VCS FLOORWORKS. everything for timber flooring

There are four different stages in the sanding process.

1        level sanding

2        coarse sanding

3        medium sanding

4        fine sanding

The first part of the sanding process is to commence the level sanding work.  This is the process that brings all of the board’s level to each other.  Note that this does not mean that the whole timber floor will come to one level.  This is a practical impossibility.  By sanding timber you bring each adjacent board to the same height as the next board.  So level sanding is smoothing the various heights of the different boards.

Level

Level sanding is done at an angle to the run of the boards.  Some sanders refer to a 45° cut.  Usually the angle is determined by going from corner to corner in the rooms that need to be sanded.  So the angle can vary quite significantly.  It has been found that it is usually better to sand a floor at an angle a little below 45° for faster results.  Usually a floor is only cut in one direction on the angle and only once, however sometimes when you run your hands over the boards after this 45° cut you find that the boards are so uneven that a further cut is needed.  In this case you cut from corner to corner in the opposite direction and thus do what we call a “wishbone” cut of the floor.  A two directional cut.  This removes a significant quantity of timber and therefore you might want to be careful about using the system.

When you use the sanding machine it has significant power and as you lower the drum gently to the floor [feathering in] you immediately feel a pull.  Do not be tempted to run or move at high speed along the floor.  You must allow the sanding machine to do its job and that means that you control the speed of the machine.  This is where the operator comes in. 

• By walking slowly and steadily behind the machine you achieve a consistent result.  Moving quickly over sections and more slowly over others creates an uneven sanding pattern. 
• Try to be consistent and move quite slowly. 
• This applies when going forwards and in reverse.

Overlap

As you sand you work your way slowly across the room overlapping the sanded work by about half.  Most sanders try to keep this consistent and where boards are relatively narrow they move over by the width of one board at a time.  This is a little difficult to see when sanding at an angle but you’ll soon get the hang of it. 

• Do not try to move the machine over by the full width of the drum. 
• Move over by half the width of the drum in each pass. 

As you work across a room at an angle you’ll find that you get quite close to the walls in front of you but that there is a reasonable distance behind you.  When you have sanded all of the area in front of you, you will then turn the machine around to take up the area where you couldn’t get to.  Don’t attempt to feather in the drum at exactly the point where you started the sanding process.  Start approximately 1 m [or one yard]  back from this and gently feather in so the by the time that you overlap the mark where you began your drum pressure is already established.  Get as close to the walls as you can on this angle cut.

If you have done this work consistently then you have done the level sanding work.  You should be able to run your hand over the floor and feel that the boards are level to each other.

Sanding machines cut better moving backwards. So sand forward and then come back on the same line. Then move the machine over half the width and then go forwards and backwards on the same line. Use this method consistently.

Overlap Direction

Because of the design of the machines with the drive belts on the left it is usually the case that a sanding machine should be used in a specific direction from right to left or left to right when it comes to overlapping.  More often than not the direction is from left to right.  However when you hire the machine you can check this point.

Angle Cutting

Note; with level sanding work it is necessary to cut at an angle.  This is unavoidable.  However if you attempt to cut the floor at 90° you’ll put in sanding marks that will be very difficult to remove.  This is why we try to work at an angle below 45° generally.  Sometimes there are areas in the home where it is impossible to do an angled cut.  For example you might have a passage that the boards run down that is only 1 m wide.  Clearly you cannot do a level sanding cut in this area.  The best that can be done is to go through the remaining three stages of the job.  However if you control the sanding machine a little more slowly down the passage you’ll probably find that the boards become quite level.

There are some timbers that are available that are extremely fibrous.  These fibrous boards sometimes respond a little differently when they are sanded on an angle. 

With particularly fibrous timber you might try dropping the angle back to between 15 and 20°.  This sometimes makes these boards sand more easily and contributes to a better overall finish.  A little experimentation does not go amiss at this stage.  So for example with Australian blue gums which can be very fibrous we would drop the angle back a little bit as we would sometimes do with other timbers of this kind.  Generally though if you use the angle that runs from corner to corner in the room you’ll have success.

Coarse sanding.

Using exactly the same grit that was used to level sand the floor it is now necessary to sand the floor in line with the boards.  Using the same sanding speed and the same approach you should gently feather in and feather out as you sand the floor down the full length of the rooms.  Take your time and only overlap by half the width of the sanded area in each sanding pass.  As you do this work you’re looking to see that all of the sanding marks at an angle that were generated in the level sanding work are removed. 

• If you feel that there are some very deep scratches in the floor then you may sand a little more slowly.  But never stop moving when sanding.

• By the time you have finished you should find that all of the 45° marks have been removed. 

Sometimes an operator will try to get too much sanding distance out of a belt.  If you have sanded a considerable area with the one sanding belt it is a good idea to change the belt and use a new one for the coarse sanding work.  This will ensure that you do not have any unsightly 45° marks in the floor by the time that you reach the coating stage.

• All of the area that has been level sanded will need to be coarse sanded using the same grit that was used for level sanding.

If simply removing old finish don’t angle sand the floor.

It could be that you’re sanding job is to remove old finish from an existing floor.  In this case you would not do level sanding but you would begin using coarse sanding.  The coarse sanding belt would be a 36 grit grade.  This is the sort of grade that will remove finish without doing too much damage to the existing timber floor.  Your aim should be to remove the finish without removing too much timber.  If you start with too coarse a belt then, while it is true that you will remove the finish easily you’ll probably introduce a number of scratches into the floor that will extend the job.  Better to go slow and steadily with a belt like a 36 grit than to aggressively attack the floor with something like a 24 grit belt.

Good belt selection is important

When removing existing finish the floor has already been level sanded.  Your aim is to keep it level while removing the finish.  Again, consistent speed with the floor sanding machine plays a key role.  You may find that the sanding belt becomes clogged relatively easily and that you have to remove it to clean with a wire brush.  This is all part of the process sometimes when you remove an existing finish. 

If you keep a zirconia belt relatively clean then it is not too hard to remove the finish.  Silicon carbide or zirconia are among the best grits for this sort of work. 

With the exception of the level sand, every other type of sanding activity discussed from this point forward applies to a floor where you a sanding all of the finish off in order to apply new product.

• When you have done this work you are ready for the edger.

Using The Edger

The edger is a very powerful machine.  It consists of an upright motor that drives a 7 inch or 178 mm diameter disk.  Sanding discs are attached to the base of the edger using a little metal fitting that screws into place.  These sit into the base so that it does not actually make contact with the floor.  The abrasive itself cuts to  just the front right hand area of the edger.  Therefore when sanding it is important that the machine is set up to cut to the front and slightly to the right.

Pitfalls

Some DIY sanders try to avoid using the edger and use a belt sander.  Typically this is been found to be a poor idea as edgers have considerably greater power & are able to cut the floor down more efficiently.  The difficulty when using a belt sander is it is quite easy to tip the machine a little as you’re sanding & this results in marks in the floor or small dips.  Thus it can take twice as long to sand the edges of a room using a belt sander than it does using an edger.  The other tool that is sometimes tried is the random orbital sander.  There are one or two quite powerful orbital sanders that have proved to be relatively successful.  However for the initial sand usually the edger is the best tool.

You will notice that when you look at the floor there are two different areas that you have to sand with the edger.  When the boards run down the room and you have to edge either side when you are sanding the boards with the run of the boards.  That is you are moving down the length of the board as you edge.  However where the boards meet the end of the room you have to sand across the board’s.  That is across the ends of the boards with the edger.  As noted earlier with the belt sander or drum sander, when you sand across the board you put marks into the board.  This has to be kept in mind when using the edge sander.  So the action for using the edger will vary a little depending on whether you are sanding down the length of a board or sanding across the ends of the boards.

Actions

When sanding down the length of the board the edger may be used in a sweeping action.  That is you may move the edger from left to right and sweep back a little from right to left if you keep the machine moving but gradually proceed to your right.  As you edge use a sweeping motion down the length of the board gradually working to your right but not being afraid to sweep back with the edger from right to left as you work.  Thus a sweeping action makes sure that you work from the wall into the work you’ve done with the belt or drum sander progressively you work from left to right until you reach the end of that wall.  Now you have the ends of the boards to sand across.  This is where your action will change.

The edger can be used in a slight rotary sanding action.  You will still work from left to right however instead of sweeping the edger you use a circular motion as you sand.  Imagine a circle with a diameter of something in the order of 200 mm.  Using the edger in a rotary sweeping action you now proceed to work along the wall.  So instead of sweeping simply from left to right, right to left, left to right and so forth back into your belt sander or drum sander area, you sweep in a circular motion. Using this method the edger will not introduce anything like as many marks as it would if you were simply to sweep across the ends of the boards.

• Never lean heavily into the edger. 
• It is an extremely powerful machine and can put very deep score marks into the floor. 
• It is designed to be used with a gentle pressure to the floor, just enough to ensure that the timber is level and sanded.

You have done the level sanding and the coarse sanding with the belt sander or drum sander and you still have two sanding grades to conduct with that machine.

Medium Sanding

Medium sanding is any grit from 60 grit through to 80 grit using the belt/drum sander.  As before the machine will be used running down the length of the boards only.  Your aim is to tie into the work that’s been done with the edger.  Don’t be too concerned if you’re using a slightly finer grit than was used on the edger to finish the edging work.  Because the edger spins at some 2500-rpm plus and the drum/belt sander sands at around 800 rpm you’ll find that they cut very differently.  The medium sanding is simply a matter of running up and down the boards to ensure that all of the area has been cut using the finer grits: 60 and 80 grit belts. 

At this stage you should be looking very closely at the floor to ensure that you have got out all of the marks that were introduced in the sanding process using the coarser belt. 

Because you’re working at a relatively gentle pressure given the fact that the belt is very fine you’d find it difficult to do a lot of damage at this stage unless that is you hold the machine in just the one spot.  Keep the machine moving doing the same feathering in and feathering out action and we explained earlier.  By the time the floor should look relatively finished and clear of dips or marks.

When you have finished all this activity you should go over the floor with a vacuum cleaner to completely remove all the dust that has been introduced.  You will then be able to see very clearly the condition of your floor.  They should be no 45° crosscut marks in the floor from the level sanding stage.  If you see any do a little more work.

The main sanding sequence is as follows.

1. 40grit Level Sand
2. 40grit Straight Sand
3. 40grit Edge Sand
4. 60grit Straight Sand
5. 80grit Straight Sand
6. 80grit Edge Sand
7. 80grit Rotary Sand

Followed by – Rotary Sequence per coating

Rotary Sanding

The rotary sander as discussed earlier is basically a glorified polisher.  They are neither extremely fast nor extremely powerful.  Their design allows you to bring the condition of the timber fiber on the floor to the same condition throughout and also to burnish the timber.  The edger sander moves at a remarkably high speed whereas the belt/drum Sander cuts at a slower speed.  If you were to apply the coating at this stage without using the rotary sander you would see a distinct difference between the edges and the main area of the floor.  This manifests itself in a different color plus you would also see a series of marks where the belt/drum sander has been.  The rotary sander is the tool that is used for fine sanding and every grit between 80 grit and 380 may be used with this machine.

Your starting sand with this machine will be a grit similar to the grit that you finished with the belt sander.  Therefore if you finish with an 80 grit belt it would be a good idea to start with an 80 grit disc.  You should work through the sanding grits jumping by no more than 100 sanding grit at a time to achieve a fully sanded floor.  So for example if you start with 80 grit you can then jump from 80 to 150, 150 to 220.

Please note that if you polish timber to a shiny finish you are highly likely to have major problems with coating adhesion. Check the container of finish that you are planning to use. Do not over sand the floor with a polisher. Whatever the manufacturer recommends is where you should finish the sanding process.

How far should I go with a rotary sander if I’m using a solvent based or oil modified finish?

Floors that are prepared for these finishes do not need to be as finally sanded as they do for waterborne finishes.  Follow the manufacturer’s recommendations.  You’ll often find that it is sufficient to sand up to a 120 grit mesh.  Therefore you would spend a considerable time with an 80-grit disc and then move to a 120grit. 

At what stage should I finish when preparing the floor for a waterborne finish?

When finishing the timber floor for one of these finishes the floor needs to be finished to a higher level.  Therefore you should anticipate finishing at something at something in the order of 150-220 grit. The manufacturer’s instructions should be followed carefully.

What is the general guideline for Polyx Oil?

Congratulations if you are looking at the OSMO Polyx range first of all. These finishes are amazing. Usually you will find that it is sufficient to finish the floor to a 100grit or 120grit. As always check the instructions on the can.

What am I looking for?

When you first run a rotary sander over the floor you will notice that there is a patchy appearance throughout the floor.  Timber fibers are sitting in different directions and have been cut differently.  Plus from board to board there is a slight difference in density depending where that board has been cut from the tree.  The rotary sander allows you to bring the floor to an even appearance across the area.  You do not want highly polished areas in one section of the floor and hardly polished areas in the other section of the floor.  You want a consistent appearance throughout.  So as you sand the floor this is what you should keep an eye on.  Look at where you are sanding and see that it is brought to an even sanded finish.

Do not over sand with the rotary machine. Two full sands with each grit should be enough if you have used the belt sander correctly.