Bearer & Joist dimensions for Sub-Floor

[vGolfer]

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

[Gaza]

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.

[glock40sw]

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.

[Skew ChiDAMN!!]

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!

[rick_rine]

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

[Gaza]

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.

[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

[vGolfer]

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'.

[Dusty]

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.

[ausdesign]

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.

[vGolfer]

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...

[ausdesign]

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.

[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?

[ausdesign]

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.

[Auspiciousdna]

I’d go 1800Cs it’s legal (Legal mean you don’t need better) and if there a bit over 1800Cs use the F 17 even go 125x75 (they might of said use F17 because it’s a bit over 1800Cs) it will be much cheaper since you won’t 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