, paperwork, and extra costs and headaches. This is why is it good to avoid plots whose history points to it being used to house some kind of industrial building, or it has been used as a tip. Both of these previous uses for your land can mean it is now impregnated with a cocktail of toxins, which could include a mix of chemicals, heavy metals, and gases. Normally, depending on the type of contamination you have, there are 2 standard solutions. You can either lay down clay or concrete and create a tomb and encapsulate all of the nasty toxins, and this is enough to prevent any potential later problems and will keep the local authorities happy, or you can dig out all of the contaminants, take them to a specialist location, and then burn them. Of course this all depends on the kind of contamination you have on your plot, and would need an expert to check over your land if there is any evidence of a past that could lead to such issues.

Are there old foundations on your plot?

If there is evidence of previous old foundations on your land it will suggest that either a building once stood where you want to build, or the foundations were laid down but for some reason the build was terminated. If a standard general purpose building was once on your plot the chances are that things will be ok, and you can simply dig out the old foundations and then put down your own. However, if a previous build was terminated is could suggest there were additional issues discovered by a previous developer that meant it was a good idea for them to simply more on and leave this plot. It could always just mean they ran out of money of had other personal issues, however you should investigate this further before you accept or dismiss a particular plot of land.

Old drains and wells

If there are a network of drains that zigzag under your plot this will almost certainly mean you will have to undertake extra investigatory work and lay down non-standard foundations. You will have to call a specialist engineer to look over your land and do some tests, and this will set you back at least £150, and probably more because you will need to organise the hiring on diggers on a lot occasions (for around an extra £80 or so). The same issues arise when old well are hidden out of sight and partially filled.

Digging pits and bore holes

Ideally you will not need to dig your land before you want to lay your foundations, but if there is the potential for huge extra costs and delays because of unexpected underground issues then if may be better to know about them before you really begin to ramp up you building process. You will likely have to dig trial pits or bore holes if you choose to investigate the quality of your plot.

For trial pits you do not dig exactly where you will then go and lay your foundations, but you will dig the hole pretty close to its location. The hole will be around 10 ft (3 metres) deep, and after it is dug the specialist engineer will analyse the quality of the ground (normally just by visually looking into the hole and also the unearthed soil), and then the hole is filled in. If you cannot dig out a trial pit (normally because it is difficult to get a digger to the correct location), then bore holes are an alternative option to assess the quality of your plot. You’ll need 2 of these auger bore holes, and these require specialist machinery that, as you might expect, force a coring tube into the ground and when they are pulled out bring up a consistent core of earth. Again, the engineer examines the removed earth before the cores are replaced to fill in the holes.

Other potential plot problems

As well as contaminated land you should look for high water tables and poor drainage on your plot, which can be identified by spongy feeling ground and confirmed by excavation investigations, such as the trial pits and bore holes discussed above. Also, look for trees within close proximity of where your foundations will go, because these could have strong and wide spread roots that can damage foundations, or they could cause issues with overhanging branches and other planning permission issues in the future. Finally, if your plot lies on a large slope, typically more than a gradient of 1:25, this will require extra work to lay the foundations, and will add extra costs to your build budget.


It will be relatively rare that you cannot lay some kind of foundation for your build; however, the difficulty and therefore cost of the foundation work can be very high if straight forward, non-standard foundations and excavation work is needed. It is therefore always advisable to at least check over your plot, and maybe even get a qualified building inspector to give their opinions, before you start building work (or even buy the land in the first place). Here we have mentioned the most common issues that can arise when you are laying foundations, and are issues you should always be aware of. If it is almost certain that you will need specialist foundations without even digging trial plots of bore holes, then it may actually be a better option to just save your cash and simply dig out your foundations and assess the situation as you go along, rather than dig trial holes in some other part of your land. If you only have suspicions, or there is a chance you will pull out of your build if non-standard foundations are needed, then trial investigation are probably a good option.

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