Sanding Lines And The Integrity Of The Floor Finish

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Sanding Lines And The Integrity Of The Floor Finish

Sanding Lines And The Integrity Of The Floor Finish

The floor sanding and refinishing process is an art. With so many factors coming together, you need to get it right every step of the way to wind up with the results you desire. The sanding stage is the first step, preparing the surface for the treatments that are to follow. One of the common complaints from those going the DIY route or hiring rookie contracts is that the machines used cause side-cutting on the floor, or leave behind lines on the surface. What causes this? Let’s delve deeper into it. 

10 Causes Of Sanding Lines And How To Deal With Them


  • Wrong sander setup


Here, the sander has not been set to cut flat, which results in the side-cutting. There will be lines on the wood on one of the sides of the path that is being worked on. This is avoided by taking time to level the sander before starting the task.


  • Excessive drum pressure


The different types of wood need to be worked on with different pressures. For instance, while hardwoods like maple, oak and peach can handle high loads, the softer species like pine, fir and cedar should be sanded with less pressure. Too much pressure results in vertical lines being formed. Here, one needs to check the pressure being exerted by the machine and adjust it accordingly depending on the particular type of wood floor being worked on. 


  • Sanding speed


The pace of manoeuvring the sanding machine over the floor also weighs in. When you move the sander too slowly it will cause lines to be formed on both edges of the floor sanding path being followed. The pace should be adjusted based on the situation at hand. After all, when you move too fast there will be sections that won’t be properly sanded, resulting in patches of the old finish being left behind – which is also another common occurrence during the DIY floor sanding. Note that the patches will prevent the new floor treatments being applied from bonding well with the bare wood, which will thus ruin the quality of the results. 


  • Cut sandpaper


As you move the sandpaper over the surface of the floor, some items like staples or nail heads can damage it, affecting the uniformity with the rest of the unaffected sections of the sandpaper. For instance, sanding over the nails will remove or dull the mineral that is on the sandpaper, and this will lead to a streak being formed on the surface which will be noticeably less sanded compared to the adjacent sections.

When nailheads simply damage the sandpaper, you can consider yourself lucky. The exposed nail heads can actually cut right through the sandpaper and gouge the drum itself. Here, the functionality of the drum will be compromised, and you’ll need to acquire a new one. 


  • Improper setup of the abrasive


This looks at how the sandpaper has been secured. If it shifts on the top roller, that back and forth movement will cause the paper tracking to be inconsistent, creating vertical lines. Usually, one simply needs to adjust the paper tracking and centre the sandpaper on the drum. The sandpaper quality should also be checked. In some instances, the top roller may be damaged and will need repairs to be done. 


  • Unbevelled edges


This is for the drum, and it is usually common with the new units. Here, one simply needs to bevel the edges. Using sandpaper on the edges and rounding them off will usually suffice. 


  • Delamination of the drum’s rubber


There are situations where the rubber on the drum’s edge delaminates. The centrifugal force experienced during the sanding process may also result in the “growing” of the rubber, where it moves away from the drum’s centre. This will lead to vertical lines being formed on the floor. In such a situation, you will need to replace the drum itself. 



The vertical lines on the sanded floor can be caused by wheel issues. For instance, the steel wheels on drum sanders may be worn out, such that the crown is depleted. This will be a direct threat to the wood, especially with the heavy nature of the machine. The softwood flooring definitely will be at a greater risk. 

It can also be a case of bent track brackets. Here, the machine cuts the surface flat, but one of the wheels is angled, causing lines to form. This is why it is imperative to check the conditions of the wheels before proceeding with the floor sanding process, and replacing them if necessary. 



Debris like adhesive material and filler mixtures on the drum and top roller will cause bulges in the sandpaper. As you sand the floor, vertical lines are formed. To prevent this, one needs to ensure that the sander is properly maintained, which includes clearing out the debris from the unit. 



Here, the person carrying out the sanding makes mistakes like using one path for the forward pass, and a different one for the back pass. They should follow the same path. Failing to properly overlap the cut patterns as well can lead to lines being formed on the floor, as well as applying excessive pressure on the feathering handle. Here, there may also be broken lines being formed, which also mess up the quality of the results.

Skip The Risks – Turn To The Pros

As you can see, the floor sanding involves lots of balancing acts. From ensuring that the machinery has been properly set up, to the execution itself which will be greatly determined by the skill-level of the personnel handling the job, you want to ensure that it is properly done. To avoid the hassle involved, and protect the integrity of your floor, bring in the professional floor sanding crew. Here, you want to deal with a company that is well-resourced for the project, one that has made a name for itself in the industry, and with a verifiable track record, complete with reviews and testimonials to boot. 

Sanding Lines And The Integrity Of The Floor Finish

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