Adhesive on timber can be a renovator’s nightmare, especially if the adhesive is old carpet glue stuck to a wooden floor you want to revive. Whatever method you use, it’s a messy and time-consuming job, but the secret is to use the right products and equipment, otherwise it will take even longer. If you want to remove adhesive tape and still retain the existing finish (varnish, polyurethane and so on), use a commercial adhesive remover. To remove old floor-covering adhesive (from carpets and cork tiles for example) the easiest solvent to use is paint stripper, as it rips through adhesive and softens it up in no time.
Scrape off as much adhesive as possible, using a paint scraper. The most effective scrapers are those with sharp replaceable blades. Drag the scraper towards you rather than pushing it away from you to prevent gouging or splintering the wood. For large chunks of adhesive such as old carpet glue on floorboards, with bits of underlay or cork tiles still stuck to it, use a square-ended spade, pushing into the edge of the adhesive at a shallow angle (just above horizontal) so you get in between the adhesive and the wood. Be careful not to damage the wood under the adhesive by gouging.
Apply a proprietary adhesive remover to small areas where you want to retain the existing finish. Follow manufacturer’s instructions for how long to leave on, how to remove and how to neutralise (usually with soap and water).
Apply paint stripper to the adhesive in situations where the existing finish will be replaced. For example, if you are renovating an old floor that has old carpet glue or cork-tile adhesive attached, you will need to refinish the surface as the adhesive will probably have damaged the finish. Work on a small area at a time, applying stripper with a paint brush, until you get used to the amount of stripper required and the time it takes to soften the adhesive. The stripper will work faster on adhesive than on layers of paint so it may not need to be left on as long or applied as thickly.
Scrape off stripper and old adhesive with a paint scraper or wide putty knife when the adhesive is soft. Wipe "gunk" onto old newspaper. Before the residue dries, wipe the timber with a neutraliser (follow manufacturer’s instructions, but this is usually soapy water). Sand lightly with fine sandpaper, sanding with the grain of the wood.
When using the paint stripper, test a small piece first to see how long it takes to work. To make the stripper go further, scrape the stripper and old adhesive off along the wood instead of removing it and reuse it on the next stretch of timber. You can keep doing this until the stripper becomes a thick paste. For very large areas, such as a large floor, use a drum sander or a sturdy belt sander with coarse sandpaper (40 to 60 grit). The sandpaper will clog up more quickly so be prepared to change the sanding belt frequently. Start by sanding diagonally across the floor to remove uneven bits, and finish by sanding with the grain. Then sand with a medium sandpaper with the grain, and finish with a fine sandpaper with the grain. Adhesive can also be removed with a heat gun. Be careful not to scorch the wood, and always scrape up the residue as you go along or it will harden and be difficult to remove.
Wear safety equipment when working with power tools such as a sander, and with paint stripper: safety goggles, rubber gloves, sturdy footwear, ear protectors, respirator (to protect against sanding dust and for chemical fumes) and clothing to protect arms and legs from splashes of stripper. If paint stripper gets on your skin you may not notice it at the time but it sticks and will start to burn. Wash off immediately with plenty of soap and water.