It is generally recommended to lightly sand a wooden surface before re-varnishing to ensure proper adhesion and a smooth finish. Sanding helps remove any dirt, grime, or imperfections that may have developed on the surface over time and creates a slightly rough texture, allowing the new varnish to adhere better.
However, if your wooden front door is in good condition, and the existing varnish is still intact without any visible wear or damage, you may be able to skip sanding and proceed with the re-varnishing process directly. Here are some steps to follow:
Clean the door: Thoroughly clean the door's surface with a mild detergent and water to remove any dirt, dust, or oils. Rinse it well and let it dry completely.
Inspect the door: Check the door for any areas with peeling, chipping, or damaged varnish. If you find any such spots, you should consider sanding those specific areas lightly to ensure a smooth and even finish.
Test a small area: Before proceeding with the full re-varnishing, test a small, inconspicuous area on the door to ensure the new varnish adheres properly. Apply a thin coat of varnish, following the product's instructions, and see how it dries and adheres.
Apply the new varnish: If the test area looks good and adheres well, you can proceed with re-varnishing the entire door. Use a high-quality varnish suitable for exterior wood and apply it following the manufacturer's instructions.
Follow proper drying and curing times: Allow the varnish to dry and cure according to the manufacturer's recommendations. This will ensure the varnish fully sets and provides optimal protection.
Keep in mind that skipping the sanding step might result in less optimal adhesion and longevity compared to a properly sanded surface. However, if the existing varnish is still in good condition and you apply the new varnish carefully, you should be able to maintain the door's appearance and protection without significant issues.