Polishing Up On Your Floor Sanding Knowledge

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Polishing Up On Your Floor Sanding Knowledge

Polishing Up On Your Floor Sanding Knowledge

While you’re bringing in the professionals to work on your floor, you will want to know what they are doing, right? In addition, as the property owner, you should be well-versed with the different aspects that come with wood floors – especially those that are tied to your particular installation, to ensure that it receives proper care. Here, we will go over the basics of the floor sanding process, that way you won’t be out of your depth when discussing with the contractor about the job – and you can even use this to let the contractor know that you will keep them in check.


  • Skipping grits: A capital offence


For the sanding sequence, the goal is to work with progressively finer grits, flattening the floor and achieving a smooth and uniform surface that is ready to receive the new wood stain and finish, all while removing as little of the wear layer as possible. So one starts with the coarse grits – with the level depending on the particular condition of the floor, and the amount of material that needs to be removed. Many cases start out with 24 or 36 grit, but there are those where sandpaper as coarse as 12 and 16 grit are used. It then proceeds to the medium grit levels, which reach to 60, then ending with the fine 80 or 100 grit. Sure, there are extra fine grits like 120 and 150, but these typically come in during the light sanding in between floor cats. 


  • Not more than one grit should be skipped at a time. 


The initial coarse sandpaper removes the old finish and creates scratches, the medium grit comes in to remove these scratches and in turn creates shallower ones, which are then removed by the fine grit sandpaper. Starting with the coarser-grit paper then jumping to the fine grit will mean that those deep scratches have not been removed. This leaves the surface rough. As such, when the treatments are applied, there will be more product getting into the “valleys” of the cuts, and little remaining on the “peaks”, leading to uneven results. 


  • The starting grit


This will depend on the condition of the floor, the stain that will be applied, and if the flooring is composed of multiple wood species. Here, it’s recommended to first determine the end-goal and which will be the grade used for the final pass before treating and applying the finish coats, then working backwards to the coarser grits. For instance, with new untreated floors, the goal is simply to smoothen the surface. Most floor sanding jobs end with 100 or 120 grits. As mentioned, just one grit level can be skipped at a time. For example, it can follow a 40-60-100 sequence, thus skipping 50 and 80 grits, or use a 36-50-80, thus skipping 40 and 60. 

With a professional floor sanding contractor, you will be able to ensure that only the required thickness is sanded off. After all, you don’t want the wear layer being depleted prematurely, as this will cut down the number of times that the floor can be sanded and refinished in future. On the other hand, if the final pass is made with sandpaper that’s too fine, then it closes up the wood grain, leading to the wood stain and finish coats being applied having a poor adhesion to the wood. It’s an intricate balance that can be difficult to achieve without adequate skill and experience. 


  • Directions


The path of approach also weighs into the process. Two critical factors are considered here:



For the older versions of the drum sanders, a person positions the machine at the right side of the floor to be worked on, and moves towards the left. For belt sanders, the opposite happens. This difference is due to the location of the carriage wheel. For instance, split drum sanders have the carriage wheels being positioned directly behind the drum while for the belt sanders the wheel is positioned on the left side of the drum. Basically, during the sanding the direction used should enable the carriage wheels to follow the area that has already been sanded. This is to prevent overwood from being transferred to the drum, which would lead to irregularities.



You’ll usually find contractors sanding in an angle to the floor, especially with the first pass. This is a slight angle to the direction of the floorboards, typically 7° – 15°. This is to speed up the process. When working at an angle, it cuts slightly across the grain. This enables faster sanding, and also prevents aspects like waves or rolling. Since this will result in cross-grain scratches after the first cut, then the passes that follow will need one so sand straight with the grain to ensure that the scratches go along the same direction as you progress through the grit sequence. 

Wood dust is also a concern, given that it leads to respiratory problems once inhaled. From allergic reactions, to reduced lung function and exacerbating asthma, you want proper dust control measures to be put in place for the floor sanding process. Remember that the sanding dust will contain a mixture of the finish products and wood tissue being ground off the floor – and these can be toxins and carcinogens. This, coupled with issues like eye and skin irritation, makes it necessary to put the necessary safeguards in place to prevent the interior space from becoming a health hazard. 

How Do I Know My Floor Needs To Be Sanded?

While there isn’t a specific rule that covers all types of floors, there are certain signs that enable you to know that the installation is due for a sanding and refinishing. Take scratches for instance. A couple of them are nothing to worry about. However, if large sections of the floor are covered in scratches, then certainly you will want to have the floor renovated. In fact, if some of the scratches have got through the finish coats and reached the bare wood, then the sanding and refinishing should be carried out the soonest possible, since that will be an indication of the finish coats being worn out. Speaking of which, when the floor finish changes colour – such as by becoming grey over time, then the sanding should be carried out to remove the old finish and apply a fresh new one. There are also cases where one wants to change the look and feel of the floor, and the sanding will enable you to get rid of the existing treatments and apply a different wood stain that’s to your own liking. 

Polishing Up On Your Floor Sanding Knowledge

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