Hi. I have looked in on various deck threads over last 6 months or so. Starting part of my ground level one this soon. 2.7m by 8m(approx.) with one side attaching to house and one side attaching to existing deck(side frames). Im planning on using 75x50 to attach to those two maybe on low piles as well?. Questions are around pile spacing and joist thickness and spacing please. The decking (90x35) will run out from the house as that is how existing deck is.
I have about 200-250mm above soil. Im thinking 100x100 piles with 75x50 joists on those piles and hanging from an end frame also on piles.
So what spacing for piles please width and lengthwise and will the joist thickness be enough if it sits on the piles. at what centres. Its been 20 years since I built last one(25 m on three levels max height .5m)which I over engineered according to my family.
Ta
spiritofgonzo,
Oct 14, 9:23pm
75x50 joists? Normally joists are around the 150x50 so you can span them a couple of metres, otherwise you’d need a pile every, I don’t know, 1m or so. Doesn’t sound right to me
newtec1,
Oct 14, 9:56pm
For a start the very minimum size for a joist would be 100x50 spanning no more than 1 M,The bearers would need to be at least 100x75 with pile spacings no more than 1M. it is possible to use RS timber to increase the size especially if they are a constant gauge,but i would never use 75x 50 joists.
snoopy221,
Oct 14, 10:06pm
I Tink Ya Should be talkin. To a QUALIFIED builder. K
tezw1,
Oct 14, 10:17pm
Joists could be 90 x 45 H3.2 SG8 spaced at 450mm cts could span up to 1.4m. Bearers would need to be at least 90 x 90 with pile spacing at 1.3m cts. Bearers could be in the same plane as the joists, would just need stainless joist hangers. The top of your piles should be 150mm min above ground level and if less than 300mm a strip of DPC between the top of the pile and the bottom of the bearer. If the deck extends more than 2m from the building or is not connected to the building, then it needs to be braced. Half of the demand of a house floor with light cladding and 0 degree roof.
mtbotrev,
Oct 15, 8:49am
Im happy to show my ignorance and seek advice here thanx.
mtbotrev,
Oct 15, 8:52am
Cheers. I see the message about joist size as 150x50 comes thru later as well.
happychappy50,
Oct 15, 8:58am
You can use 140x45 for your bearers @ 2 mtr centres,then 70x45 for your joists @ .450 centres then your decking boards,that should fit into your requirements,just make sure you have installed sufficient drainage underneath if there could be a problem with ground water,nothing worse than water sitting there that can't get away
mtbotrev,
Oct 15, 9:00am
Thanx newtec1. I don't have enough height to use bearers(without excavating and 8mx3m area) so was thinking of the joists as bearers, sitting on or bolted to the piles. Is that okay? It might need closer piles I guess as they are the weight bearers. So that would be 100x75 piles at 1m spacings length wise(8m side) and then say 400mm apart for the 2.7m side with the decking on top. Its a lot of piles tho. 8 over the 8m and maybe 7 over the 2.7m width so 56?
mtbotrev,
Oct 15, 9:06am
Thanx tezw1. The deck is a low level deck from house(wide door) connecting to another low level deck 3m out. height is about 200mm off ground(just rechecked).
I will attach a joist to the house below the door level allowing for the decking on top. Noted re the DPC.
mtbotrev,
Oct 15, 9:09am
Thanx happychappy50. I have remeasured it at 200mm height to play with without major soil removal which then creates ponding area as u suggest. So if I was wanting to(having to) just attach joists to piles and then decking on top what can I get away with that will be solid?
stevo2,
Oct 15, 10:02am
Good advice here. Especially the part about being on one plane which will keep you low to the ground as requested. O.P. PLEASE dont use 70x45. Its commonly only used for purlins these days - never for structural.
happychappy50,
Oct 15, 10:13am
If that is your case OP,tighten up the piers/piles maybe 1.5 & use a dble 140x45 as your bearer,run noggins between to stop twisting & lay your decking over the top,if you are using 30mm thick that should be ok.Also,for your piers have you considered concrete blocks? I used this in a situation a few yrs ago & worked well,just dig your footings 300x300x300 block on top set on the concrete with a strap or some form of fixing into the block for the bearer.
johotech,
Oct 15, 10:48am
Have a look at this blog. It has some good photos. Take note of how the joists are sitting on a bearer attached to the house. That bearer should be spaced off the house with a packer & DPC. https://evcricket.wordpress.com/2012/07/19/building-a-deck/
Lots of good advice above - take note especially of where they are saying SG8 graded timber.
mtbotrev,
Oct 15, 12:20pm
Ta. so if his bearers sitting on the concrete pavers are my joists and his joists are my decking that idea will work?. They run how mine will have to.
Can I get away with that spacing if I use the bigger joists as suggested. at least 150x50 and maybe double thick say one on either side of piles. Original plan was to have those joists sitting on pile to take with down.
tezw1,
Oct 15, 9:30pm
Another option to look at for framing instead of timber would be Qwickdeck - http://www.outdure.com/qwickbuild Probably expensive as hell, I've haven't had a project to use it on.
tezw1,
Oct 15, 9:36pm
That deck was built in Aussie where the building systems are different. Even if you are not getting a building consent the structure is still supposed to comply with the NZ building code. Another option is to pour a concrete pad and then build up off that. I did that last year where we only had 100 to 150mm of clearance. Another would be to pour 150 x 150 strip foundations and lay the joists over these. Use a counterbored ankorscrew to fix to the concrete
mtbotrev,
Oct 16, 9:00pm
Thanx tezw1
tegretol,
Mar 5, 10:42am
Built my deck with 250x50 joists 300 centres on 150mm H5 poles 1200 apart. It feels like concrete and I ain't ever having to worry about fixing or falling thru it.
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