How To Install A Solid Wood Floor
May 5, 2009 DIY tips, how to, solid wood floors, wood flooring
If you have purchased a solid wood floor then there a variety of ways that theses can be fitted. The one thing to remember is that solid floors cannot be floated under any circumstances. There are many companies that will tell you it is suitable, but in my experience it will eventually fail and start to cup and curl. This is because solid wood is prone to a large amount of expansion, these types of floor need to be directly bonded to the sub floor by either nailing or gluing down.
If your sub floor is a screed or concrete type then you should first check for any moisture or dampness within the slab to do this use a moisture meter with concrete probe, we use a Tramex meter. If you do not have access to a moisture meter and are unable to ascertain weather the slab has a damp problem, then for piece of mind it is a good idea to apply an epoxy barrier. We use and recommend Bona R410, to act as a moisture barrier you will need to apply two coats with a roller and allow 24hrs between coats. You should always apply your moisture barrier from wall to wall and take it approx 60mm up the wall as well to create a complete seal. If your floor is damp to the touch then a moisture barrier will not adhere to the sub floor, in this case seek professional advice (you may have a split pipe or a high water table coupled with a defective slab).
If you choose to install the floor by gluing it down, then you must ensure that the slab is completely level and flat. To do this place a 1800mm spirit level on the floor, if there are gaps greater than 2mm over 800mm between level and the floor, then the floor will need latex levelling.
When you have a level surface you must now undercut all of the door frames, nule posts (nule posts should only be undercut by 10mm anymore will make the post unstable) and architraves. It is very important do to this as it enables you to archive a seamless finish; it also allows an expansion area for the timber. We do this using an undercut saw, which is basically an upside down circular saw with a height adjustable sole plate, this allows the correct height equal to that of the finished floor level to be undercut and removed. If you do not have an undercut saw then the best alternative would be to use a small piece of flooring, this will give you the correct height you can now undercut this using a small handsaw resting on top of the flooring. Make sure you only undercut as far as the flooring is going to go i.e. if your floor finishes at a threshold to a kitchen for example, only undercut up to the end of the door stops. Remember you must always leave 25-30mm gap between an existing floor i.e. tiles and your new floor to allow a graduating door bar to be fitted.
Use a very sharp chisel to remove the piece of wood that you have undercut/frame by gently chiselling away at it bit by bit, this does work but takes care and time. When you have under-cut fully use a narrow chisel (narrower than the cut you have made) to ‘knock out’ the pieces of frame/wood, make sure you have removed all that you can, the more you remove now the easier it will be to install the floor later.
You are now ready to start installing your floor….
First decide on the direction that you want the floor to run in, bear these few points in mind before you make your decision. Try to start from the longest, straightest wall, ideally form the door way side. If there is no doorway on the longest wall but there is a radiator or pipes coming out of the floor then start from this wall (it is much easier to do the radiator cuts or doorway cuts on the first row than it is on the last). Do not attempt to start the flooring with a broken line i.e. trying to go round a fire place or large obstacle, we do sometimes do this but it takes a bit of practice and patience to get it right.
There are two ways in which you can fit solid wood flooring, (the method of use will be dependent on type of sub floor you have);
- By secret nailing directly to joists or at 90 degrees to existing floor boards using a Porta nailer or compressed air nailer. If you choose the nailing route there are a few things you need to consider. Firstly make sure your nails do not project more than 2mm below the sub floor you are nailing into, porta nails are available in 1½ inch 1¾ inch and 2 inch. The length is important because you do not want to hit any pipes or cables that may be directly underneath the floor. Secondly you should be aware that you will have to face nail i.e. through the top of the board for the first and last two rows, as the angled porta nailer will not fit in. Thirdly floors that have been nailed down are prone to squeaking, this probably won’t happen for many years but when it does the only way to resolve it is to nail through the face of the board. Obviously you run the risk of hitting a pipe or cable in doing this; however this can be avoided if you draw a floor plan when installing the floor.
- By gluing directly to a concrete or ply/chipboard floor. Few things to consider here, personally if the sub floor was ply or chipboard then I would secret nail it. If you nail into chipboard then you will have to put a fixing every 150mm. This is because chipboard is a particle board, as the nail goes in it almost causes the back of the chipboard to explode out; we double the amount of fixings we put in to compensate for this. A Couple of points to be aware of when gluing. Always use glue that is recommended for the installation of the board that you have purchased, for example Bona S760 is a solvent based glue and is only suitable for boards up to 150mm in width. For boards over this use either Bona R850 or Sika T54/T52.Moisture is a huge issue when you glue a floor directly to a concrete slab, this is because wood is hydroscopic meaning that it will adapt to its environment by absorbing moisture. If you suspect moisture is present always use a meter to check the levels, levels for fitting directly onto concrete should be below 25% RH. If the levels are above this but below 75% RH then a Epoxy barrier can be applied, see previous blog post.
Flooring adhesives are split into 3 categories:
- Firstly there are solvent based glues, these tend to be the cheapest (expect to pay £50 for 13kg tub) and quickest drying but have limited uses i.e. they can only be used on boards with a width less than 150mm and not in the presence of under floor heating.
- Secondly you have non solvent adhesive, these are the most commonly used, this is because they have a longer ‘open time’ are easier to trowel out and work with. They are generally a lot more expensive than solvent based, expect to pay £80 for 15kg tub (1kg of adhesive will cover 1sqm of floor), however they are more versatile and can be used to bond boards down up to 220mm wide.
- Thirdly there is non solvent gun applied adhesive. This is the same as above but is used in bulk guns to apply adhesive on to Sika silent layer, this is an underlay mat used to take up small deviations in a floor as well as adding insulation and the use of less glue. The mat layer has small holes cut into it where the adhesive is dispensed into, we use either Bona 600cc sausages or Sika T2, both are very similar, expect to pay £12.00 per sausage and £35.00 for the dispensing gun (one sausage will cover approx 1-1.5sqm).First trowel your glue out using a flooring trowel. Lay the first line of boards down with the groove in the board facing the wall, ensure that you have 80% glue coverage on the back of the boards and no hollow spots. When you get to the end of the line you will need to cut the final board in, this can be easily measured as follows; If you have a tongue on the board that is laid on the floor, you need to place the final board with its groove end against the wall you are going to finish on. Leave a 10mm gap between the groove end and the wall; now mark off what is to be cut off by marking a line on this board in line with the end of the board that is on the floor. I know it sounds confusing but it really isn’t too difficult, if you are unsure use a tape measure to check your measurement and then use the off cut to start the next row.
When you are gluing floors it sometimes necessary to strap the floor with compression straps to ensure that all the gaps in between the boards are closed up, these normally only need to be used for the first three or four rows, after this the flooring should be all aligned properly.
It is also a good idea to leave weight on the floor that you have just laid to ensure that it bonds to the sub floor properly; you can use the flooring that you have not laid as weight, or any un-opened tubs of flooring adhesive.
Be sure to remove any spillages of adhesive before they dry, this particularly important when fitting an oiled floor using Sika T54. Sika is a very good adhesive but incredibly difficult to remove when dry, it is so strong that if you try to remove a board when the glue has cured it will either leave large splinters of wood on the floor or bring the screed/latex up with it. It for this reason that as a fitter I no longer use Sika T54, we now use Bona R850, this adhesive can be removed with water when wet and with UPVC solvent cleaner when dry. Although not as strong as Sika, it still has plenty of ‘grab’ and if you do need to remove a board or re-position it normally it will leave the screed/latex intact.
When you get to the last three rows make sure you have troweld all your adhesive out right up to the edge of the wall, this will make it easier when fitting the last two rows as you will not be able to fit a trowel in. As with all the boards measure twice cut once, there is nothing worse than trying to re-cut a board when it is covered in glue.
Once finished leave some weight on the last few rows you have just laid. Leave all your expansion wedges in as well as adding some behind the last row you laid to ensure that the floor does not move when drying. Leave the floor un-trafficked for 24hrs then go in and remove all the expansion wedges, stand back and admire your hard work, knowing that because you followed my guide you will have a beautifully fitted wood floor to admire for many years to come.
For any more information please contact Gavin at Floorcraft in Farnborough, UK (+44 (0)1252 372227) or visit us at www.floorcraft.uk.com
Tags: Bona R410, DIY guide, Sika T54, solid wood flooring, Tramex meter
