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hi i am about to self build a single storie exstension on the rear of my house . i have no idea to what depth and width the footings need to be? the two side walls are 2600 in length and the front wall will be 6400 thanks mike
Hi Mike,
To answer you fully I would require to know loadings to the foundations or what the walls will consist of : ie brick / block single/ double skin cavity /timber kit etc..
Generally your foundations will be minimum of 450mm below ground level for frost protection and minimum 150mm to 200mm thick concrete with a compressive strength of 35KN.
Width of foundation will be = wall thickness + 100mm external and 100mm internal for scarcement.This also helps with minor set out errors. Building control officers will frequently insist on new foundations at same dimensions and levels as that of the existing structure.
Ensure your excavation is compacted relatively level and free from laitance ;ie loose clay and dry if possible prior to pouring concrete,they may also require blinding concrete which consists of a 50mm layer weak concrete laid through the excavation prior to concrete foundation being poured.NB. Check for all buried services before excavation. If you require more info please follow up.
Regard's
Bill
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| Comment | thanks for the knowlegde i can now commence wit the build | ||
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Answers by Expert:
Bill-C
Expertise
Questions on UK construction from Setting out Projects through to completion. Mainly concreting ,drainage ,bricklaying, masonry,carpentry and decorating,plaster work ,render/roughcasting.From new build construction to historical restoration, renovation. How to set out ,levelling and survey matters.
Experience
Timeserved bricklayer , developing to Construction Site Manager and Educated to Site Engineer.
Having been in the Industry for 35 years carrying out all types of general construction . renovation and historical renovation and remedial works.Now mainly on luxury dwellings to the value of £2M.
Having been self employed and advising main Contractors and Developers through Construction phases and managing the works from concept to completion.Having a broad spectrum of experience.
Education/Credentials
Scottish Apprenticeship in the crat of bricklaying.
Scottish Construction Industry Site Managers
Site Civil Engineering Construction and Surveying Set out.
Scottish Civil Engineering Analysis of Concrete and Mortar
Asbestos encountering.
Scaffolding Inspectors Certification
Planning, Programming and Management
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