1. Topic 7: Timber Subfloor Systems – Basic
Unitec New Zealand
Construction Systems 1
Topic introduction, overview and threshold concepts.
Remember this is a big lecture keep it moving
Topic 7: Timber Subfloor Systems – Basic
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2. Intention of this short overview.
Students will be introduced to the fundamentals and basics of the topic area content.
Typical elements used in Timber sub floors will be identified using photos , images and drawings .
Words and terms used to describe and identify elements will be explained .
Terms used in the design of the major elements such as Spans and Loaded Dimensions will be introduced leading to future detailed discussion in breakouts.
Design approaches to simple layouts will be outlined with terminology defined and explained for future discussion in tutorial breakouts.
Additional non structural functional requirements of sub floor framing identified , implications and prevention of possible problems.
Additional requirements and terms that relate to residential timber mid floor framing

3. Timber Subfloor
Definition: Subfloor refers to the bottom-most structural floor underneath the decorative or "finished" floor.
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
Sub floor elements shown in context with concrete slab and foundation walls which often provide some form of support.
© Unitec New Zealand

4. Timber Subfloor
It is also referred to as a suspended timber floor system as the floor is built up off the ground creating a ventilated space in between.
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
© Unitec New Zealand

5. Timber Subfloor – typical sequence of construction
Typical sequence of construction. Usually a concrete slab on ground will have been laid already. These elements will be the focus of lecture topic 10 in week 4 .
Every building needs a site .
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
Excavations carried out and then strip footings and foundations walls for concrete slab provided.

6. Timber Subfloor – typical sequence of construction
Elements of concrete slab in place. This building also had some masonry piers
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
Concrete and masonry elements in context with the site.

7. Timber Subfloor – typical sequence of construction
Circular concrete footings poured to required depth of embedment
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
Footings in the ground.

8. Timber Subfloor – typical sequence of construction
Treated timber piles are embedded in the footings.
Treated timber bearers then span between the supporting piles.
Direction, layout and sizes will be decided by the designer using NZS
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
The distance between bearer supports is called the BEARER SPAN.
This is the same as the PILE SPACING.

9. Timber Subfloor – typical sequence of construction
The sub floor joists will span onto the bearers but sometimes onto other elements such as stringers and plates , eg where masonry piers are present.
Treated timber joists span onto the bearers and sometimes onto elements called Stringers.
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
Stringers are usually fixed to slab edges or walls.
Joists can also span onto timber plates on a DPC over masonry piers .

10. Timber Subfloor – typical sequence of construction
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
Finished assembly of elements of a residential timber sub floor framing proposal .
Yellow piles are where designer identified the need for extra piles to deal with special loads from above.

11. Timber Subfloor – typical sequence of construction
Finished sub floor framing in overall house context shown on right and includes later framing for decks.
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
Design of framing for decks follows practically the same design procedure but installation at later construction stage.

12. Timber Subfloor – What is a LOAD ?
A structural load is basically weight or MASS but it takes into account the effects of gravity
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
MASS is measured in Kgs but LOADS are usually calculated using a unit called the Newton. Don’t worry , structural engineers usually get paid to do all the hard calculations

13. Timber Subfloor – What is a LOAD ?
Unit of mass is a KG
A LOAD is a FORCE The unit of both is the NEWTON
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
NZS 3604 has tried to make things easier for designers . They employ a method called the LOADED DIMENSION.

14. Timber Subfloor – What is a LOADED DIMENSION ?
When starting to study NZS 3604 it may help to think of the span distances and measurements as being similar to, or as representing weights and forces.
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
If each man represents a metre ( 1m ) , what are the loaded dimensions of the men on the bottom row ? 1. 2. 3.

15. Timber Subfloor – What is a LOADED DIMENSION ?1. 2. 3.
Doing this takes practice and so does trying to identify the loaded dimension so don’t be too worried if you don’t get it first time .
Hang in there , look at NZS 3604 and ask your tutor to go over the things you are not sure of .
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)

16. Timber Subfloor – What is meant by SPAN?
Structurally- effective span is “ The centre to centre distance between the supports of a beam, girder , or other structural member.
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
Akashi Kaikyō Bridge- Longest main central span since Span is 1991 metres

17. Timber Subfloor – What is meant by SPAN?
Lets get back to basics or at least the residential scale
Diagrams from NZS 3604:2011
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
If you can’t quite understand whats happening in the sub- floor structure try sketching it out and add notes .
Ask if still not sure what’s happening.

18. Timber Subfloor – What is a CANTILEVER?
Member 3 at right is a CANTILEVER.
The support of the element above is at one end only.
A CANTILEVER is fixed or supported at one end.
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
Its basically a diving board !!!

19. END “ Next session we will be studying Mid Floor systems “
“May the Loaded Dimension be with you “
END
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