Consulting Structural Engineers and Surveyors

Construction Method

Statement Sample

Client Ref: 123457

For

Location xxx

Consulting Structural Engineers and Surveyors i

Structures Made Easy Limited South Ealing Road

London

W5 4RL

Telephone: 07525 047778

E-mail: support@structures-made-easy.co.uk

Principal: xxx

Consultant: xxx

© Copyright Structures Made Easy Ltd.

Unless explicitly stated otherwise, all rights including those in copyright in the content of this document are owned by

or controlled for these purposes by Structures Made Easy

Except as otherwise expressly permitted under copyright law , the content of this document may not be copied,

reproduced, republished, broadcast or transmitted in any way without first obtaining written permission from the

copyright owner.

Location xxx

Consulting Structural Engineers and Surveyors ii

1. Scope of Work 1

2. Property type and proximity to other properties and trees 1

3. Soil Condition and Ground Investigation 1

4. Planning drawings with Construction mark up 2

5. Design Philosophy 2

6. Construction Sequence 3

7. Prevailing ground conditions & adverse risks 4

8. Surface Water run-off 4

9. Appendices 5

Location xxx

Consulting Structural Engineers and Surveyors 1

1. SCOPE OF WORK

This Construction Method Statement (CMS) is produced for submission to the London

Borough of [borough name] in relation to a planning application at [property address],

for a front and rear basement extension.

The CMS is only to be used for this purpose and may not be reproduced and used for

any other property without the express permission of its author, without which, no

liability for the accuracy of the contents contained within can be granted or guaranteed.

2. PROPERTY TYPE AND PROXIMITY TO OTHER PROPERTIES AND TREES

The property is a mid-terrace dwelling arranged over 3 floors above ground level with a

partial lower ground floor. The property is constructed in solid brickwork (no cavity) with

suspended timber floors above basement under a slate covered traditional cut and

pitched mansard roof.

There are no trees in the vicinity of the proposed excavations that would normally

constitute further design considerations in accordance with B.S.5837:2012 ‘Trees in

relation to design, demolition and construction – Recommendations’.

The adjoining property at [neighbouring property address] has very recently carried out

a full excavation of the front and rear garden areas to form a new lower ground floor

throughout the property.

3. SOIL CONDITION AND GROUND INVESTIGATION

The existing ground conditions are noted from the British Geological Records as being

Kempton Park Gravels overlying London Clay.

Location xxx

Consulting Structural Engineers and Surveyors 2

No formal trial pit or borehole log has been carried out at the property given the

prevailing conditions whereby there is an existing basement and no obvious hydro-static

ground water problems manifest in the existing basement area.

Additionally, no pump system was used to enable the excavation to the adjoining

basement at [property address] further reinforcing our opinion that the level of the

water-bearing strata is below the excavations and intrusions.

4. PLANNING DRAWINGS WITH CONSTRUCTION MARK UP

Architect drawings [drawings number] show the existing and proposed basement

layouts.

Structural drawings [drawings number] show the underpinning sequence and retaining

wall sequence and sections.

5. DESIGN PHILOSOPHY

The basement design will be carried out following relevant statutory design guidance in

the British Standards, namely: B.S.8102:2009 ‘Code of practice for protection of below

ground structures against water from the ground’; B.S.8004:2015 ‘Code of practice for

foundations’; and B.S.8002:2015 ‘Code of practice for earth retaining structures’.

Steelwork support for the existing superstructure will be designed to B.S.5950-1:2000

‘Structural use of steelwork in building. Code of practice for design. Rolled and welded

sections’.

Reinforced concrete retaining walls and underpinning will be designed to B.S EN 1992-1-

1:2004+A1:2014.

Design loads will be calculated in accordance with B.S.6399-1:1996 ‘Loading for

buildings. Code of practice for dead and imposed loads’.

Location xxx

Consulting Structural Engineers and Surveyors 3

6. CONSTRUCTION SEQUENCE

1. Excavation will commence at the front of the property with arisings being removed

by ‘grab lorry’ on a daily basis. When complete, excavation will continue at the rear

of the property with arisings being moved from rear to front by small Bobcat

skidsteer machine and/or wheel barrow. The arisings will be lifted from basement

level to ground floor for removal using a mechanised conveyor belt.

2. The new retaining walls 1-5 are formed in sequence so that the back of the

excavation can be utilised for supporting the back props until the last wall is

constructed. Wall 5 will be propped using a sacrificial thrust block cast into the base

below the drainage runs to support the inclined props supporting the shutter

forming the wall.

3. The existing walls to be retained will be underpinned as necessary using traditional

methods in a ‘hit and miss’ sequence as outlined on SME drawing [drawing no.] with

underpins typically 1000mm width. Each underpin must be 48 hours old before dry

packing. After underpin 3 is formed and dry packed a further 72 hours must pass

before excavating for the last underpin 4 is excavated in order to preserve the

structural integrity of the other underpins and the party fence wall above.

4. Each underpin is formed using a base and stem. The base is cast first then the stem

with continuity reinforcement supplied to tie the two elements together and

laterally.

5. Dry packing 75mm thick will be carried out in a specific time sequence to each

underpin as outlined in a specification accompanying the underpin installation

design to ensure structural stability of the property is maintained throughout the

operations.

6. Temporary Works (TW) design to support the front and rear party fence walls and

footpath will be designed by a qualified Engineer and followed as excavation

proceeds to full depth. Lateral support props will be incorporated at specific depths

of the excavation in line with the TW Method Statement.

7. The retaining walls will be formed in elevational sequence with starter bars to

connect to the adjacent wall subject to the TW design.

8. The basement slab will be designed to provide lateral support to the finished

retaining wall base.

9. Propping for basement wall removal and back propping for ground floor alterations

and new steelwork will then be carried out and completed prior to the next item.

Location xxx

Consulting Structural Engineers and Surveyors 4

10. The sump pump chamber and below slab drainage for both foul and surface water

will then be installed to correct falls leading to the existing main sewer connection

for foul and surface water.

11. The new basement slab will then be constructed with soft joints formed around each

drainage pipe before pouring concrete.

12. The waterproof membrane will then be applied to the slab and walls in accordance

with the warranted design for the membrane and immediately covered with the

appropriate level of rigid insulation to protect against damage and for thermal value.

13. The correct thickness of screed will then be applied including any underfloor heating

provision to the required floor level prior to applied floor finishes.

7. PREVAILING GROUND CONDITIONS & ADVERSE RISKS

Where the ground is found to be stable, excavations can proceed in accordance with the

TW design and method statement. Ground water should not present a problem given

the absence of hydrostatic ground water arising in the existing basement; however,

should ground water ingress occur, a sump pump must be supplied and discharged into

a skip or other receptacle to first permit silts to settle before the pumped water is

allowed into the below ground drainage system.

The primary risk comes from inadequate propping during underpinning and wall

removals by not following a clearly defined methodology for Temporary Works.

Selection of a suitably qualified and competent contractor is essential combined with

professional supervision by the relevant designers.

8. SURFACE WATER RUN-OFF

The existing impermeable areas at the front and rear are not materially increased by the

construction of the proposed extended basement and therefore do not constitute a net

increase of surface water run-off to be considered in design.

Location xxx

Consulting Structural Engineers and Surveyors 5

9. APPENDICES

Prepared and approved by

[SME Consultant]

1 3 4 2

1 3 4 2

Beam

over

Beam

over

Beam

over

Beam

over

Beam over

New

Column

New

Column

Sacrificial Thrust Block

Proposed Basement

Neighbour's Garden Level

Patio Level

Sub-strata to be passed as suitable byLABC prior to commencement of the work

Existing wallWall to be properly propped during construction

Underpinning Section

300

Well rammed in dry pack

RC Retaing wall

Wall Section

300

Structural Details

A3

Contact:-· Support@structures-made-easy.co.uk· www.structures-made-easy.co.uk

17 PARSONS GREEN LANEMS Sample

MS Sample