Browse Forums Flooring & Floor Covering 1 Mar 28, 2010 11:18 pm Hi, I am looking at installing timber floors in a house I recently purchased. The house is on a concrete slab. I have removed some existing tiles which has left some of the tile glue/mortar on the concrete. I have been told that the glue needs to be completely removed if the boards are to be glued directly onto the concrete. I have also been presented with the option of plywood underlay, which would not require the mortar to be removed. Other installers have have quoted me for a flywood installation without asking me of the condition of the subfloor.. What are the pros and cons of installing directly onto concrete and using a plywood underlay? I have also read about acoustic underlays. Which would be a better installation, and what other options do i have? I would like to have this done right the first time. Any advice would be much appreciated. Thanks in advance. Erz. Re: underlay for solid timber floors on concrete slab 2Mar 29, 2010 6:31 am The two different methods your talking about are direct stick (the timber is glued direct to the concrete) as opposed to fixing the timber to a sub-floor (ply or battens) Direct Stick. The slab needs to be cleaned with chips and glue etc scraped off (you could possibly hire a machine to do this) and then levelled with a self levelling compound. Then you need to waterproof the slab with either plastic sheeting or a VBS (Vapour Barrier System) Selleys VBS is the go. Once that is all sorted you can direct stick the flooring using Selleys Direct Stick, however you do need to be on top of clamping and weighing the floor down. Over all this is do-able but can be complicated. Sub-floor. Once again the floor needs to be cleaned, particular if your subfloor is ply (battens can be a bit more forgiving), and similarly you need to waterproof (actually Vapour proof - as you are stopping moisture coming up through the slab into your flooring) the slab. The battens or ply are then fixed perpendicular to the way you want to lay the boards. And finally you can secret nail and trowel glue the boards down. Cheers Re: underlay for solid timber floors on concrete slab 3Mar 29, 2010 9:33 am I never liked the concept of direct stick to concrete with the exception of slim parquetry. In the unit I'm renting now this is the way it has been laid (not sure it is to concrete). Next to the balcony door and the floor-to-ceiling windows varnish had cracked due to the movement of timber and there are quite noticeable gaps - all thanks to the moisture timber sucked when it was raining... During the periods of heavy rain we had in Feb a few planks sprang out and wouldn't go back until release the moisture. The affected part will need to be re-laid in order to look good. With plywood and battens - there are different things to consider. Plywood while costs more (~$50 for a 2400x1200x15 mm sheet) provides more flexibility when nailing floorboards and better acoustic characteristics. Battens are cheaper but will restrict the minimal size of a plank you will be able to use (i.e. if your battens are at 60 cm away, the minimal length of a floorboard will have to be 65 cm and therefore, the %% of waste will be higher). I also read that the sound can be more hollow as well as opportunity for squeaks to be higher. ... built a Promenade with Clarendon. viewtopic.php?f=31&t=25104 20-10-09 - excavation and piering completed ... 12-04-10 - Basins fixed. Connecting to the electrical grid 23-04-10 - PCI 07-05-10 - HANDOVER! Re: underlay for solid timber floors on concrete slab 4Mar 29, 2010 9:57 am Direct Stick has become quite common. It is largely pioneered in WA where there are many more slabs because of the sandy soil. It is a very legitimate installation method, however process is critical. Vapour treatment of the slab and trowel spreading of glue are imperative. Whilst it would seem cheaper to pursue direct stick, I tend charge more than other methods as it is a much more labour intensive process. Particularly if the flooring needs to be clamped in anyway. EB. I suspect the parquetry springing is not related to its installation, but moreso the introduction of water to the flooring. Any timber floor which has a regular ingress of water will fail in some way eventually Cheers Re: underlay for solid timber floors on concrete slab 5Mar 29, 2010 11:25 am Thanks for the replies. From what I gather, Direct stick seems to be pushed as a cheaper installation method. Although one installer said he would charge me the same as he would use less glue if he nailed plywood to the concrete as an underlay. This sound right? He also suggested if I go with 12mm plywood, I should for 19mm floorboards. I was also told that putting a plywood underlay onto the concrete would make it feel more like walking on floating floorboards. A little hard to decide which installation method I should ask for, with each installer suggesting something different. Would anyone have any recommendation on a place to purchase the timber? I have been quoted a decent price from Mountain Timber Products, but again one installer didn’t sound too impressed with the place. Not sure if he just wanted me to purchase off him... Thanks again. Re: underlay for solid timber floors on concrete slab 6Mar 29, 2010 11:51 am erz Thanks for the replies. From what I gather, Direct stick seems to be pushed as a cheaper installation method. Although one installer said he would charge me the same as he would use less glue if he nailed plywood to the concrete as an underlay. This sound right? He also suggested if I go with 12mm plywood, I should for 19mm floorboards. I was also told that putting a plywood underlay onto the concrete would make it feel more like walking on floating floorboards. A little hard to decide which installation method I should ask for, with each installer suggesting something different. Would anyone have any recommendation on a place to purchase the timber? I have been quoted a decent price from Mountain Timber Products, but again one installer didn’t sound too impressed with the place. Not sure if he just wanted me to purchase off him... Thanks again. Try MYM Timber in Keilor for flooring materials. Re: underlay for solid timber floors on concrete slab 7Mar 29, 2010 12:17 pm erz ......Direct stick seems to be pushed as a cheaper installation method........... Although one installer said he would charge me the same as he would use less glue if he nailed plywood to the concrete as an underlay. This sound right? He also suggested if I go with 12mm plywood, I should for 19mm floorboards. I was also told that putting a plywood underlay onto the concrete would make it feel more like walking on floating floorboards. A little hard to decide which installation method I should ask for, with each installer suggesting something different. Would anyone have any recommendation on a place to purchase the timber? I have been quoted a decent price from Mountain Timber Products, but again one installer didn’t sound too impressed with the place. Not sure if he just wanted me to purchase off him... Thanks again. Quite a few questions in there!! As I mentioned earlier, personally I charge more for a direct stick job as it is more labour intensive and riskier regarding potential call backs. I use the same amount of glue regardless of the installation method. All floors should be fixed with trowel glue. Although I use two different types -= for direct stick I use Selleys Direct Stick and for a ply subfloor I use Bostick Ultraset - both trowelled on. In regard to the thickness of the boards it is quite reasonable to install overlay (thinner boards) over a slightly thinner ply - the difficulty is finding the correct size staples for the secret nailing. The problem with thinner ply and/or boards is that you need to pay more attention to the levelness of the slab as any troughs and hills are transposed more starker through thinner boards. As for every installer having a different opinion - welcome to timber flooring Wherever you purchase timber from, you should be able to identify chain of custody details for your timber and clarify the state of your flooring (kiln dried, treated, which grade etc) Re: underlay for solid timber floors on concrete slab 8Mar 29, 2010 3:25 pm erz Thanks for the replies. From what I gather, Direct stick seems to be pushed as a cheaper installation method. Although one installer said he would charge me the same as he would use less glue if he nailed plywood to the concrete as an underlay. This sound right? He also suggested if I go with 12mm plywood, I should for 19mm floorboards. I was also told that putting a plywood underlay onto the concrete would make it feel more like walking on floating floorboards. An Extract from ATFA Timber Flooring Manual V2: Quote: Fixing recommendations - plywood sub-floors to concrete slabs and flooring to plywood Plywood sub-floors should be structural grade, a minimum 15 mm thick and with a type A bond. Plywood 12 mm thick in also used by floor installers but with this thickness greater consideration needs to be given to slab evenness and the possible perforation of moisture barriers beneath the plywood. Quote: Would anyone have any recommendation on a place to purchase the timber? Do your research. I sourced mine from North River Timbers. There are should be plenty of good suppliers. ... built a Promenade with Clarendon. viewtopic.php?f=31&t=25104 20-10-09 - excavation and piering completed ... 12-04-10 - Basins fixed. Connecting to the electrical grid 23-04-10 - PCI 07-05-10 - HANDOVER! Engineering timber is certainly a less fuss option, times cheaper to supply and install and better withstands humidity. 1 15924 Hi l plan to install a self adhesive vinyl plank floor. l first need to attach masonite boards underlay to by plywood subfloor of my house. What size nails and how many… 0 8379 Jimbo73 I would use heaps of adhesive on each sheet and screw rather than nail. use as many as you like cheers Simeon 1 4075 |