A trial hole is usually dug near to the proposed location for the extension. It will safely expose the existing foundations confirming the depth, width and type of the existing foundations. The building inspector may be asked to record this information and discuss the proposed foundations for the new extension. We make every effort to design every element of the building work in order to remove the delays that can cost time and money on a building project.
There is however no guarrantee that this will be the depth when the foundations are being dug out. When the agreed depth has been reached the building inspector can increase the foundation depth until a good strata has been reached. Other factors that can influence the foundation depth and or type is the location of foul or surface water drains, type size and position of some trees, water table and soil type & conditions and contamination.
When necessary we may recommend that a bore hole is carried out to establish the type of strata present at various depths in the ground where the extension is to be built. The bore hole is typically provided to a depth of 10M. A bore hole with basic soil testing will cost around £1200. When soil samples are taken and appear to be contaminated with fossil fuels such as petrol or oil these samples will need to be tested for the amount of the contaminents present which typically costs an additional £450 per sample tested. During the process soil samples can be taken and tests carried out for water table or soils types present etc. Usually, these are controled by our structural engineer who will discuss the tests required during the time the bore hole is carried out.
If your soil is of poor then a piled foundation may be the answer and in these situations our structural engineer will produce the deisgn
and calculations for the piles and ground beams. The drawings will be issued to the piling contractor to design the diameter of the piles and the overall loadings for each pile. On a small single
storey extension of 3M x 3M we typically charge £2,800 for the design and calculations of the piles and ground beams.
Without approved structural design and calculations we can only estimate the cost of the piles and ground beams on your project. When these drawings are approved we will provide a fixed price quote.
Room-By-Room (UK) Ltd
Watton at Stone
Tel: +44 1920 424280
Mb: +44 7814 146779
Alternatively please use our contact form.
Monday-Friday 9.30 - 16.30
Site visit 10.30 - 14.30
Initial / first meeting hourly rate reduced by 10% to £90.
RESIDENTIAL / EXTENSION
Initial / first meeting free of charge within a 5 mile radius of Hertford, Hertfordshire