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  1. #1
    vGolfer is offline Senior Member
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    Default Bearer & Joist dimensions for Sub-Floor

    I have finally found someone to do my sub-floor. basically need to have new bearers, a few concrete stumps and new joists. The company doing the work has told me it will be cheaper if I get the wood myself.

    I have been told to use F17 hardwood bearers and joists. The rooms are no more than 4m x 4m. We are having Yellow Tongue laid on top of the joists and then Sydney Blue Gum glued and secret nailed to the Yellow Tongue.

    In 3 of the rooms (about 4m wide) there was only one bearer running down the centre of the room. Span from the wall plate to the bearer is just over 1800. One guy told me that it would be OK to keep one bearer but I should probably consider having 2 bearers in each room so the span between bearers is closer to 1250 rather than 1850.

    I just wanted to find out what dimension bearers and joists I should use, what lengths they come in and whether I should throw in the extra bearer in each room.

    Cheers

  2. #2
    Gaza is offline Hammer Head - 1K Club Member
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    in Syd we use F14 HWD

    100x50 joists @ 450cc
    100x75 beares @ 1800cc

    my dad who did build in melb said he used the same sizing as we do up here.

  3. #3
    glock40sw's Avatar
    glock40sw is offline Hwd Flooring Manufacturer
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    Ditto what Gaza posted.

    F14 Hardwood is fine.
    However, If you are talking Victorian Ash you may need F17.
    Vic Ash is craap. Just like Tas oak.

    Hooroo.
    Regards, Trevor.
    Grafton.
    Home of the Spotted Gum.

  4. #4
    Skew ChiDAMN!!'s Avatar
    Skew ChiDAMN!! is offline Dances with splinters
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    Ditto that ditto.

    Personally I recommend adding another bearer; especially if you've some heavy furniture. 1250mm spacing is a wee bit further than I'd like to see but it's a vast improvement over 1850!
    I may be weird, but I'm saving up to become eccentric.

  5. #5
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    ditto that ditto . Pretty standard even here in Tassie . Dont try to skimp or save money here as all will be revealed in future squeaks and groans .

    Rick
    No lead paint in my cradle

  6. #6
    Gaza is offline Hammer Head - 1K Club Member
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    brain wave,

    why not use "REd Alert" ie H2 treated LVL B&J, this stuff is same sizes as hardwood but spans better plus no termite problems,

    In Vic use nothing less than F17 as your "green hardwood ie F8 / F11" is rubbish F14 DPR (Nth Coast NSW & Sth east qlds species) is the best stuff if you can get.

  7. #7
    Ziggy's Avatar
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    Vgolfer,

    Sorry to answer your question with a question... but why was it necessary to use the yellow tounge AS well as your timber flooring? Most cases I have seen this done is when the bearers/joist run in different directions to how you want the floor to run (in which case you are changing these now), or on top of a concrete slab, or its a floating floor maybe? Just seems like extra expense if its standard 19-22 mm thick flooring etc..

    Cheers,

    Ziggy

  8. #8
    vGolfer is offline Senior Member
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    Quote Originally Posted by Ziggy
    Vgolfer,

    Sorry to answer your question with a question... but why was it necessary to use the yellow tounge AS well as your timber flooring? Most cases I have seen this done is when the bearers/joist run in different directions to how you want the floor to run (in which case you are changing these now), or on top of a concrete slab, or its a floating floor maybe? Just seems like extra expense if its standard 19-22 mm thick flooring etc..

    Cheers,

    Ziggy
    Ziggy, this is what we have been advised by a few different suppliers. We are getting Sydney Bluegum 130mm width boards, 19mm thickness.

    Some tradeys have asked why we aren't just nailing the boards straight to the joists. We also have some friends that did nail the boards straight to the joists and they regret it now.

    Apparently apart from there being less 'bounce', it is also less 'noisey'.

  9. #9
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    Dusty is offline A1 FLOOR SANDER
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    vgolfer.

    Back to your original query, don't be at all suprised if the chippies do your joists at 650 centres, for the partical board.

    Strip flooring over the joists requires the 450 centres, whereas they are allowed to go wider for chipboard.

    I think Ziggy has pretty well hit the nail on the head (old flooring pun ) as to why pay the extra bucks for the partical board, when fixing directly to the joists is just as good. Despite what your friends have mentioned regarding noise and bounce.

    Also, for my money, I'd have second thoughts about secret nailing 130 mm boards. Face nailing will keep it down flater for a lot longer. 130 mm represents a lot of cupping surface, particularly with a swamp timber like Blue Gum.

    Anyway, it will still come up a treat. Blue Gum's a pretty cool looking timber.

  10. #10
    ausdesign's Avatar
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    F17 joists is the possibly the most common seasoned timber being nominated by designers.
    The joists must be at 450 centres with yellow tongue but having said that the extra support from the additional flooring may assist - but i'd stick with 450. [& probably so will PanelFloor for warranty]
    F17 will span 1800 [single span] & 2100 [continuous span]- supporting floor loads only.
    The important part is what distance the existing bearer is spanning i.e. the stump spacings.
    For example its possible to use 200 deep joists and span a long distance between bearers, but the bearer size & span may not support the additional loads.
    'At the end of the day' you need to work backwards from the existing stump spacing.
    Peter Clarkson

    www.ausdesign.com.au

    This information is intended to provide general information only.
    It does not purport to be a comprehensive advice.

  11. #11
    vGolfer is offline Senior Member
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    Thanks ausdesign. We are actually having new stumps put in. The old brick piers are pretty much gone and at either end there is a wall plate (brick ledge which is part of the foundation of the house which the end of the joist sits on).

    Just a couple more q's.

    1. Two floor guys each said we shouldn't use the wall plates anymore. They suggested we should put a bearer along each outer wall just net to the wall plate. The reason they have said this is we need the floor raised just a touch and it's the best way to get the levels spot on. If we used the wall plates, we would have to use packers under the joists along the wall plate as it would cost a fortune to have a wall plate cut to a specific height.

    They have strongly advised not to use packers to get the levels right along the outer walls. Any thoughts?

    2. With the stumps, what is the recommended spacing? I am just concerned these guys are quoting me more stumps than I actually need.

    Thanks for the help guys...

  12. #12
    ausdesign's Avatar
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    I'm a little confused with the reference to wall plates. It sounds like there are walls below supporting the joists ??
    Any way - F17 bearers supporting floor loads only:
    If using 2/90*35 with a floor load width of 1800 (the sum of half the joist spans either side of the bearer) single span is 1600 and if bearer spans over 2 or more stumps (continuous span) then 2 met. i.e. stump spacings of 1600 or 2000.
    If using 2/90*45 single span 1800 & continuous 2100.

    F8 hardwood bearer will span 1300 single & 1700 continuous
    F8 100*38 joists at 450 centres will span 1500 single & 1700 continuous
    F8 100*50 joists ditto will span 1600 & 1900.

    These are max. spans for normal floor loads so if your thinking of putting a water bed in the room or a heavy bar fridge to watch St Kilda tonight (they might be fast workers) then you'll need to beef up the sizes.

    I'm incomunicar.... I'm away for the next week trout fishing so I hope it all goes well.
    Peter Clarkson

    www.ausdesign.com.au

    This information is intended to provide general information only.
    It does not purport to be a comprehensive advice.

  13. #13
    vGolfer is offline Senior Member
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    Thanks. Just a little confused!

    I am working on 450mm spans for my joists and about 1500mm spans for my bearers. Just want to know the space between stumps.

    If I said 1500mm between stumps, would that be safe?

  14. #14
    ausdesign's Avatar
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    Thats alright - I know what I mean.!!!

    I assume that your looking at stump spacings in line with the bearer being 1500 & that you want to know the stump spacing along the joist direction ??
    If this is so, it is the 'joist span distance' that you are looking to determine.
    F8 100*38 joists at 450 apart will span 1500 single or 1700 if continuous
    F8 100*50 joists ditto will span 1600 single or 1900 continuous.
    -that then gives you your stump spacings in the direction that the joists run.
    i.e. where using short 100*50 lengths of joist that only run from one bearer to the next then the stump spacing would be 1600. When using long lengths of joists where they span over 2 or more bearers (in one piece) the stump spacings would be allowed to be 1900.

    90*35 F17 joists at 450 centers (apart) will span 1600 single span & 1900 if continuous over 2 or more bearers.
    90*45 F17 joists at 450 centers (apart) will span 1800 single span & 2100 if continuous over 2 or more bearers.
    Peter Clarkson

    www.ausdesign.com.au

    This information is intended to provide general information only.
    It does not purport to be a comprehensive advice.

  15. #15
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    Iíd go 1800Cs itís legal (Legal mean you donít need better) and if there a bit over 1800Cs use the F 17 even go 125x75 (they might of said use F17 because itís a bit over 1800Cs) it will be much cheaper since you wonít need more piers. More piers, means more digging, more concrete, more time and the big one more money! Australian standards are among the best in the world, way waste you money!<O</O

  16. #16
    attie is offline Member
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    Quote Originally Posted by vGolfer
    Thanks. Just a little confused!

    I am working on 450mm spans for my joists and about 1500mm spans for my bearers. Just want to know the space between stumps.

    If I said 1500mm between stumps, would that be safe?
    Greetings guys
    This is my first post here so I had better introduce myself. My name is Wayne, I'm a retired builder who worked in the Whitsundays and now cook fish and chips here in Mackay, Queensland. Not realy old enough to retire and intend to build a house and some units for myself shortly but because I've been out of the game for 10 years I'll surely have some questions for you.

    Golfer, the old rule of thumb when using F14 plus hardwood bearers and joists was - "1/2 the span plus one"
    eg. Joists, 1500 span [5 ft.] 1/2 = 2 1/2" so say 3" plus 1 = 4" x 2" [100 x 50]
    Bearers, 1500 span [post to post] as above x 3" [75] = 100 x 75

  17. #17
    vGolfer is offline Senior Member
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    Thanks very much for the info everyone. Much appreciated.

    I have had about 3 blokes come over to give quotes on the sub-floor - ie rebuild the bearers and joists with stumps underneath. Just to set the scene, it's an old single fronted solid brick Victorian home in Melbourne. The joists sit on bearers in the middle of the rooms and wall plates along the edge of each room.

    We need our levels brought up about 20mm throughout the house. One guy suggested doing bearers parrallel and close to the walls as well as in the centre of the rooms. He also wanted to put bearers right down the hallway which is about 12m long but only 1.35m wide. This seemed like overkill to me. It's going to be a lot more expensive as we'll need more wodd and a heap more stumps.

    What do you guys think?

  18. #18
    vGolfer is offline Senior Member
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    Just following up on this thread...

    Just wondering what the standard is for flooring? We're getting floorboards laid down a hallway and an open plan area but carpet in the bedrooms.

    The people laying the floorboards are saying that the cleats they use to nail in the florboards grab much better into ply than they do into the yellowtongue. I guess that sounds right but just wanted to get some advice as to what may be the pros and cons between yellowtongue and ply.

    Thanks

  19. #19
    Skew ChiDAMN!!'s Avatar
    Skew ChiDAMN!! is offline Dances with splinters
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    One thing I've noticed, most of the replies here deal with the bearer spans. 1800mm between stumps along the bearer is acceptable, provided the bearers are of acceptable quality. ie. low-end F17 or top-end F14. (Just 'cos a piece of wood has a rating doesn't mean it didn't just barely meet the required specs... waht's deemed acceptable seems to be lower'n'lower quality with every passing year.)

    But, IMHO, the joist span ie. the spacing between each bearer should be less, more like 1200mm. So the stumps would be set in a 1800x1200mm grid. Next thing you know, people'll be saying the joists should be spaced at 1800mm. Sheesh!
    I may be weird, but I'm saving up to become eccentric.

  20. #20
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    You say youíll be carpeting the BRĒs, why not take that coin and buy nice floor boards for the whole house.

    P.S. I,ve never heard of anyone having any trouble with a house built to Australia standards. Why go better?

  21. #21
    attie is offline Member
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    "But, IMHO, the joist span ie. the spacing between each bearer should be less, more like 1200mm. So the stumps would be set in a 1800x1200mm grid. Next thing you know, people'll be saying the joists should be spaced at 1800mm. Sheesh!"

    With respect, you should have been taught at tech. how to calculate spans and load bearings. A high set home is a typical example of pratical use of materials. If your bearers were to be 1200 apart a 75 x 50 joist would be sufficient

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