Browse Forums Building Standards; Getting It Right! 1 Jul 08, 2013 10:56 am Hi All, If I am placing my floor bearers directly to the slab, does it matter what size I use? I plan to just use the size needed to get my floor joists at the right height. Most likely use 100 x 75 Joists. They will only need to be raised about 50mm to clear the plumbing. Any help would be great. Re: Bathroom SUBfloor advice - Bearers directly on slab 2Jul 08, 2013 12:28 pm No it shouldnt matter because its on a slab. Normally bearers sit on point loads (stumps, piers) but because its on a slab and now a universaly distributed load I dont see why not. Re: Bathroom SUBfloor advice - Bearers directly on slab 3Jul 08, 2013 12:43 pm Thanks Robbie, Theoretically I could use any strong material to sit the Joist on as well then and not necessarily use full length bearers? ie: like small pillars. I will be inserting noggins between the joists to maintain the spacing and vertical stability. Re: Bathroom SUBfloor advice - Bearers directly on slab 4Jul 08, 2013 12:48 pm Yes your right. The main thing is what ever you use as a bearer is fixed to the slab properly and your joists are in accordance with the timber framing manual. I dont see why you dont just use joists without bearers?? Re: Bathroom SUBfloor advice - Bearers directly on slab 6Jul 12, 2013 7:48 pm You could use L brackets but if you are lifting them 110mm to the under side they would be a bit flimsy. You could make or have made some mini sort of stirrups, Just a "U" shape to bolt down first, then bolt through once the joist is lifted to height. If you didnt like the bracket idea, a cheaper way than bearers would be bolt down a piece of 70 x 35 for EG, then nail another 2 pieces of 70 x 35 on top so you effectively make a 70 x 105 bottom plate running on the slab. This would cost around $6m versus $nearly $20m for a solid H'wd bearer. It all depends on the size of the area you have to do I suppose. You could also cut your joists down to 100 x 50 or even 75 x 50 if you put your bearers or bottom plates closer. Just a question, is the slab a structual slab and does it have a vapour barrier installed? Re: Bathroom SUBfloor advice - Bearers directly on slab 7Jul 12, 2013 8:03 pm Hi 33amc, Not structural, not sure about vapour barrier. There is already a raised floor next to it. So I have decided to just copy it's construction. Has Bearers and joist construction. Do I still have to secure the bearers to the slab? I do like the 2 x 75 x 35 method. What grade of timber should I use for that. The area is only 1800 x 2400 approx Re: Bathroom SUBfloor advice - Bearers directly on slab 8Jul 12, 2013 8:57 pm 33amc has made a good point about vapour barrier It is always good idea to isolate timber from concrete with flashing or malthoid and pay attention to sub floor clearance and ventilation. If you get dampness or trap dampness you will get rot and increased termite risk Foremost Building Expert in Australia,assisting with building problems/disputes, building stage inspections,pre-contract review advice for peace of mind 200 blogs http://www.buildingexpert.net.au/blog Re: Bathroom SUBfloor advice - Bearers directly on slab 9Jul 13, 2013 7:37 pm Firstly dont use unseasoned timber, so that rules out 100x75, 75 x 38 etc If you use unseasoned timber it can shrink up to 5mm, and thats something you dont want on any internal room let alone a bathroom. This could lead to tearing the waterproofing and grout cracking etc. secondly, if there isnt a vapour barrier, this is a real consideration. The best fix would be to waterproof the slab first, this is a fix for the rising damp which many underestimate, especially through a slab. If you want to save costs or run the risk of durability of the timber, use a treated pine or seasoned H'wd. If you are going to use 70x35bottom plates stacked up as I suggested, make sure the final plate which will bear the joists is a mgp15 grade. This will give better resistance to compression from the floor load. I would run 3 rows of plates or bearers. Also, if you dont want to waterproof the slab also consider painting the underside of the floor sheeting or using CFC. what flooring did you have in mind? Andrew XCEM Alpha flooring seems to relatively new and I could not found any reviews. Have you or someone you know have used it and would recommend over other subfloor options?… 2 7578 Jimbo73 I would use heaps of adhesive on each sheet and screw rather than nail. use as many as you like cheers Simeon 1 4046 Would also like an opinion from anyone that has used xcem over hebel for floors. Thanks 1 13279 |