ph: 0845 053 2800
GREEN STRUCTURAL ENGINEERING LTD
www.greenstructeng.co.uk
info@greenstructeng.co.uk
OUTLINE METHOD STATEMENT
PROPOSED EXCAVATIONS / 19 ILCHESTER PLACE W14 8AA
UNDERPINNING / BASEMENT LEVEL EXTENSIONS
PROPOSED SUBTERRANEAN DEVELOPMENT
GENERAL PRE-CONSTRUCTION NOTES
1. All excavations to be carefully undertaken in order to avoid damage to existing structure & foundations.
2. All services to be located and clearly identified prior to excavation for new foundations / underpinning.
3. Contractor to provide detailed method statements outlining proposed construction methods, sequence of
construction, temporary works arrangements and access / storage arrangements prior to start of
underpinning. This package of works to be undertaken once the successful Contractor has been
appointed.
4. Concrete underpinning / retaining walls to be carried out in max 1m lengths equally distributed along the
perimeter length, such that the maximum length of wall left unsupported at any time must not exceed one
pin bay length in any one length of wall to be underpinned.
5. Sequence of underpinning to ensure at least one bay length between work in progress and a completed
pin, unless it is a closing pin bay.
6. Where necessary walls may require lateral support above ground prior to underpinning. This support
must be submitted in the method statement.
7. If required sacrificial sheet propping to support the earth face may be used prior to pouring each underpin. Appropriately rigid styrene filler may be employed at the earth face of the pin to form the void under
existing masonry footing plays and above any outer toe in the pin.
8. If the contractor finds anything, circumstance or condition, not in accordance with the drawings, the
engineer is to be informed.
SEQUENCE OF CONSTRUCTION
1. All excavations to be carefully undertaken in order to avoid damage to existing structure / foundations.
2. Sequence of underpinning to ensure only one pin bay is open at any one time in a wall length, and one
pin bay distant from a completed pin bay, unless a closing pin bay. This must be clearly indicated in
diagrams accompanying the Contractors method statement.
3. Excavation for each bay (refer to above) to be carefully undertaken down to new formation level, and
excavated material temporarily stock piled / removed off site as expressed in the Contractors method
statement.
4. Concrete to be placed as quickly as possible after completion of excavation for each bay.
5. Reinforced concrete underpinning / retaining walls and bases to be carried out up to within 50 - 100mm
of the underside of the existing foundation, with dowel bars provided between adjacent pours (bent as
necessary to suit excavation sequence), in order to provide suitable bond between adjacent bays.
6. Reinforcement to concrete underpins to include starter bars between new RC bases (to underpins) and
slabs, to allow for positive connection to RC slab (constructed at a later stage).
7. Temporary horizontal props to be provided and maintained between opposing walls / underpins, in order
to ensure adequate lateral restraint prior to construction of basement / ground floor slabs and or such
other construction whereby the permanent works provide the lateral restraint.
8. Recently placed concrete to be left to set and shrink for two days before a 1:3 sand:cement dry mortar
packing is rammed into make full contact between the old and new work. This shall be allowed to set
over one day.
9. Remove face and side shutters.
10. Upon completion of all underpinning required as per structural design, new basement to be fully
excavated to formation level.
11. Concrete blinding layer to be constructed and slab reinforcement laid prior to construction of reinforced
concrete basement slab.
12. Waterproofing and finishes to be applied in accordance with the Architects specification.
Registered Office: 21a Fabian Rd, Fulham, London, SW6 7TY
Registered in England Number 06533911
GREEN STRUCTURAL ENGINEERING LTD
www.greenstructeng.co.uk
info@greenstructeng.co.uk
ph: 0845 053 2800
SOIL CONDITIONS
To support the attached CMS we can also confirm that we have already successfully completed subterranean
developments in the vacinity. It should also be noted that No15 Ilchester Place have successfully completed
deeper excavations within the last 5 years. From trail pits dug we can confirm that ground conditions are
generally consistent with the geological records and known history of the area and compromise made ground
some 2m in thickness underlain by deposits typical of River Terrace Gravel with extended down to the full
depth of the proposed excavations.
DESCRIPTION OF 19 ILCHESTER PLACE AND ADJOINING PROPERTIES
The property is part of a large post war brick terrace of two story with roof space forming a third floor. It is
of masonry construction with timber floors and roof. The property is in excellent sound condition
structurally. The neighbouring properties are of similar construction and look to be in sound condition from
an external non-intrusive visual examination. A number of adjoining properties have already carried out
subterranean developments.
CONSTRUCTION CALCULATIONS
Please rely on enclosed detailed drawings as being produced by way of calculations. Please note all
information submitted is subject to copyright Green Structural Engineering Ltd.
CONSTRUCTION DRAWINGS
See attached appendix. Please note all information submitted is subject to copyright Green Structural
Engineering Ltd.
NEW CONSTRUCTION
1. Contractor to provide all necessary temporary propping (via adjustable steel props / needles, flying
shores etc), suitable to ensure stability of walls, floors / structural elements over, prior to removal of
existing walls. This package of works to be undertaken once the successful Contractor has been
appointed.
2. Engineer or architect to set out extent of rear room.
3. Commence excavation in a 1m wide strip, at 1m depth install sheet piles to the sides of the trench with
acrow props to restrain these. Continue excavation to formation level dropping the sheet piles as the
excavation deepens. Ensure sheet piles are toed into ground. Additional acrows should be installed to
the trench sheets as the excavation deepens.
4. Spoil to be removed via conveyor through the house to a skip. This will be emptied when skip is full.
5. Form respective layers under the new slab to levels given by engineer or architect.
6. Lay mesh reinforcement for slab and erect shuttering to form kickers for the walls. Ensure walls have
starter bars from slab.
7. Pour slab and let cure.
8. Install reinforcement in the walls ensure continuity between starters and wall reinforcement. Erect
shuttering to form walls.
9. Pour section of wall to approx 1.8m and let cure.
10. Repeat steps 8 and 9 until full height of wall is reached.
11. Repeat process in 1m strips until the rear basement room slab and walls are formed.
12. Erect shuttering for top slab.
13. Lay reinforcement for the top slab. Pour slab and let cure.
14. Strike shuttering and remove all materials.
15. In a similar fashion form rear light well.
Les Harris C.Eng, MICE, MIStructE
Green Structural Engineering Ltd.
Registered Office: 21a Fabian Rd, Fulham, London, SW6 7TY
Registered in England Number 06533911