Browse Forums Outdoor Living 1 Oct 03, 2011 10:06 pm Hi all, I'm looking at building a timber deck out of treated pine over my concrete slabbed Alfresco. The deck will also extend out past the slab by two metres over soil. The clearance between the slab and rear entry to the house is only 150mm. Total size of the deck will be 4x7m. The overhang over the soil will be 2 metres. Originally I was thinking of the following sizes for timber: - Bearer @ 90x65mm - Joist @ 40x65mm This would leave me with an extra 20mm for the decking. My question is would this combination result in a safe deck which would last or would I need to decrease my spacing from 450mm to a lesser number? Re: Timber deck over concrete slab 2Oct 04, 2011 11:01 am I wouldn't bother with bearers over the concrete I would sit the joists on packers but bolt down into the concrete. Alternatively use steel angles as bearers which will be smaller than equivalent timber sections. Here is alink to some timber design tables which include decks. http://www.tabma.com.au/resources.php The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: Timber deck over concrete slab 3Oct 04, 2011 11:36 am Thanks Bashworth, I'll need some bearers as the deck is expanding past the concrete slab. I thought of using steel as a bearer but wasn't sure if it would work. What exactly is a steel angle and what does it look like? Re: Timber deck over concrete slab 4Oct 04, 2011 3:59 pm Id use tember bearers for the area away from the patio but you could probably dig out some soil to get the extra depth. This is a link that tells you more about steel angles and other sections. http://www.onesteel.com/images/db_image ... _sep01.pdf The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: Timber deck over concrete slab 5Oct 04, 2011 9:15 pm Hey Bill and Jackki...we will be doing something similar too so interested in how you go about doing this. Just wondering if you can use only joists over the concrete area and then use both bearers and joists over the area where there is no concrete/slab ? 26/2 - Sales 23/3 - Colours 31/3 - Tender 14/4 - Contract 7/5 - Taps 12/6 - Site start 15/6 - Slab 27/6 - Frame 1/8 - Lockup/Fixing 29/9 - PCI 25/10 - Handover Re: Timber deck over concrete slab 6Oct 04, 2011 9:17 pm Madison27AA Hey Bill and Jackki...we will be doing something similar too so interested in how you go about doing this. Just wondering if you can use only joists over the concrete area and then use both bearers and joists over the area where there is no concrete/slab ? Thats my plan, the only issue is moisture. Re: Timber deck over concrete slab 7Oct 04, 2011 9:46 pm Thanks Bashworth. I think I'll probably go with your idea of joists on the slab with packers underneath and then extend it out to bearers and joists over the soil area. Humble, if you're referring to moisture problems between the timber and the slab you could try using Damp Proof Coursing between the two. Should work. Re: Timber deck over concrete slab 8Oct 04, 2011 10:03 pm Bill&Jackki Thanks Bashworth. I think I'll probably go with your idea of joists on the slab with packers underneath and then extend it out to bearers and joists over the soil area. Humble, if you're referring to moisture problems between the timber and the slab you could try using Damp Proof Coursing between the two. Should work. Yup. Still doing the research. The other issue, is sunlight.. and the fading that will occur on the outer deck. My plane is bearers across the slab extending out to the length required, joists on the soil side. Align, and then deck. It should be fine. Dramp Proof Coursing should do the job. Cheers! Re: Timber deck over concrete slab 9Oct 04, 2011 10:13 pm Humble, That is the better option and the way I would've liked to do it. The thing stopping me is the space between the slab and the back door height. just make sure you have enough space to get decent sized bearers and joists in. Oh yeah, don't forget you also need 20mm for the decking too Good luck. Re: Timber deck over concrete slab 10Oct 04, 2011 10:30 pm Bill&Jackki Humble, That is the better option and the way I would've liked to do it. The thing stopping me is the space between the slab and the back door height. just make sure you have enough space to get decent sized bearers and joists in. Oh yeah, don't forget you also need 20mm for the decking too Good luck. I have 135mm.. still building.. so yer miles away. Re: Timber deck over concrete slab 11Oct 05, 2011 8:50 pm Bill&Jackki Humble, That is the better option and the way I would've liked to do it. The thing stopping me is the space between the slab and the back door height. just make sure you have enough space to get decent sized bearers and joists in. Oh yeah, don't forget you also need 20mm for the decking too Good luck. hi BJ. i just finished a very similar deck to what you are planning of doing. See my other thread... I used 90mmx90mm bearers on pryda post anchors that are on concrete posts. then 20mm of window packers under the 90mmx45mm joists on the slab.. L brackets bolted into the slab and the joists. then 140mm x 19mm of decking board for the border and 90mm x 19mm of decking boards.. just waiting for a sunny day to put the decking oil and she should be a thing of beauty also, i had 140mm stepdown to the concrete slab so 20mm (window packers) + 90mm (joist) + 19mm (decking board) and i only got 11mm of step down to the deck. i initially thought that it would still be too hight but now that it is finished, don't even notice it.. hope that helps... Oxford 22 @ Stage12a Point Cook Site Cut : 05/03/2010 Slab Pour : 24/03/2010 Frame Inspected : 06/04/2010 Pre-plaster Inspection: 22/04/2010 PCI: 16/07/2010 Final Inspection: 30/07/2010 Landscaping: who knows??? MyHomeoneThread Our Oxford22 Blog Re: Timber deck over concrete slab 12Oct 06, 2011 10:12 pm Thanks Draco76. Seems packers are the way to go. I'm looking forward to starting this project and will definitely be posting pics. One other thing Draco. What size masonry anchors did you use to bolt the L plate into the slab? I'm afraid that if I go too deep I may hit the waffle. Re: Timber deck over concrete slab 13Oct 07, 2011 7:04 pm hi BJ.. I used 10mmX50mm galvanised bolts.. Oxford 22 @ Stage12a Point Cook Site Cut : 05/03/2010 Slab Pour : 24/03/2010 Frame Inspected : 06/04/2010 Pre-plaster Inspection: 22/04/2010 PCI: 16/07/2010 Final Inspection: 30/07/2010 Landscaping: who knows??? MyHomeoneThread Our Oxford22 Blog Re: Timber deck over concrete slab 15Nov 22, 2011 1:22 pm Hi! I've noticed that most people have ~140mm-150mm step down in concrete slab from indoor to outdoor area. At the moment our builder has supplied a concrete slab for our alfresco which is one brick course down ~75mm. Is this too little to put a timber deck in place? Our sales consultant doesn't seem to think so ... we want a 'seamless' look between indoor and outdoor (minimal step down once all flooring is in place) Building ??? with ??? Re: Timber deck over concrete slab 16Dec 09, 2011 2:50 pm buildingbee Hi! I've noticed that most people have ~140mm-150mm step down in concrete slab from indoor to outdoor area. At the moment our builder has supplied a concrete slab for our alfresco which is one brick course down ~75mm. Is this too little to put a timber deck in place? Our sales consultant doesn't seem to think so ... we want a 'seamless' look between indoor and outdoor (minimal step down once all flooring is in place) im also in a similar boat with the lack of room from sliding door to top of concrete.. i think im looking at approx 60mm! i was going to do 35x90 on flat, with 16mm decking and some 5/10mm packers underneath .. would this cause too much concern for moisture build up? that i my main issue at present Re: Timber deck over concrete slab 17Jan 18, 2012 10:29 am Looking for some more opinions out there? Anyone? Building ??? with ??? One corner of my shed slab will be directly over a 1400mm diameter concrete soakwell. Is it feasible to fill the soakwell with concrete then lay the shed slab over the… 0 665 Much a do about nothing. You can see the fall heading to the actual drains. Stormwater ingress will be minimal and it's far better to have the top sitting flush rather… 12 6249 As most others have posted above the install isn't compliant. 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