Structural Report
On the Proposed Basement at
7 Tregunter Road
London
Kensington & Chelsea Council will only permit basement & underground
developments that do not:

Cause harm lo the built and natural environment and local amenity

Harm the Amenity of Neighbours

Loss of Open Space or Trees

Result in flooding

Lead lo ground instability.
The properly in question is an existing 4 storey, semi-detached property with a
basement.
The existing lower ground floor will be altered and extended at the front to create a
bigger space
The general construction is masonry load bearing external walls with internal timber
studwork. The lower ground floor consists of a ground bearing concrete slab with
concrete underpinned walls.
Superstructure
The superstructure proposed work will include the reconfiguration of the internal
spaces on all floors as well as a small front extension at lower ground floor level.
Substructure
The substructure proposed work constitutes a new basement under the front garden
of the property. The front and side of the basement retaining walls will be below the
existing front wall of the property and the far side will accommodate a rear light well
and stairs which will lead to the top of the rear garden.
The basement will be constructed in reinforced concrete retaining walls underpinning
the existing external walls.
Bridges Pound Ltd has extensive knowledge of the design and construction of new
basements.
The proposed method would be subject to detailed contractor’s proposals but a
normal sequence would be:
l. Excavate front to allow for conveyor to be inserted.
2. Form 'front of basement' with cantilevered retaining walls
3. Slowly work from the front to the rear of the extension inserting 1200 long
cantilevered retaining walls sequentially.
4. Cast ground slab
5. Waterproof internal space with a drained cavity system.
The underpinning would be designed to carry all imposed loads required plus the
highway loads to the front.
As the party walls are to be underpinned this would normally leave the party wall with
a deeper fooling than the neighbours other walls, and the design will look at the
available bearing capacity. As part of the Party Wall agreement a precondition
survey will be carried out.
However in this instance both properties have identical basements so the effect of
deeper footings and the potential differential movement has been negated.
From the site investigation reports on an adjacent development the ground
conditions showed the presence of gravels and ground water to be at some 6-9m
depth. With these free draining materials the hydrology of the site should remain
unchanged from its present state.
However the gravels will require earth support measures during the underpinning
phase of the project.
Conclusion
In this instance due to the small nature of the basement extension, and the fact that
both properties will be have exactly the same basement configuration, we believe
there will be no harmful impact on the properties from these works.
The ground conditions as stated early would suggest that the area is free draining
and again there is no significant risk to the surround hydrology.
S.Fowle BSc(HONS) M.I.Struct.E C.Eng
Bridges Pound Ltd