Allied READY SUPERslab
Design and Installation Guide
Consult your Allied Concrete
representative for specialised information.
0800 4 ALLIED
0800 4 225 433
www.alliedconcrete.co.nz
ALLLIED READY SUPER SLAB – DESIGN AND INSTALLATION MANUAL
Revision History
Revision
Prepared by
Description
Date
A
RJF
Draft
20 March 2013
B
AE
Draft
17 April 2013
DISCLAIMER
This document has been prepared solely for ALLIED CONCRETE. The use of and reliance upon the information
or opinions contained in this document by others without prior written consent from HFC Foundations Limited
will be at such person’s risk. HFC Foundations Limited accepts no responsibility or liability for the consequences
of the unauthorized use of this document.
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ALLLIED READY SUPER SLAB – DESIGN AND INSTALLATION MANUAL
CONTENTS
1.0
GENERAL .......................................................................................................................... 3
2.0
ALLIED SUPER SLAB COMPONENTS ...................................................................................... 4
2.1
Polystyrene Pods............................................................................................................. 4
2.2
Topping slab and rib reinforcement [FIGURE 4.1] ............................................................... 4
2.3
Concrete ........................................................................................................................ 5
3.0
STANDARD DESIGNS AND LIMITATIONS ............................................................................... 6
3.1
Structures Supported by the standard Allied Super Slab ...................................................... 6
3.2
Ground conditions ........................................................................................................... 7
3.3
Lateral resistance ............................................................................................................ 7
4.0
STANDARD DETAILS: NEW ZEALAND .................................................................................... 8
5.0
SPECIAL DETAILS: CANTERBURY REGION............................................................................... 9
6.0
INSTALLATION INFORMATION ............................................................................................10
6.1
Site preparation ............................................................................................................10
6.2
Set out & boxing............................................................................................................11
6.3
Damp proof membrane (DPM) .........................................................................................12
6.4
Pod set out ....................................................................................................................12
6.5
Perimeter foundations .....................................................................................................13
6.6
Internal ribs ...................................................................................................................14
6.7
Mesh ............................................................................................................................14
6.8
Reentrant corners ...........................................................................................................14
6.9
Concrete placing, finishing and curing. ..............................................................................15
6.10
Saw cutting and control joints. ..........................................................................................16
7.0
LANDSCAPING AND ONGOING MAINTENANCE ..................................................................17
7.1
Paving and landscaping heights .......................................................................................17
7.2
Excavation and retaining walls ........................................................................................17
7.3
Drainage of the site .......................................................................................................17
7.4
Gardens, trees and shrubs...............................................................................................18
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ALLLIED READY SUPER SLAB – DESIGN AND INSTALLATION MANUAL
1.0
GENERAL
This document details the design and construction requirements for the Allied Super Slab system.
The document covers the components, general site requirements, details and construction of a standard
Allied Super Slab. In addition more specific special details are provided for guidance only.
This document does not replace the requirement for specific engineering design and documentation by a
professional engineer as part of the consent process.
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ALLLIED READY SUPER SLAB – DESIGN AND INSTALLATION MANUAL
2.0
ALLIED SUPER SLAB COMPONENTS
The Allied Super Slab floor system consists of polystyrene void formers separated by 100mm wide
spacers set out in a grid pattern. Concrete is poured on top of the pods and within the 100mm wide gap
between the pods to form a ‘waffle raft’.
A standard design consists of 85mm topping over a 200mm pod creating an overall slab thickness of
285mm.
2.1
Polystyrene Pods
Polysytrene pods are typically 1100mm x 1100mm in plan and 200mm thick.
Depending on supply in some cases 1200mm x1200mm x 200mm pods are used.
Pod thickness is increased in some cases and in the Canterbury Region 300mm pods are used as standard
to comply with the requirements of the Department of Building and Housing for TC2 sites.
Where topsoil thickness is such that imported hardfill is required to bring the slab up to level then the
thicker 300mm pod and resulting 385mm thick floor system can be used to reduce the thickness of hardfill
required.
Once a level platform has been created with a combination of compacted hardfill, a blinding layer and a
layer of damp proof membrane (DPM) then the pods can be set out in a grid pattern to create 100mm
wide ribs.
Where the geometry of the slab dictates the pods need to be cut to ensure the 100mm wide rib spacing is
maintained and perimeter footing widths are correct.
2.2
Topping slab and rib reinforcement
[FIGURE 4.1]
The thickness of concrete over the polystyrene pods is typically 85mm.
Reinforcement within the topping is either 665 mesh for areas of low seismicity or SE62 ductlile mesh in
areas with high seismicity. It is recommended that the ductile SE62 mesh is used.
Thicker toppings and a variety of mesh sizes are also used to accommodate under floor heating or higher
superimposed design loads in some cases.
The reinforcement in the bottom of the 100mm wide ribs is a single HD12 E bar and these run in two
orthogonal directions following the rib lines.
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ALLLIED READY SUPER SLAB – DESIGN AND INSTALLATION MANUAL
Perimeter reinforcement typically consists of 2 HD12 E bottom bars as well has HD12 E starters bars
lapping with the top mesh reinforcement.
Bar chairs and spacers are used to ensure the correct cover to reinforcement as well as ensuring the mesh is
lifted off the pods to provide the correct top cover.
Additional reinforcement is provided for specific design cases such as to accommodate higher loads,
spanning between piles or highly expansive soils.
All reinforcement shall be deformed bar to AS/NZS4671:2001. Stirrups, links and binding shall be plain bar
of the above grade or wire to AS/NZS4671:2001.
Welded mesh shall be to AS/NZS4671:2001.
2.3
Concrete
Allied Super Slab Mix should be used for all Allied Super Slabs.
For sites located away from corrosive environments 20 Mpa concrete strength is required. For sites in more
corrosive environment (such as sea spray zones) or for additional strength 25 Mpa concrete is used
Mix code 252RSS is used for 25 Mpa applications.
Mix code 202RSS is used for 20 Mpa applications
The design documentation will specify the required mix code for each design.
Where good access exists around the site and sufficient labour is employed then the concrete can be
placed directly from the truck using the chute or wheel barrows. If this is the case then it is important that
the mesh reinforcement and pods are protected from wheel barrow traffic and correct covers are
maintained.
Alternatively a slump pump can be used with either 13mm or 19mm aggregate.
At the time of ordering it is important to state the method of concrete delivery so that any adjustments in
concrete mix can be made by Allied Concrete
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ALLLIED READY SUPER SLAB – DESIGN AND INSTALLATION MANUAL
3.0
STANDARD DESIGNS AND LIMITATIONS
The standard Allied Super Slab is an extremely strong and durable foundation system and can
accommodate a wide variety of loading combinations.
The following sections outline the general loading requirements for a standard Allied Super Slab.
Specific designs for more onerous design cases can be carried out for any project and they normally only
require a minor variation to the standard design. All designs are carried out by a Chartered Engineer
with specific plans and details provided at consent stage.
3.1
Structures Supported by the standard Allied Super Slab
The standard Allied Super Slab is designed to support lightweight timber framed houses generally
satisfying the requirements of NZS3604:2011. Solid masonry construction is excluded from the standard
design but can be accommodated by specific designs in most cases.
The criteria for complying with NZS3604:2011 include but are not limited to:












Building founded on ‘good ground’
Importance level 1 and 2 structures
Total height to the highest point of the roof up to 10m
Open ground snow loading up to 1kPa
Buildings with floors not exceeding 3kPa uniformly distributed or 2.7kN concentrated loads
excluding garages
Garage loading up to 2.5 kPa uniformly distributed or 13 kN concentrated loads for vehicles up
to 2500 kg tare.
Exterior cladding to be either lightweight or masonry veneer up to 220 kg/m2 with a maximum
height of 7m above finished ground level.
Masonry construction is excluded from the standard design case but can be accommodated
through specific design
Timber framed upper level floors up to 3 levels
The slope of any roof plane shall not be steeper than 60 degrees.
From low to Very High wind zones
A maximum heavy veneer height of 5.5m on gable ends
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ALLLIED READY SUPER SLAB – DESIGN AND INSTALLATION MANUAL
3.2
Ground conditions
The standard Allied Super Slab can be used on ‘good ground’ in accordance with NZS3604:2011 section
3.1.3 which includes (but is not limited to) a geotechnical ultimate bearing capacity of 300 kPa (equivalent
to 100kPa allowable bearing).
In addition to good ground sites the standard slab can be specifically designed to accommodate the
following (subject to site specific geotechnical information)








3.3
Low bearing sites down to a geotechnical ultimate bearing capacity of 150 kPa (equivalent to 50
kPa allowable bearing)
Floating slabs on gravel rafts over peat site
Fully suspended piled slabs
[refer figure 4.6]
Moderately, Highly and Extremely expansive sites
Bridging over public services
[refer figure 4.5]
Slope stability piles
Basement retaining walls
Canterbury region TC1, TC2, TC3 sites
[refer figures 5.1 to 5.4]
Lateral resistance
Lateral resistance to sliding from seismic actions is generally resisted by friction between the slab and the
underlying ground surface.
In areas of high seismicity additional resistance to sliding is provided by the use of shear keys. Shear keys
consist of drilled piles of 900mm depth spread around the perimeter of the slab to lock the slab into the
ground. Where shear keys are required they will me indicated on the drawings provided.
[refer figure 4.2]
In some circumstances shear keys are not adopted even in high seismic areas (such as the Canterbury
Region).
Where shear keys are not adopted in high seismic zones additional measures need to be taken to protect
services which run through the slab from being damaged under a serviceability earthquake event.
Pipe work can be run within the depth of the slab and exit out of the side of the footing with a flexible
junction. This method mitigates the likely hood of damage as well as providing an accessible point to
repair services should they be damaged.
[refer figure 5.3]
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ALLLIED READY SUPER SLAB – DESIGN AND INSTALLATION MANUAL
4.0
STANDARD DETAILS:
NEW ZEALAND
FIGURE
TITLE
4.1
4.2
4.3
4.4
4.5
4.6
Standard slab details
Typical shear key
Typical step detail
Typical block retaining wall detail
Typical bridging detail for public lines
Typical fully suspended slab detail
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ALLLIED READY SUPER SLAB – DESIGN AND INSTALLATION MANUAL
5.0
SPECIAL DETAILS: CANTERBURY REGION
FIGURE
TITLE
5.1
5.2
5.3
5.4
Typical edge beam TC2 & TC3 sites
Typical internal stiffening beam TC2 & TC3 sites
Typical service penetrations TC2 & TC3 sites
Re-level able Jacking slab TC3 sites
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ALLLIED READY SUPER SLAB – DESIGN AND INSTALLATION MANUAL
6.0
INSTALLATION INFORMATION
The following section outlines the standard installation details for the Allied Super Slab. For specific
projects non-standard details may be required and the builder should construct these in accordance with
the drawings, the NZ Building Code and good practice.
All construction should be inspected by an engineer, the council and/or an approved representative of
Allied Concrete who has been specifically trained.
All bending of bars should be carried out in accordance with NZS3101:Part 1:2006. Minimum bend
diameters for main reinforcing bars (between 6-20mm dia.) bar should be 5 x diameter of the bar (db)
measured to the inside face of the bend.
All bar laps should be 50 x db or greater
6.1
Site preparation
The site should be cut to underside of slab level plus any extra allowance for hard fill and blinding layers.
All topsoil and organic matter should be removed from under the entire slab area and any soft spots
should be excavated and replaced with compacted material to achieve the site specific ground bearing
requirements (normally 100 kPa allowable)
The cut platform should not be left exposed to dry out for any length of time particularly in areas where
expansive soils have been identified. If necessary on dry cut platforms the site should be thoroughly
wetted prior to the placement of hard fill or fines. Failure to do so can result in excessive ground
movement and damage to the slab particularly on highly and extremely expansive sites.
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ALLLIED READY SUPER SLAB – DESIGN AND INSTALLATION MANUAL
Granular fill complying with NZS3604:2011 clause 7.5.3 shall be placed and compacted in layers of
150mm maximum thickness up to a maximum thickness of 600mm (or thicker under the supervision of a
geotechnical engineer)
A sand blinding layer of 15mm should be used over the platform to protect the DPM from being punctured
by the aggregate within the hard fill.
The cut platform and any compacted hard fill should be inspected and approved prior to continuing on
with construction.
6.2
Set out & boxing
Site profiles, levels and position on site should be determined by the builder and/or surveyor
Boxing of correct height and levels should be erected around the perimeter of the slab ensuring that any
boxing supports do not penetrate the DPM layer.
Rebates for brickwork, garage door thresholds and joinery should be allowed for in the boxing.
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6.3
Damp proof membrane (DPM)
A continuous damp proof membrane should be placed on top of the sand blinding layer over the entire
slab area in accordance with NZS3604:2011.
Where polyethylene (polythene) sheet damp proof membrane is to be used the material should be not less
than 0.25mm thick , have lapped joints not less than 150mm wide which are sealed with pressure sensitive
plastic tape not less than 50mm wide. The DPM should be protected from damage during construction.
6.4
Pod set out
The polystyrene pods should be placed on the DMP layer within the perimeter boxing as per the set out
drawings provided.
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The set out of the pods should ensure that the perimeter footing width (normally 300mm wide) is correct
and the space between pods is correct (normally 100mm). The drawings and details should be carefully
checked as in some cases footing and rib widths are varied to suit site specific requirements.
Internal load bearing walls will be marked on the drawings and these also need to be accommodated in
the pod set out (or cut into the pods if preferred).
Where pods require cutting to suit the dimensions and set out of the floor care should be taken to ensure
that the remaining pods are no less than 200mm wide. Where narrow < 200mm pod widths occur then
the pod should be removed OR the set out merged with an adjacent full width pod to create two
narrower pods of 600-800mm wide with a standard 100mm wide rib between.
The maximum pod size in all cases should not exceed 1200mm
6.5
Perimeter foundations
The perimeter edge beam is typically 300mm wide however
larger widths are specified when ground conditions or edge
detailing of cladding dictate this.
Typically 2 HD12 bars (Grade 500E deformed bars) are
used for bottom steel in the footing and 1 HD12 used as top
reinforcement where required. The bottom bars should be
placed onto bar chairs to achieve 50mm bottom and side
cover.
HD12 starter bars are used of varying lengths depending on
site conditions and levels of soil expansiveness, and these
should be tied to the mesh.
The perimeter footing may have rebates to accommodate
exterior cladding details such as bricks, garage door
rebates, and full height joinery rebates. The rebates should
be coordinated and set out in accordance with the architects
drawings.
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6.6
Internal ribs
A standard internal rib is 100mm wide and has 1 HD12 bar
located in the bottom of the rib with 50mm cover to the DPM.
Extra wide ribs or ribs with additional reinforcement including
links can be specified to suit site specific requirements.
Ribs should run from one side of the slab to another in a straight
line where possible. HD12 bars should be lapped 600mm
where required.
6.7
Mesh
The typical mesh used in the 85mm topping is SE62 grade 500 E mesh.
The mesh should be supported on 40mm chairs for an 85mm topping. The chairs should be located on top
of the polystyrene pods and be of sufficient number to ensure the mesh does not sag excessively between
support points.
Where the topping is increased above 85mm the mesh size may be increased and the chair size may also
need to be increased to achieve 40mm top cover.
6.8
Reentrant corners
At re-entrant (internal) corners additional steel is required to prevent cracks from propagating from the
internal corner into the slab. The additional steel will be indicated on the drawings and consist of 2 HD12
bars, 1500mm long placed diagonally across the corners.
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6.9
Concrete placing, finishing and curing.
PLACING:
Only Allied Mix code 252RSS should be used for 25 Mpa applications or Mix code 202RSS used for 20
Mpa applications unless specifically varied by the designer or concrete supplier. Failure to use the correct
Allied concrete specified may prevent the contractor from obtaining Code of Compliance.
Concrete placing should be carried out by experienced contractors and should be carried out strictly in
accordance with NZS3109:1997
No water should be added to the as delivered concrete unless approved by the design engineer within the
restrictions of NZS3104 clause 2.9.3.1
Concrete should not be placed until all reinforcement has been inspected by the engineer, council and/or
an approved engineers representative. Failure to carry out a pre-pour inspection may result in difficulties
in obtaining code of compliance.
Care should be taken during the pouring process to ensure that the polystyrene pods do not move around.
Ideally concrete should be placed on top of each pod prior to infilling between the ribs to prevent pod
floatation or movement during concrete placing.
The concrete shall be placed so that its working face is generally vertical, and normal to the direction of
placing. It should be placed over the width of the slab in such a manner as to minimize segregation.
Concrete should be thoroughly vibrated around all steel and against all boxing and formed rebates within
the perimeter of the slab.
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ALLLIED READY SUPER SLAB – DESIGN AND INSTALLATION MANUAL
FINISHING
The top surface of the slab should be screeded immediately after placing/vibration has been completed.
Screeding should be carried out with a level as a reference to ensure the top surface is finished within
tolerance.
A trowel and an edging tool should be used to finish the slab to a U3 finish in accordance with
NZS3114:1987. The finish surface should be blemish free with all slab edges tooled off to form a
rounded edge to prevent cracking.
CURING
When the possibility of heat, wind, rain or low humidity could induce premature drying of the top surface
the contractor should either delay the pour or take appropriate actions to mitigate plastic cracking forming
in the surface of the slab.
Where a risk of plastic shrinkage cracking is present the concrete placer shall apply an anti-evaporation
agent over the concrete surface after screeding to prevent excessive evaporation of water from the
concrete surface.
Additional curing measures including ponding of water on the surface of the slab, sprinkling the slab
surface regularly or the use of wet sacking placed over the slab can also be adopted.
Where a large change in ambient temperature is expected during the first 24 hours such as a very cold
night then continuous wet curing via ponding or sprinkling is recommended to mitigate thermal shock and
cracking in the slab.
6.10
Saw cutting and control joints.
Saw cut joints should be cut into the slab within the 24 hours after pouring once the slab is sufficiently hard.
Early entry soft cutting is recommended.
Saw cuts should be 25mm deep (for the standard 85mm topping). For thicker toppings deeper saw cuts
will be required of approximately 1/3rd of the topping thickness. Saw cuts should be made where
indicated on the drawings.
For larger slabs, formed control joints are required and they will be indicated on the drawings. It is
important that formed control joints are installed where indicated to prevent excessive cracking of long or
irregular shaped slabs.
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7.0
LANDSCAPING AND ONGOING MAINTENANCE
Foundation maintenance should be broadly in accordance with AS280:2011: Appendix B. Particular care
should be taken on sites which are Moderately, Highly or Extremely expansive as work and planting
around the slab perimeter can have a detrimental effect on the slabs performance.
7.1
Paving and landscaping heights
The level of permanent paved, concreted and landscaped surfaces should be kept within the limits stated
in NZS3604:2011 clause 7.5.
For paved or concreted surfaces the minimum step from the internal finished floor level to the finished
exterior level should be no less than 150mm
For grassed or permeable surfaces the minimum step from the internal finished floor level to the ground
level should be no less than 225mm
7.2
Excavation and retaining walls
Excavation next to the edge of the Allied Super Slab should be avoided where possible. Under no
circumstances should excavation take place which will undermine the edge of the slab
Excavation or construction of retaining walls (lower than the slab level) within a 1:4 gradient from the
underside of the slab to the base of the excavation/wall should be avoided. A qualified engineer should
design all retaining walls within this zone to ensure that loss of vertical and lateral support (during
construction or permanently) does not occur.
7.3
Drainage of the site
Sands, silts and clays should be protected from becoming extremely wet by adequate attention to site
drainage and prompt repair of plumbing leaks.
The site should be graded or drained so that water cannot pond against or near the building. The ground
immediately adjacent to the building should be graded to a uniform fall of 50mm minimum away from the
building over the first metre. The site drainage should be maintained for the design life of the building
(normally 50 years)
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7.4
Gardens, trees and shrubs
The development of the gardens should not interfere with the site drainage requirements. Garden beds
immediately adjacent to the slab edge or undermining the slab edge in anyway are not permitted.
Planting of trees should be avoided near the foundations as they can cause damage due to drying of clay
and result in excessive seasonal ground movement.
To reduce, but not eliminate, the possibility of foundation damage, tree planning should be restricted to a
distance from the house as follows
(1) 1 ½ x mature tree height for extremely expansive sites
(2) 1 x mature tree height for highly expansive sites
(3) ¾ x mature tree height for moderately expansive sites
Where rows or groups of trees are involved the above distances should be increased. Please note that
removal of mature trees from the site can also cause issues with ground movement
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