Floor Sanding 101: A Walk Through The Basics

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Floor Sanding 101: A Walk Through The Basics

Floor Sanding 101: A Walk Through The Basics

Floors are sanded for different reasons. These range from repairing damage that has occurred as a result of day-to-day usage, situations where you want to change the colour of the flooring- removing the existing finish and applying new wood stains that provide the new décor that you want to obtain, to renovation works, where you want to revitalise the floor- removing the old finish and applying a fresh one. You may be dealing with water damage, stains that have soaked through the finish and into the upper sections of the wood- it varies from one establishment to the next. The common ground is that the floor sanding gives your installation a new beginning.  

Solid wood floors can be sanded several times over their life, while for the engineered wood flooring this is usually limited to 2 to 3 times. Note that the sanding process eats into the wood itself, hence there will be a limit to how many times it can be carried out. For the solid wood, since the structure is uniform through the material, one gets more leeway. For the engineered wood, the number of times will be determined by the thickness of the veneer. Sanding too much into the wood will decrease the life of the installation, and leave little room for future repairs. Hiring a professional to carry out the task is key, as the contractor will be responsible for ensuring that the flooring is protected, and the sanding is carried out safely.  As the property owner, you also need to understand different aspects that go into the job. That way you won’t be flying in blind. Here is a look at common issues that come with the floor sanding job:

The sanding sequence

The general approach is to start out with coarse-grit sandpaper, and then progressively move to the finer abrasives. The initial grit levels can range from 30 to 40, though there are situations that call for as low as 12-grit.  Floors are different, and the particular condition of your installation will determine the grit that will be started with. A thorough inspection is needed before the process begins- even for the new floor installations. 

Why is the sanding sequence important? The goal is to abrade as little of the wear layer as possible with each pass, until the surface becomes smooth and ready for a new finish to be applied. When one goes skipping grits in the process, a problem is created. The first grit will leave scratches that will be too deep for the subsequent grit used to remove, as it will be too fine. This causes the surface to be uneven, and the finishing process that will follow will result in uneven wood staining and varnishing. What’s more, skipping the grits causes excessive wearing down in the heavily trafficked areas. It is therefore not advisable to skip more than one grit level in the sequence. Hence, one moves from coarse-grit paper, to medium-grit paper which will remove the scratches formed with the first cut, and leave shallower scratches. These will then be removed by the fine-grit sandpaper to follow.

Floor sanding machines used

Different kinds of equipment are involved in the sanding process. These range from the drum sanders for the open floor space, to the edgers for dealing with the edges, plus sections like hallways with the floorboards running across the width of the hall where it’s too shallow to use the drum. The professional floor sanding contractors who have years of experience will be able to ensure that there are smooth cut transitions obtained at the wall lines. Handling the machinery itself takes practice- with even aspects like smooth start and finishing being required- especially since it will be in motion. A common DIY mistake made is starting the sander when its drum is in contact with the floor when turning it on. This will form divot marks. Stopping for a brief moment while it is still in motion creates a deep trench on the surface- which is called a ‘stop mark’. Sanding is done safely when the sander is in motion in a straight line forward or backwards- not when turning or changing directions. 

Speaking of directions, this is also determined by the type of the machine, and the wood grain of the installation being worked on. For instance, with belt sanders, one starts on the left and moves to the right, because of the location of the carriage wheel on the unit. The wheels of the split drum machines are positioned directly behind the drum. Basically, when the floor is being sanded, the carriage wheels should follow behind on the section that has already been sanded, to avoid transferring over wood from the boards to the drum, as it would lead to irregularities with the sanding. Why is a light angle usually used when making the initial pass with the sander? Working at an angle to the direction of the floorboards- such as 7-15 degrees, speeds up the process. This is referred to as cutting across the grain, which also has the welcome benefit of preventing rolling or waves being formed on the surface.

Completing the sanding process

Floor sanding, in essence, is like art- where the contractor will have control over the final outcome. For this to be delivered to the client’s needs, a comprehensive understanding of the client’s expectations is required. This includes the treatment process to follow, whether there will be a wood stain applied, and the finish to be used- plus factors such as the floor being a combination of different wood species.  Usually, the sanding is carried out to the fine grits of 80 and 100, after which the surface will be ready for sanding. However, there are situations where grits finer than 120 will be required. Going too fine with the git can end up closing the wood grain, which would negatively affect the adhesion of the finish coats to be applied, and also make the wood stain appear to be lighter. Ensuring that the floor sanding is done by an experienced professional will enable your goals to be met.

 Floor Sanding 101: A Walk Through The Basics

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