1. Topic 11: Timber Subfloor - Advanced
CONSTRUCTION SYSTEMS 1.
Topic 11: Timber Subfloor - Advanced

2. Learning outcomes
Students will be able to demonstrate their knowledge of this topic by:
Understanding the construction of timber foundations and sub-floor framing and applying the requirements of NZS 3604:2011
Explaining common terminology such as piles, footings, bearers, joists, boundary joists, trimming joists, curtailed joists
Describing acceptable fixing methods for structural elements in a foundation/sub-floor
Identifying the requirements for floor insulation, sub-floor ventilation and sub-floor cladding
Describing the requirements of lateral bracing
Unit Standard 9671:
Element 2: Determine and describe the foundations and sub-structure
>>DEPARTMENT TITLE EDIT IN HEADER & FOOTER

3. Subfloor - Advanced INTRODUCTION
Lecture 6 covered the basic principles of suspended timber subfloors
This lecture covers more advanced aspects and principles
Complexity comes from design and other factors such as varying heights above ground or added requirements such as bracing
So this week we slow down a little and go over what we covered last week, but looking a little closer at some of the finer details and other products.

4. Subfloor - Advanced
Suspended timber floors are made up of the common elements as shown below, but there may be substitutions of different elements to suit specific situations, provide more efficient solutions and achieve greater cost effectiveness.
Good time to review what we learned last week. Pull up 3-D model and wow the class.
“I expect a model like this for POE 5…just joking”
© Unitec New Zealand

5. Subfloor - Advanced Floor Joists
Typically (as sized in NZS 3604:2011) floor joists are solid structural timber members 45mm in width and of a depth (height) varying with the span requirement or joist spacing.
The distance joists are set apart (joist spacing) is determined by the spanning ability of the flooring product. Most can only span 450mm max.  
Ok we looked at floor joists last week.
3604 covers conventional floor joists , 45mm wide and varying depths, 90, 140, 190, 240 & 240
How do we know if a product is acceptable to use in NZ?

6. Subfloor - Advanced Floor Joists
When attempting to span floor joists across distances greater than allowed by NZS3604, consider using an engineered product.
 Other factors:
Span large spaces with limited floor depth
Stiffer floor
Run large diameter services in floor space.
Ok we looked at floor joists last week.
3604 covers conventional floor joists , 45mm wide and varying depths, 90, 140, 190, 240 & 240
How do we know if a product is acceptable top use in NZ?

7. Subfloor - Advanced
Extensive range of alternative floor joist systems available
All come under the heading of engineered wood products
Sell as proprietary systems
Hyjoist
LVL
Posi-strut
Twinaplate etc
There are many different engineered timber products on the market
Joists, Beams, Studs, Rafters
Can build an entire building using eng. timber today
Weyerhauser is engineering a 6-7 storey low rise apartment building
Play Video
List pro’s and cons (ask from video):
Pro’s Con’s
Longer spans Slightly more $ expensive
Uses the whole tree Vibration (extrememly rigid)
No warping, shrinking, nail pops etc..
Silent floor is possible
Large holes for running services
Tall walls (studs)
© Unitec New Zealand

8. Subfloor - Advanced
Alternative Floor Joists
© Unitec New Zealand

9. Subfloor - Advanced Conventional Joist HyJOIST 240x45 spans – 4.4m
Compare spans between a 45 x 240 and a HJ240 90
HyJOIST
240mm Dp. HyJOIST spans – 5.2m single span &
6.1m continuous span
© Unitec New Zealand

10. Subfloor - Advanced Floor Joist Under Walls Load-bearing Walls
Double joists are required
Where there loadbearing wall runs at right angles to the line of the joists, the wall must be located not more than 200m centre-to-centre from a bearer or sub-floor loadbearing wall.
© Unitec New Zealand

11. Subfloor - Advanced
Refer to NZS 3604:2011 Figure 6.1 for the use of a bearer and pile below a loadbearing or braced wall.
A bearer or pile must be within 200mm in these situations.
Delving into a review section here: bear with me
Bearers,
Bearer must be within 200mm of a supported L.B. wall
© Unitec New Zealand

12. Subfloor - Advanced Floor Joist Under Walls
Subfloor support to loadbearing wall parallel to joists
© Unitec New Zealand

13. Subfloor - Advanced Floor Joist Under Walls
Subfloor support to loadbearing walls at right angles to joist
© Unitec New Zealand

14. Subfloor - Advanced Floor Joist Under Walls Non load-bearing Walls
If walls contain bracing and run parallel to floor joists
Either:
Over a joist Or
Supported by 100 x 50 solid blocking
Solid blocking is required at:
Either end of the wall above
Each side of door openings
Max 1.2m crs
Floor Joist Under Walls
© Unitec New Zealand

15. Subfloor - Advanced Bearers
Lecture 6 dealt with describing and designing the layout and use of bearers for simple situations where the bearers are set out in rows parallel to one particular side of the building.
Pretty much dealt with boxes so far, but…..
© Unitec New Zealand

16. Subfloor - Advanced
However, buildings often have more complex plan shapes.
Layout of bearers may also be influenced by other factors:
Location of an internal load-bearing wall
Internal point loads (such as a load-bearing post)
Not always the case in the real world.
Draw on the board how to deal with it
© Unitec New Zealand

17. Subfloor - Advanced Stringers
Horizontal members fixed to the side of a wall or to the side of a timber sub-floor (such as a bearer or floor joist) to support the ends of joists or rafters.
Self-explanatary
© Unitec New Zealand

18. Subfloor - Advanced
Stringer Table 6.5 in NZS 3604:2011 also gives the provision for the fixing of the stringer. Fixings need to be also stated when a stringer is sized.
The fixings are M12 bolts set not less than 100mm into concrete or completely through a timber element.
Two sizes: 190 x 45 or 140 x 45. not a bad ides to pu in a two ply anyway, need 38mm bearing for joists
© Unitec New Zealand

19. Subfloor - Advanced
Stringers for deck attaching details from NZBC E2/AS1 document shows fixings to timber bearers through the cladding.
Refer also to BRANZ House Building Guide for useful detail diagrams.
This is the approved detail, although the 3604 detail is structurally adequate does not comply with E2.
Note EPDM washer (ethylene propylene diene monomer)
© Unitec New Zealand

20. Subfloor - Advanced Pile or Isolated Foundations Min height – 150mm
Ordinary Piles with Anchor piles – 600mm
Braced Piles – 1.5m Conc. / 3.0m timber
Jack Studs (see table will require bracing)
Cantilevered – 1.2
Piles support the bearer above and are set in poured concrete footings.
Tops of piles may be at different heights.
NZS 3604:2011 imposes limitations on maximum and minimum pile heights under

21. Subfloor - Advanced
The different loads imposed on the different bearer lines does mean that the piles supporting a bearer may be at different spacings or the bearer size might vary from row to row.
This needs to be considered as it may be considerably easier for the builder if all the pile spacings and bearer sizes are kept the same using the worst case scenario.
Can vary bearer and joist size to suit, but it’s best to K.I.S.S. carpernters don’t like pulling out nails. I know I’ve pulled out and throuwn away way too much timber in my time.
Which of the bearers on the right takes the biggest load and why ??
Which of the bearers on the right takes the biggest load and why ??
© Unitec New Zealand

22. Subfloor - Advanced Pile footings
Except for driven timber piles, each pile shall be provided with a concrete footing.
Sizing of such footings has 2 elements to consider, pile embedment (depth into the ground), and pile plan size.
NZS3604: 2011 sets minimum pile depths, but these are typically superseded when the soil conditions dictate greater depth is needed eg. With Aucklands expansive clays, the footing depth is considerably more than the minimum in the code.
Review Slide
Basically referring to spacing, height out of ground and fixing. If > 600mm out of the ground need braces.
© Unitec New Zealand

23. Subfloor - Advanced Pile Embedment
Leave a min. 100 mm of conc. below bottom of pile
Pile shall be embedded in its footing sufficiently, or temporarily braced, to provide stability during construction.
© Unitec New Zealand

24. Subfloor - Advanced Footing Depths
Bottom of pile footing should be at least the depth of footing but not less than 200 mm.
Different pile type requirements:
Ordinary piles: 200 mm
Braced piles: 450 mm
Anchor piles: 900 mm
© Unitec New Zealand
© Unitec New Zealand

25. Subfloor - Advanced Footing Plan Size
NZS 3604:2011 footing depth requirement is a minimum only
The altered footing depths described above do not alter the use of the footing sizing table for the plan size of the footing.
If the soil does not provide “good ground” for bearing, then the footing plan size will require to be calculated by an engineer.
Typically, in Auckland’s expansive clays’, the NZS 3604:2011 are acceptable for plan footing sizing, but not minimum depth.
© Unitec New Zealand

26. Subfloor - Advanced PILE TYPES
Piles are vertical members, generally made of timber, that support bearers and transfer loads into the footings.
They come in a variety of different types depending on what function they perform and the distance between the bearer and the ground.
The most cost effective and common is the ordinary pile. It is used wherever possible and supports vertical loads only.
However, suspended timber subfloors are also subjected to potential horizontal loading from wind and earthquake, making it necessary to also use pile systems that can withstand these loads.
The type of system selected depends on a variety of conditions such as the distance between ground and bearer (pile length), soil conditions, cost effectiveness etc. See the following slides.
Review Slide
© Unitec New Zealand

27. Subfloor - Advanced Ordinary Piles
Most common type of pile used everywhere except where a pile needs to be braced. Determining what piles need to be braced and by what system, is calculated separately as part of subfloor bracing, then applied to the pile layout.
Min. 125mm sq. or 140mm diam.
Review Slide
© Unitec New Zealand

28. Subfloor - Advanced
Which one of these is NZS 3604?
What don’t’ we see in the left picture that ensures it complies with 3604 (support to hold up the pile, also is that factory cut down?)
Standard square timber pile foundations awaiting concrete
Reinforced concrete pile foundations awaiting concrete

29. Subfloor - Advanced Anchor Piles
Anchor piles provide resistance to uplift and horizontal loads and the number and location as determined by bracing calculation
Min. 900mm min. deep
Evenly spaced throughout foundation
350mm sq. or 400mm diam. min.
600mm max. height
Fixed w/ M12 bolt or 6kN fixing
Anchor Piles provide lateral stability to the foundation for low lying sublfloors
They resist sideways movement from wind and earthquake and uplift (smaller buildings especially)
Must be evenly spaced, starting with the corners
Larger and deeper in size, 400mm dia. (350 sq.) x 900mm dp.
Fixed with M12 bolt (6 kN)
© Unitec New Zealand

30. Subfloor - Advanced Braced Piles Connect at top end to either
pile, bearer or floor joist
(see diagrams in NZS 3604:2011)
Generally used where clearance is greater than 600mm between ground and bearer
Refer NZS 3604 for pile criteria
Max Height 3m
Brace cam be bolted to pile or bearer
above ground for bottom bolt
Within 150 of u/s of bearer
10-45 deg angle
M12 bolt (std fixing) or 12 kN alt
© Unitec New Zealand

31. Subfloor - Advanced Braced Piles:
Two adjacent piles connected to each other with a diagonal timber brace
Installed deeper than ordinary piles
Work as pair to provide resistance to lateral (horizontal) loads.
Braced Piles
Two adjacent piles connected to each other with a diagonal timber brace
Deeper than ordinary piles 450mm, Same plan area as table 6.1
Work as pair to provide resistance to lateral (horizontal) loads.
One braced pile footing can work in both directions and have a brace in both “X” and “y” directions e.g. corners
© Unitec New Zealand

32. Subfloor - Advanced Pile/bearer connections for an anchor pile system
Pile\bearer connection for a braced pile system
Review Slide
© Unitec New Zealand

33. Subfloor - Advanced Foundation Walls
Foundation walls are continuous concrete or masonry walls on strip footings that support a building (generally the perimeter).
The internal part of the subfloor is still made up of piles.
Foundation walls can be low height walls (Figure 6.11) or as high as 2600.

34. Subfloor - Advanced
Foundation Walls can use subfloor jack framing to reduce height of foundation wall
Often used on steep sites
Up to 2.0m high
Reinforced concrete masonry or poured in-situ reinforced concrete.
Detailed under NZS 3604:2011
© Unitec New Zealand

35. Subfloor - Advanced Lateral support for foundation walls
Lateral support for foundation walls
Where the top of the foundation wall is not connected to the floor framing,
it shall be one of the following two systems:
A cantilever foundation wall
(b) A stepped footing, see above
© Unitec New Zealand

36. Subfloor - Advanced Standard Foundation Walls
Foundation walls can be made without a cantilevered footing.
In-situ poured concrete or concrete masonry can be used to support timber floors, with a 2.0m max height (not a full floor)
For full Reinf. Conc. Masonry buildings you can use NZS 4229.

37. Subfloor - Advanced Cantilevered Foundation Walls
NZS 3604:2011 sets out criteria
Foundation walls can be used as subfloor bracing unless:
Openings are over 600mm wide
Wall length is shorter than 1500
Either poured insitu concrete or concrete masonry construction.
Can be up to 2.0m high and reinforced as shown in
NZS 3604:2011 Fig. 6.13

38. Subfloor - Advanced
Conc. or Conc. Masonry Fdn. walls can be designed as per Section 6.11 FDN. only (restricted to 2m min. height)
A full storey can be designed in Conc. Masonry only using NZS A full storey a fully reinf. conc. floor is SED.
© Unitec New Zealand

39. Content Review What is the alternate uplift rating for an anchor pile?
What is the maximum height of an anchor pile?
How close to the ground can the bottom of a diagonal timber brace be placed?
What is the maximum height of a concrete foundation wall?
What is the min. width of the footings of a laterally un-reinforced foundation wall?
© Unitec New Zealand

40. Subfloor - Advanced What are the implications of this lecture topic?
All students from different diplomas will need to understand the principles of timber subfloors whether they be technicians, quantifiers, or managers.
There is a quiz based partially on this topic that forms part of the assessment criteria for this course. This is a non-marked, formative quiz but needs to be undertaken and passed to allow the student to sit the test. Students can attempt this quiz as many times as needed to pass.
There is a POE exercise based on this lecture topic and it is suggested that it is undertaken as quickly as possible while the material is fresh, and before the next one is given out.
If you have struggled with answering the lecture review questions or not
understood parts of this lecture, then further reading is recommended – see the notes on moodle and related publishings.
© Unitec New Zealand

41. THE END
© Unitec New Zealand