In this week’s property surveying party wall blog post, we are going to be discussing trial pits, when they are applicable, and the purpose behind having a trial pit undertaken.
A trial pit is required if the building owner, who is the owner undertaking the construction works, is undertaking excavations in close proximity to a neighbouring structure.
The pit itself is a controlled excavation/dig, and will ultimately see a small test hole dug, usually 1m x 1m, or large enough to allow for a workman to safey dig the trench/pit, with the depth of the pit/trench being to the underside, or depth, of the adjoining owner’s foundations.
Once the underside of the foundations are determined, the building owner’s team will have an exact understanding of exactly what the depth and profile of the neighbouring foundation is. They can then take that into careful account when designing the building owner’s proposed works.
The engineer’s role will be to look at issues such as the interaction of the proposed foundation and existing, ultimately ensuring the risk is as low as it possibly can be.
With this type of scenario, whereby an existing or proposed structure are in very close proximity to one another, the building owner will likely also find themselves having to dig their proposed foundations in sectional ‘hit and miss’ bays.
We have written another blog post on sectional hit and miss bays, that you can locate on our website. We would suggest having a read of that.
They also have to install a slip membrane which will effectively separate the existing foundations and proposed foundations from one another, ultimately ensuring that the two foundations don’t get bonded, or toothed together as a result of the new works taking place.
Trial pits are usually a bit of a pain for a building owner, as they likely require excavation work and construction work taking place in advance of the actual project commencing, so for this reason, a lot of owners find it to be something they would rather not action.
It is worth bearing in mind that the very purpose of the excavation is to arrive at a controlled understanding which will ultimately ensure that the party wall surveyor’s time spent on the matter is as low as it can be, and ultimately that the risks to the adjoining owner’s property is likewise the same.
If you would like to discuss party wall procedures with us, or perhaps you’d like to discuss your neighbour’s party wall proposals with us, give us a call today, and we will be more than happy to assist you.
