Carpentry Guides Flooring

Sanding a Wood Floor

Having sanded wooden floors can make a big difference to the look and appeal of your house. Take a look underneath your carpets, particularly if you live in an older house, and you might be surprised at the quality of the boards underneath. With a bit of time and effort, you can transform even tired and dirty floorboards into an attractive feature.

Floor Sanding is a fairly easy DIY task as long as you take your time and have the right equipment. It is, however, dirty, dusty and noisy, so make sure that you have adequate ventilation and that you take the possible disruption into account.

Preparing and Repairing Floorboards

Almost any wooden floor which has not been maintained for years will need a bit of tender loving care before you can sand it and expose it to the world. There is little point sanding and sealing a floor which isn’t in the best possible condition to start with.

The first thing you should do is check the general condition of the floorboards. Look for signs of dry or wet rot and treat this if found. Also look for signs of woodworm in the boards. If you see the tell-tale holes in the surface of the wood, you can be sure that there will be more underneath the surface. Luckily, in the UK woodworm is not such a huge problem as it is in other countries. That said, if you find signs of this wood-boring beetle, treat them before you start sanding. You can read more about Treating Woodworm here.

If any of your boards are warped or split, you need to replace them if you want a good finish when the floor is sanded. If possible, find second-hand boards which match your existing boards. Second hand and reclaimed floorboards can often be found at your local architectural salvage yard or even at a recycling centre. If you can’t find reclaimed boards to match, buy new boards and stain them to match the surrounding boards as closely as possible.

Finally, replace any missing nails and use a hammer and punch to drive all of the nail heads below the surface of the wood. The sanding process will remove at least a couple of millimetres from the surface of the floorboards, so aim to sink the nail heads by around 3mm.

Filling Gaps Between Floorboards

If you are very lucky, your floorboards will be perfectly laid, with no gaps between them. For everyone else, the next job should be filling the gaps that have appeared between the boards. Over time, wooden floorboards expand, shrink, move and warp to reveal gaps. These gaps can be left as they are if not too large, but if you want a perfect finish, filling the gaps is the only way to go.

sanding wood floor - filling gapsThe most labour intensive solution is to pull up all of the boards and completely re-lay them. This is not too difficult, but it is time-consuming, even if it should give you the best final result. Once all of the boards have been lifted and butted up close to each other, the resulting gap can be filled with a new board (or trimmed board). Bear in mind that you might need to remove skirting boards as well as the floorboards to relay your floor completely.

A second option is to fill the gaps between the floorboards with strips of wood. You can buy thin strips (or laths) of wood from most DIY stores and timber merchants. These can then be planed to the exact fit and glued into place using PVA glue. Apply the glue to the gap, tap the strip of wood down into the gap and then plane off any excess. If you choose wood which matches your floorboards, you should hardly be able to notice where the gaps have been filled. This method is not really suitable if there are gaps between every board. If that is the case, consider the method above.

Choosing a Sanding Machine

floor-sanderUnless you have arms like Popeye, floor sanding can only really be attempted using an industrial sanding machine. These can be hired from any good tool hire shop and should come with three grades of abrasive paper: Coarse to level the boards, Medium to smooth them and Fine to provide the finish. For any room larger than about 3 metres square, an upright drum sander will be needed. You also need to consider hiring a smaller rotary sander to sand the edges and corners of the room. If sanding the floorboards in a small room, a rotary sander should be fine for the whole floor.

Another useful tool is the Hook Scraper. This handheld tool is great for removing paint spots on  areas of the floor inaccessible to the drum or rotary sander.

Fitting Abrasive Paper

Depending on the model of the drum sander you hire, the exact method of attaching the sheet of abrasive paper might vary slightly. In most cases, the paper is wrapped around the drum, pulled tight and then secured with a screw-down metal bar. The abrasive paper for rotary sanders is circular and attached using a central screw or nut.

Never attempt to fit new abrasive paper when the sander is plugged in, and always make sure that the sheet is pulled tight against the drum before starting to sand. If the paper is not tight it could slip from the metal clamp and will be torn to pieces.

[stextbox id=”info”]Sanding Safety – Always wear goggles and a dust mask when floor sanding. The process creates a lot of dust, so it is a good idea to keep internal doors closed and a window open when sanding. [/stextbox]

Sanding the Floor

Sanding a floor properly requires you to switch between the drum and the rotary sander several times. Trying to do all of the drum sanding first and then all of the rotary sanding will result in a poor finish.

Drum Sander – Before switching on the drum sander, tilt it back so that the abrasive drum is completely off the floor. Switch the machine on and slowly lower the drum flat onto the floor. Don’t hold the sander in one position for more than a couple of seconds or it will sand a deep groove into the floorboards. Let the sander move forward on its own (you won’t need to push it) whilst you control the direction and keep it at a smooth a steady pace.

With the coarse paper fitted, and starting from the corner of the room, move across the room diagonally. When you reach the end of the first run, tilt the sander back to lift the abrasive paper off the floor and turn around. Line up next to the first strip, overlapping slightly, and lower the drum back onto the floor to sand back across the room. Repeat this until the whole floor (excluding the edges) has been sanded and then sweep the dust from the floor. Repeat the whole process once again, but starting in another corner so that you are sanding across the other diagonal of the room. This process will flatten and even up the whole floor.

Rotary Sander – Using the coarse paper disc, sand all around the edge of the room using the rotary sander. Even using the smaller rotary sander, you won’t be able to get right up to the skirting boards or into the corners. Get as close as you can and finish the very edge with a hand-held sander if needed. When using the rotary sander, don’t hold it in one place for long and don’t push down on it. Each time you switch the abrasive paper on the drum sander, also switch the paper on the rotary sander.

Drum Sander – With the drum sander unplugged, change to the Medium abrasive paper. Once again starting in a corner, sand the whole floor again, but this time follow the direction of the floorboards rather than working diagonally. One pass over the whole floor should be enough.

Rotary Sander – Repeat the process of sanding the edges with the rotary sander, using the Medium abrasive paper.

Drum Sander – Finally, switch to the Fine abrasive paper and repeat the same process as with the Medium paper. Take extra care with this final pass with the drum sander as this will give you the finished surface.

Rotary Sander – Sand the edges using the Fine abrasive paper fitted to the rotary sander. Finish the very edge of the room using a hand-held sander as before.

Finally, sweep the whole room to remove the sawdust and then wipe the boards with a cloth dampened with white spirit. This will remove any grease and prepare the floor for finishing with varnish.