Sanding and Sealing Wooden Floors

Now that we are becoming more health conscious and are taking more care about our environment, wooden floors have become fashionable. Allergy sufferers have found that living without carpets can reduce the medication requirements and in some instances children suffering from dust allergies can live medication free lives thanks to living in the cleaner environment that wood flooring provides. The real hardwood floor can be an expensive addition to the house and, even if it is only a good quality laminate floor, the outlay could be high so it is always worth considering whether it is possible to turn the existing floorboards into a liveable floor surface.

Caution: The sanding and sealing of Hardwood flooring e.g Oak,Maple, Beech etc. is not really a DIY (changing rooms type) job unless you have experience using the machinery as it is too easy to damage the floor by leaving roll marks and other sanding marks in the floor.

What this article is about
Providing some useful information on the sanding and sealing process from beginning to end that dispenses with the obvious, like having to remove the carpet, and concentrates on the information that is helpful.

Preparation
As with most projects, preparation is the key to success and with sanding floors this is especially true. Firstly, make sure that the room is empty as this is not the type of work to be undertaken piecemeal. The next thing to do is to punch the nails below the surface of the wood. I have read articles that suggest that this isn't necessary but if you don't there is a risk that a spark will cause the fine dust in the collection bag to ignite (never leave this bag full unattended as they have been known to set on fire). The other risk is that it will damage the not too cheap sanding belts and may even cause rust to appear in the finished sealed floor.
If the wood flooring is in reasonable condition you will be able to get started reasonably quickly but if any are in need of repair or refixing, do this before any sanding work is undertaken. Cupped and warped boards may require additional sanding with the edge sander as the bigger sander won't reach the board surface properly. In cases where the replacement of boards is required it is always better if you can use older floor boards but if you need to use new boards it will probably be advisable to stain the floor to get a more even colour throughout as the new boards will stand out more than you might imagine.  The idea of using stain on the new boards to match the colour of the older boards is a good idea if you have infinite patience and don't mind failing after many attempts. When you apply the sealer to the wood flooring you'll be amazed how what you thought matched is now nothing like. It is probably better to simply use a stain on the whole area of the wood flooring and be done.

Wood filler is made from the dust from the 100 grit sanding process mixed with a solvent based clear filler or a water based filler also mixed with the sanding dust. The filler is applied and then after drying, which usually takes a few minutes, is sanded during the final sanding process just prior to seal/stain application.

Sanding
Contrary to popular belief, the sanding of your wood flooring need not be a dusty hazardous operation. The key to making it virtually dust free is to use the correct machinery. The usual fare offered by most hire shops will not be efficient enough to give you a dust free operation and in the case of people sanding proper hardwoods floors like Maple, Oak etc these machines are almost certain to leave ripple marks in the floor which will be nothing to do with operator error. If at all possible hire a professional belt sander (like an Orebro or Lagler) and avoid using a drum sander which will not help you to achieve a quality finish to your floor. The professional machines mentioned have the facility to remove the sanding belt without having to tilt the machine and provides the operator with much more control over the sanding operation. Another feature of the machines is the belt pressure adjustment so that you can change the pressure applied by the belt to the floor as you move from the courser to the finer papers. Real Hardwood flooring requires a heavy machine to get the job done and these professional machines are the answer.

Now that you have the general idea we can address the detail a little.
Normally we would begin the sanding operation using a 36 grit paper to remove any contamination in the floorboards. Sometimes we may need to begin with a 24 grit paper followed by the 36 grit if the floorboards are cupped or especially dirty. We would use an edge sander for the edges and a smaller detail sander to get into the corners. The operation is repeated using firstly 60 grit paper and than 100 grit paper. It is not possible to leave out any stage otherwise the grain in the wood is not sanded correctly and scratch marks or rough feel will be evident. Following the sanding with the 100 grit paper we would then use a rotary polishing machine with a special abrasive pad to remove the effects of where the edge sander and the belt sander start and finish. This helps to blend in the line left by using the different types of machine.

When using the course paper you may find it helpful to cross cut the floor instead of running along the length of the board. This will usually help in getting the boards clean but will then require you to still sand with the grain along the length of the board. When using the finer grade papers always sand along the length of the board to obtain a proper finish.

Having sanded the floor you will need to apply the finish before too many people have walked footprints onto the floor so don't wait too long.
If you have decided to stain the floor this is when you will earn how good you were with the sanding machinery as any roll marks scratches etc. will become evident with the introduction of the stain. We normally use a spirit based wood dye e.g. Colron or similar when we are sealing the floor with a water based floor sealer. We tend not to use solvent based sealers now due to health and safety reasons plus the fact that the modern water based products are just as hard wearing and quicker in the application. The floor dye should be applied liberally so that it saturates the wood and than any excess removed with a lint free cloth. You will need to wait until the floor is completely dry and we would usually wait for 24 hours to allow the solvent sin the dye to evaporate thereby ensuring that there are no problems with the adhesion of the floor sealer.

Sealing
Applying the seal to the wood flooring can be done in a variety of ways but, whichever method you choose, don't take the view that it doesn't matter because, if you want a finish worthy of the effort you make in sanding this is where it counts.

We recommend the use of a short pile roller and the use of a brush for the very edges as the roller won't get to these without leaving sealer all over the skirting boards. Do not skimp on the sealer and remember that the manufacturers coverage figures will be reasonably accurate. You will not be able to apply too much sealer if you are using a water based seal so you need to concentrate on getting a good coverage without missing any areas. The first coat of seal will usually cause the grain in the wood to raise and the floor will feel rough to the touch. You will now need to go over the floor with a fine grade sand paper to remove the grain and to provide a key for the next coat of sealer. Not providing this key is a common cause of failure with the sealer as the top layer may show signs of peeling away. When we carry out this work we use the polishing machine with the abrasive pad and a scrad wing to remove the grain and provide a key. The process is repeated between the second and third coat as well. We use either Ronseal Trade quick cure varnish or Bonakemi floor sealers which do not leave any lingering solvent type smells and provide hard wearing low maintenance floor finishes. There are also occasions when we want an oiled finish that we use OSMO polyx oil or OSMO Colour oil which also provide a hard wearing low maintenance floor finishes. None of the finishes that we use are hazardous to health but you will need to take care when purchasing your floor finish.