Soil Classification and Footing Recommendation Report

Soil Classification and Footing

Recommendation Report

JOB NUMBER:

S50436 - 271472

CLIENT: CLIENT REF:

Glenvill Homes Pty Ltd 43945

SITE:

6 Allie Street, SURREY HILLS, VIC, 3127

DATE:

31/07/2020

REVISION:

0

Glenvill Homes Pty Ltd Page 2 6 Allie Street, SURREY HILLS, VIC 3127 31/07/2020

FMG Ref: 271472-S50436

PREPARED BY:

QA BY:

Jack Bjelopavlic, Civil Engineer Angelo Demangos BEng (Civil) (Hons) MIEAust RBP Residential Technical Manager Victoria

FMG Engineering

P 03 9815 7600 F 03 9815 7602

[email protected] Level 1/2 Domville Avenue, Hawthorn VIC 3122 fmgengineering.com.au


FMG Ref: 271472-S50436

Table of Contents 1. Introduction .......................................................................................................................... 4

2. Fieldwork and Site Conditions .............................................................................................. 4

3. Site classification ................................................................................................................. 4

4. Footing recommendations .................................................................................................... 5

4.1. Precedence of Design Information ................................................................................... 5

4.2. Piers .................................................................................................................................. 5

4.3. Bearing Capacity .............................................................................................................. 6

4.4. Waffle Raft ........................................................................................................................ 6

4.4.1. Site Preparation ..................................................................................................... 7

5. Special notes for construction relevant to this site ............................................................ 7

5.1. Windspeed Assessment Classification ............................................................................. 7

5.2. Flexible Connections ........................................................................................................ 7

5.3. Articulation ........................................................................................................................ 8

5.4. Site Drainage .................................................................................................................... 8

5.5. Sewer/Easement .............................................................................................................. 8

5.6. Tree Effects on Soil Moisture Conditions ........................................................................... 8

5.7. Removal of Trees and Rehydration of soils 9

5.8. Existing Structure on site 9

5.9 New site investigation required 10

6. Potential construction difficulties ........................................................................................ 10

6.1. Soft Soils ......................................................................................................................... 10

7. Other important information about this report ..................................................................... 10

7.1. Variations from the Report .............................................................................................. 10

7.2. Future Tree Planting/Landscaping .................................................................................. 11

7.3. Foundation Maintenance ................................................................................................ 11

7.4. Important Notes to the Owner(s) .................................................................................... 11

8. Provisions .......................................................................................................................... 12

8.1. Property Owner ............................................................................................................... 12

8.2. Design – Management - Quality ..................................................................................... 12

8.3. Copyright ........................................................................................................................ 12

Attached Documents

• Borelogs

• Site Plan (borehole location)

• Site Photos

• CSIRO Notes (Owner’s copy)


FMG Ref: 271472-S50436

1. Introduction

FMG Engineering has been commissioned to carry out a Site Investigation and assessment of

subsurface conditions at, 6 Allie Street, SURREY HILLS, VIC 3127. The purpose is to determine

the Site Classification and minimum founding depths for an articulated Double Storey masonry

veneer building proposed on this site in accordance with AS2870-2011.This report is not

suitable for use for basement construction or if a cut of more than 500mm is undertaken,

further testing would be required if this is the case.

For the purposes of this Report, the Property Owner is defined as the person or persons

whose name(s) appear on the Certificate of Title for the site.

2. Fieldwork and Site Conditions

In preparing this report FMG Engineering has made the following observations.

• At the time of sampling the site had a fall.

• Trees were observed next door, on the street verge & on site.

• Fill was observed up to 600mm deep on site for the boreholes undertaken, however deeper fill may be present. In addition, fill may be deeper when holes are backfilled after removal of trees and house on site.

• An existing house was present.

The approximate soil test borehole locations are shown on the Site Plan attached.

Three (3) boreholes were drilled using a hand auger to the depths as indicated on the

borelogs. The samples obtained were logged and then classified in accordance with

AS1726 and AS2870.

Details of the observed subsurface conditions encountered have been recorded on the

borelogs attached.

The Geological Survey Maps showed the site to be underlain by Silurian Aged Sedimentary

Deposits and associated residual soils. In general, the anticipated subsurface conditions

have been encountered during this site investigation.

3. Site classification

Free swell ys values, calculated in accordance with AS2870-2011, are shown on the

borelogs. The maximum ys (characteristic surface movement (mm)) value calculated at this

site is 22mm. The site was classified 'P' to account for:

• Abnormal moisture conditions caused by the presence of a tree/s which may affect footing performance. Refer to Section 5.6 for further details.

• The maximum yt, potential surface movement due to tree induced suction change (mm)) value calculated at this site is 32mm.

• Disturbance of natural soil due to the removal of existing vegetation/trees and the demolition of the house.


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It must be emphasised that in classifying this site, FMG Engineering did not place sole

reliance on the soil borelogs as a means of being an absolute representation of all

subsurface features existing at this site.

Relevant information and guidance used in classifying this site has been taken into

consideration and is tabled below:

1. The broad experience of FMG Engineering.

2. Well established and relevant local knowledge of the general behavioural characteristics of

foundation soils in the vicinity of the site.

3. Specific soil reports and classification on adjacent sites which were referred to.

4. FMG Engineering’s vast experience relating to past performance of existing structures in

the general area.

5. Published geological maps.

6. State-of-the-art publications by Standards Australia, Australian Geomechanics Society and

The Foundations and Footings Society (Vic), Practice Notes

7. Engineering assessment of the likely characteristic surface movement (ys) based on

estimated Ipt values as noted on the borelog. Ipt’s are based on Shrink Swell tests (Iss)

carried out in a laboratory on the same or similar soils to this site.

8. It can occasionally be difficult to distinguish between natural SOIL and FILL during testing.

4. Footing recommendations

Selection and performance of Footing systems

AS2870-2011 provides details of 'standard' footing designs for each site classification (A, S,

M, H1, H2 and E). The structural sizes and reinforcing requirements for these standard

designs increase as the 'reactivity' of the site increases, from A (least reactive) to E

(extremely reactive). These standard designs include a stiffened raft slab, strip footing

system, and waffle raft slab.

AS2870-2011 implies that the performance of each of these standard designs should be

approximately equivalent for a given site classification, and hence the footing system may

be selected on the basis of design constraints (including site characteristics), builder’s

and/or Property Owner’s preference, and/or economical considerations.

4.1. Precedence of Design Information

Where the final design details and site preparation recommendations documented by the

Design Engineer are at variance with the recommendations contained in this report, the

Design Engineer’s details shall take precedence.

4.2. Piers

Piers are required to ensure footings are founded on B horizon Sandy Clay natural soil.

Bored piers need to be founded 300mm into the B horizon Sandy Clay.

Piers are required to alleviate the abnormal moisture conditions that is expected to be caused by trees.

Piers that are used to mitigate abnormal moisture conditions within the radial zone of tree root influence should be founded a minimum of 2700mm or to rock, whichever is shallower.


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Back Hoe Piers:

300mm wide x 1200mm long

Bored Piers 600mm diameter

4.3. Bearing Capacity

All external ribs must penetrate any uncontrolled fill and loose material and be supported on piers to the specified undisturbed, B Horizon Sandy CLAY.

The following table shows the bearing capacities for the horizon that may be expected based on the borelogs.

Founding Material Allowable Bearing Capacity (kPa)

B Horizon Sandy Clay 150

4.4. Waffle Raft

A waffle raft footing based upon the AS2870 site classification M, as set out below, is considered suitable for this site. Ensure footings are trenched or piered to firm, undisturbed B Horizon Sandy Clay. (Where bored piers are used they are to be drilled 300mm into the undisturbed natural B horizon Sandy Clay).

The footing system should incorporate piers to allow for foundation settlements caused by the drying effects of Clay soils by tree roots and/or the growth of trees. These piers should be founded a minimum of 2700mm (1.5xHs in accordance with AS2870-2011) or to rock, whichever is shallower. The extent of these piers shall be determined in accordance with Section 5.6.

The footing sizes used, are based upon the recommendations of AS2870 for a site classification of M, and the influence of tree roots in accordance with Section 5.6, when used in conjunction with piers.

It is recommended that where trees and house are to be removed that the soils be rehydrated as set out in Section 5.7 & 5.8 of this report.

These recommendations are a guide only. The footings must be designed by an experienced Engineer familiar with the types of building construction stipulated in AS2870-2011.

The approximate footing sizes expected are:

Waffle pod raft depth (mm) 310

Waffle pod (mm) 225

Slab (mm) 85

Reinforcement 3N16


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Mesh SL82

4.4.1. Site Preparation

1. Scrape vegetation and roots off site.

2. Cut and fill the site to form a level bench, ensure high side of cut is graded well away from

house area so water can freely drain away.

3. Place suitable quarry product, fine crushed rock, over the building area, up to 50mm

nominal depth, as required to form a level platform. Fine crushed rock to be compacted

to a smooth, hard surface. The construction process may be made easier if this material

extends 1.0m outside the building line.

4. Where uncontrolled fill or disturbed soil occurs, edge beams are to be trenched, over

excavated or piered 200mm into the undisturbed, firm natural Sandy Clay horizon. Rolled

fill is not suitable to support the edge beams. Internal ribs are to be piered 200mm into the

undisturbed, firm natural Sandy Clay horizon. (If bored piers are used these are to be drilled

300mm into the firm natural B horizon Sandy CLAY).

Note: (1) Pre-existing site fill is not to be considered rolled fill unless excavated and re- compacted in layers not exceeding 150mm at an appropriate moisture content.

(2) Requirements for easement effects and tree protection zone need to be additionally considered.

5. Set up string lines and formwork edge boards.

6. Lay plumbing lines ensuring that risers are firmly staked. Ensure pipework through beam

penetrations is lagged in accordance with the requirements for the site classification.

7. Lay out an approved 0.2 mm plastic membrane over the building area.

8. Place waffle boxes/pods and reinforcement in accordance with Engineer designed footing

plan and detail sheets.

9. Ensure boxes/pods which are cut around plumbing pipes are taped and sealed.

5. Special notes for construction relevant to this site

5.1. Windspeed Assessment Classification

The site was investigated and found to have the wind rating category classification

• N1 = Vh < 28 m/s

The windspeed calculated, Vh is for use in permissible stress design only. It has been calculated for a domestic construction in accordance with the limitations as in AS4055.

The above wind rating for this site is suitable for single storey construction. If a multi-level building is to be constructed on this site contact FMG Engineering for further advice.

5.2. Flexible Connections

Flexible connections in the stormwater and waste drains should be considered by the Footing Design Engineer.


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5.3. Articulation

For this site, construction joints in brickwork are mandatory.

FMG Engineering can prepare a control joint plan upon request. A fee will be charged for this work.

The footing design has been prepared for an articulated masonry veneer construction. If this is not correct, the footings design will need to be amended for a non or partially articulated building.

The articulation of masonry (as deemed necessary by the Footing Design Engineer) shall be in accordance with Technical Note 61 published by the Cement and Concrete Associations of Australia.

Foundation movement may be a cause of visible cracks in buildings. It is important to provide flexibility of the structure by considering full height openings (doors and windows) or construction joints at suitable spacings.

Note: Building material movements can, and do, also cause minor cracking known as ‘settling in’ movements.

5.4. Site Drainage

The building area is to be graded away from the house so water drains to collection sumps and cannot pond beside or adjacent to the footings. On the cut side, water must drain away along the base of the cut. Provide a spoon drain if necessary. During construction provide temporary stormwater drains.

Care shall be taken with temporary surface drainage of the allotment from the start of construction. The completed drainage system shall be installed as soon as practical after the finish of construction of the house in accordance with Australian Standard “Residential Slabs and Footings

– Construction” AS2870-2011 Clause 5.6.3 (a).

5.5. Sewer/Easement

Where service trenches or easements are close to the footings, the footings are to be supported on piers constructed to sufficient depth that a line drawn at 30 degrees for sandy soils and 45 degrees for clayey soils from the base of the pier/s cuts the service trench line below the base of the service trench.

5.6 Tree Effects on Soil Moisture Conditions

As the site has been classified 'P' due to the presence of trees, our footing recommendation

is based on the current heights of the trees and future mature heights, as shown on the

attached Site Plan. The influence of these trees on the footing design will be considered

according to clause (2) below.

There are also some trees whose roots (at this time) are not likely to be causing abnormal

moisture conditions in the foundation beneath the likely building footprint. However, over

time, the zone of influence of the tree roots may encroach upon the building footprint and

cause soil movement. These trees have been considered in the footing recommendations.

With respect to tree roots possibly creating, or contributing to, abnormal site moisture

conditions, we provide the following advice.


FMG Ref: 271472-S50436

1. Abnormal soil moisture conditions as a result of the intrusion of tree roots beneath the

dwelling footprint including any of its appurtenances such as verandas, paving, decking and

the like, may develop at some time.

2. Should the anticipated mature height (h) of the species when inserted in the empirical

relationships shown below, indicate that the radial zone of tree root influence measured

horizontally from the tree base (distance = d), encroach upon the building footprint then

adequate precautions to protect the footing from the effect of abnormal soil moisture

conditions caused by tree root activity was considered.

d = 1.0h (single tree)

d = 1.5h (group of trees)

d = 2.0h (row of 4 or more trees)

It must be noted that due to matters such as complex tree root geometry, variable moisture

extraction (depending upon tree species) and the difficulty in predicting future growth and

watering patterns, a PRECISE rational design for the effects of trees is outside current

Engineering knowledge. Engineers are not experts in tree growth and cannot be expected

to know the anticipated growth and mature height of trees.

While a design using current knowledge of tree effects has been carried out it must be

accepted that there is a higher probability of damage occurring due to ‘abnormal’ soil

moisture than would be anticipated in this case for a site subjected to only ‘normal moisture

conditions’, as defined in AS2870 - 2011 Section 1.3.

5.7 REMOVAL OF TREES AND REHYDRATION OF SOILS

The building area and environs contain significant trees which may affect the foundations of the proposed building. Where trees are to be removed from the area where they may affect the footing foundation within the trees’ zone of influence. The site shall be re-hydrated before building commences.

The recommended rehabilitation process for tree removal involves the removal of the tree stump and excavating a hole (approximately, 1.5 to 2m diameter) widened by backhoe or similar. The hole is to be completely filled with water and the water allowed to soak in. The water filling should be done three times at intervals of about two days. After this, the hole is to be backfilled with approved granular fill and compacted to a relative density of not less than 95% standard compaction (AS1289, Clause 5.1.1).

5.8 EXISTING STRUCTURE ON SITE

Remove existing footings and building rubble. Fill excavation with non-porous fill compacted in maximum 150 mm layers to 95% standard compaction per AS1289, 5.1.1.

Where an existing house with timber floors is to be removed from the site and a new building with a slab is proposed, pre-wetting is mandatory using the following procedure. Demolish


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existing house but leave strip/stone footings in place. Fill between footing beams with water and allow to soak in. Repeat often, for 14 days minimum. Allow further time for surface to dry sufficiently, to allow work to proceed on site, then demolish and remove the old footings. Fill holes with non porous fill compacted in maximum 150 mm layers to 95% standard compaction per AS1289, Section 5.1.1. Scrape site and remove all remaining rubble and organic matter, then proceed with footing preparation.

In the location from which the previous house has been removed the soil will require ‘wetting up’ if the house had timber floors. Pre-wetting can be carried on using sprinklers or similar to pre-soak the site area for approximately 3 hours daily for 10 days. Allow a minimum of 3 days prior to preparing bench level using approved compacted fill (95% standard) over this area.

5.9 New site investigation required

After existing structures are removed from site a final Site Classification of this site is recommended. Fill and disturbed natural soil may be present after demolition and the new investigation can provide information regarding the approximate depths of fill for costing and design consideration.

6 Potential construction difficulties

6.1 Soft Soils

Due to the nature of soils on this site, the soils may become soft and boggy during wet weather.

Surface fill or natural Sands may cause collapse of side of excavations.

Back hoe piers are recommended.

7 Other important information about this report

7.1 Variations from the Report

FMG Engineering advises that soil borelogs are most often based upon disturbed auger samples or continuous core samples taken down to a depth in one or more positions on the site. It is not possible by this means to detect all sub-surface features which may exist at a particular site. For example, the depth to solid rock may vary greatly over the area of a site. A filled well or cellar may go undetected and naturally occurring anomalies in an otherwise homogeneous soil mass can be easily missed. As such, any variations or discrepancies in soil type, colour, horizon depth, or rocks encountered must be reported to the Footing Design Engineer immediately so that their potential influence on the footings may be assessed. Studies have shown that a large number of boreholes leads to only a slight increase in the probability of detecting hidden site features in foundation soils. The number of boreholes drilled at the site has been carried out in accordance with current standard industry practice. A more detailed site investigation can be carried out, if required. An additional fee will be charged for this work.


FMG Ref: 271472-S50436

7.2 Future Tree Planting/Landscaping

Proposed landscaping and tree planting may affect footing performance. A review of the site classification and footing design is required when information on future planting and landscaping is available.

If, following construction of the house, the Property Owner changes the vegetation on the site (either by planting or removing trees or large shrubs) the Property Owner should seek advice from a Footing Design Engineer on the potential effects of any such changes on the footings system.

A qualified Arborist can check and establish the species of plants and how they may influence the site. FMG Engineering recommends the Property Owner consults an Arborist for such advice.

Reference should be made to CSIRO Sheet 10-91‘Guide to Homeowners on Foundation Maintenance and Footing Performance’ for tree root zone of influence.

7.3 Foundation Maintenance

The appropriate site drainage, paving, and foundation maintenance should be implemented as soon as possible after completion of construction of the building.

A copy of the CSIRO Sheet No. 10-91 ‘Guide to Homeowner or Foundation Maintenance and Footing Performance’ has been included in the Property Owner’s copy of this report.

AS2870 embraces the philosophy that optimum performance of rational and economical footing designs can only be achieved with the cooperation of informed Property Owners who pay attention to maintaining a stable moisture condition of the foundation soils as recommended in the above referenced CSIRO Notes.

7.4 Important Notes to the Owner(s)

This soil report is a very important document and should be kept in a safe place so that you may refer to it in the future. You should hand it on to the next purchaser of this house.

It contains not only design details about the footings for your house but the notes contain important recommendations on how drainage, landscaping and tree planting can affect your home. Refer to the notes when planning your garden.

FMG Engineering warns that it is sometimes not possible (on a statistical basis) to determine any or all sub-surface anomalies which may exist at a particular site by the borehole sampling

technique as currently used and recommended by AS2870 for the limited geotechnical investigation of residential building sites.

Current state-of-the-art investigation procedure involves the sinking of up to three 40mm diameter boreholes, Be advised that one of the limitations of the borehole sampling technique is that it may not in all instances allow an exact interpretation by the soil logger of fill soil depth or the extent of filling soil at a site.

It can sometimes be difficult to assess and identify fill as being different from its boundary with a naturally occurring soil profile particularly in situations where the fill soil is itself derived from the site under test, or from some nearby location exhibiting a similar profile in terms of soil type, colour and texture. This may mean that for some sites it will be necessary for additional foundation costs to be passed on by builders to building owners.

This can best be dealt with by owners requesting builders to show any specified foundation treatment mentioned in this report as a "Provisional Cost" (PC) amount clearly showing what


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the builder has allowed for when quoting foundation treatment works such as pier installation.

FMG Engineering shall not be held responsible for additional costs that may be incurred by builders or owners from time to time that may be caused by or arising out of any foundation treatment works relating to the depth or extent of filling soil that may be discovered after work by the builder commences on site.

The chance of discovering buried anomalies such as old wells, filled cellars, rock outcrops, soil filling and/or any other sub-surface intrusions increases only marginally with an increase in the frequency of sampling.

If a more comprehensive site investigation is desired, PRIOR TO THE COMMENCEMENT OF CONSTRUCTION, then this office should be notified and we will be pleased to act upon your further instructions in this regard.

Any additional site investigation work requested will incur an additional fee which will be negotiated at the time of your issuing such instructions.

Any distinct variations or discrepancies in soil type, colour, texture, composition or horizon depth observed by the client, or any of his servants or agents, must be referred to the Engineer immediately upon discovery. Further advice may be necessary from the Engineer as a result of such discovery. A site visit may be necessary.

In accordance with current state-of-the-art practice, this office uses the push tube or percussion tube method of retrieving soil core samples. These methods have been found to be the most cost-effective means of site investigation currently available.

For notes and details concerning footing and site preparation including earthworks, concrete and steel reinforcement, service trenching, paving requirements, site drainage, retaining walls and articulation of superstructure walls, the owner is advised to read this report and its appendices in their entirety.

8 Provisions

8.1 Property Owner

The Client, or agent of the Property Owner, Builders, Designers, or any person(s) acting on behalf of the Property Owner, must ensure that the Property Owner receives a copy of this report so they are fully informed about their obligations and responsibilities.

TO THE OWNER: This soil report is a very important document and should be kept in a safe place so that you may refer to it in the future. You should hand it on to the next purchaser of this house.

It contains not only design details about the footings for your house but the notes contain important recommendations on how drainage, landscaping and tree planting can affect your home. Refer to the notes when planning your garden.

8.2 Design – Management - Quality

The work carried out in the preparation of this report has been performed in accordance with the requirements of FMG Engineering’s Quality Management System which is certified by BSI Group to comply with the requirements of ISO9001.

8.3 Copyright

The Site Classification Report has been prepared expressly for the Client for the sole purpose of providing a site classification and site information, based on AS2870. This report


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is copyright to FMG Engineering. No part of this report, including the whole of same, shall be used for any other purpose nor by any third party without the prior written consent of FMG Engineering.

FMG Engineering will not accept liability either wholly or in part, for the use of this report by a third party or for any purpose until and unless such permission has been duly granted in writing, as matters not specifically mentioned in the report may have been taken into account in determining footing options.

This report must not be reproduced, except in full and with the written approval of FMG Engineering.

Glenvill Homes Pty Ltd 6 Allie Street, SURREY HILLS, VIC 3127 31/07/2020

FMG Ref: 271472-S50436

Site Photos


FMG Ref: 271472-S50436


FMG Ref: 271472-S50436

7/30/2020 Bore Log v4.2 - NetSuite

https://1048422.extforms.netsuite.com/app/site/hosting/scriptlet.nl?script=221&deploy=2&compid=1048422&h=16e16303d1f1c658bc5b&siteid=42645&qzx=65d1e30c267764ed582da49abf5 1/1

FMG ENGINEERING SURFACE SOIL BORE LOG

Job: S50436/271472 Site: 6 Allie Street

Job Date: 27/7/2020 SURREY HILLS VIC 3127

Sample Method: Hand Auger

HorizonHole 1Depth(mm)

Hole 2Depth(mm)

Hole 3Depth(mm)

Description USCS Moisture Strength Est Ips %

FILL 0 - 300

0 - 400

0 - 600

(FILL) CLAYEY SILT SAND, mix w/ gravels, brown - grey, moist poorly compacted LowPlasticity.

Moist 1.0

A 300 - 600

400 - 800

CLAYEY SILT SAND, brown - grey - yellow, moist moderate density perched water atbase (BH02 only) Low Plasticity.

SM Moist Medium 1.0

B 600 - 1100

800 - 1600

SANDY CLAY, orange - yellow - grey, moist stiff, grading into clayey sand. Refusal onsands/dense clayey sands Medium Plasticity.

CI-CH Moist Medium to High 3.0

Ys 22 19 11 Ys = Characteristic surface movement (mm)

Yt 32 32 11 Yt = Potential surface movement due to tree induced suction change (mm)

Ground water not encountered at the time of drillingSurface Suction Change: 1.2 pF

Depth of design soil suction change (Hs): 1.8 m

Tree: Group of Trees

Tree Distance (Dt): 5.0 m

Design Height of Tree (HT): 10.0 m

0.9 tree factor has not been appliedMax Design Drying Depth (Ht): 3.3 m

Influence distance (Di): 1.5xHT

Calculation in accordance with AS 2870 - 2011

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