Y:\Projects\8819-ms-001

METHOD STATEMENT & SEQUENCE OF WORK

TO CONSTRUCT BASEMENT STRUCTURE

SITE ADDRESS: 57 BRONDESBURY ROAD, LONDON, NW6 6BP.

PROJECT REF: 8819

Ref. to Dwg. 8819/SK01.

Underpinning

Excavate the individual bay to be underpinned to the new formation level.

The soffit of existing foundations is to be thoroughly cleaned and cut back to a sound

face before concreting and dry packing.

The existing corbelled brick foundations will be carefully cut back to the wall line on

the internal face. Extra precaution is to be taken in excavating further to allow

underpinning and bay widths are to be limited in width (1 max) or permanent props

installed.

Adequate temporary supports are to be provided where walls are to be underpinned

and arching of brickwork is deemed not to be present or brickwork not sound. Steel

prop supports shall be inserted locally if necessary after excavation beneath the

foundations and shall be bedded on the approved formation and concreted into the

underpinning.

Concrete to be GEN 3 (20 N) mass concrete uno.

The sequence of underpinning is to be agreed with the Engineer before proceeding

with the work. Each bay including excavation to be 1m wide maximum and to be

sequenced in conjunction with a sequencing plan drawing. Typically a 1-5 numbering

system for bays is provided for construction. Works to be sequenced to maintain

adequate foundation support to the building at all times.

Excavate and cast bays marked 1. Allow 24 48 hours to cure before dry packing.

Allow 24-48 hours to cure before excavating the subsequent bay.

Excavate and cast bays marked 2 and dry pack as above.

Repeat for 3, 4, 5 until underpinning complete, or similar sequencing (Note:

sequential ordering for bays in a length of wall is 1st bay, 3rd bay, 5th, 2nd, 4th and

so on, such that a subsequent bay is not located adjacent to a most recently

constructed bay uno).

Y:\Projects\8819-ms-001

The width of the underpinning base at formation level is to equal the width of the

existing brickwork foundations.

New Basement RC Retaining Wall Horizontal Restraint

Adequate temporary horizontal supports are to be provided to replace the horizontal

restraint the existing floor currently provides to the foundations during the works.

The permanent horizontal support is by means of a new internal basement RC

retaining wall constructed of reinforced concrete. This internal retaining wall provides

horizontal restraint up to the foundations. The walls and base are to be constructed

of 150mm thick reinforced concrete. Walls to be poured against the mass concrete

underpinning to the level of the existing floor slab. The base is to be constructed off

of 50mm level and compact blinding. Concrete to be grade RC40.

During construction adequate temporary horizontal supports are to be provided to

the head of the retaining wall as required where the floor is removed or the base not

fully constructed at all times.

New Basement Floor Slab

The new basement floor slabs are to be of ground bearing nominally reinforced

concrete construction. Slabs to be 150mm thick with A142 mesh in the centre of the

slab. Concrete to be grade RC40.

This report assumes a competent contractor is appointed to undertake the works.

Killian OReilly

Gurney Consulting Engineers