25 April 2026
People often picture floor sanding as one big noisy machine going up and down a room for a few hours. That part is real, but the actual process is a bit more involved, and the choices you make about the finish matter as much as the sanding itself. This post walks through what happens from the day the sander shows up to the day you can move furniture back in, plus a few notes on which finish to pick.
Step one: prep the room
Before any sanding starts, the room needs to be empty. Furniture out, curtains taken down if they hang to floor level, and any rugs or runners gone. Pictures and shelves on adjoining walls usually stay up, but anything fragile is worth moving.
The sander will then walk the floor looking for:
- Protruding nails that need punching below the surface so they do not tear an abrasive belt.
- Loose boards that need screwing or nailing down.
- Carpet staples or gripper-rod remnants from a previous floor covering.
- Sections that may need a board replaced before sanding.
Skirting boards normally stay in place. A good operator will keep the edge sander tight to the skirting without damaging the paint, although a touch-up of paint after the work is sometimes needed.
Step two: coarse sanding
The first proper pass uses a coarse abrasive, typically 24 or 36 grit. This is the heavy work. It takes off the old finish (varnish, oil, stain, or whatever is there), levels out cupping and minor unevenness, and removes deep scratches and marks.
The drum sander handles the open floor in long passes going with the grain. The edge sander follows around the perimeter and gets in close to skirting boards. Corners and tight spots around pipes are done with a small hand-held tool or scraper.
This stage produces the most dust by a wide margin. A modern dust-free system with HEPA filtration captures most of it at source, which makes a real difference if you are in the rest of the house at the time.
Step three: medium and fine sanding
The coarse pass leaves scratch marks in the timber. Those marks need to come out, which is what the medium grits are for. Typical progression goes 60 grit, then 80, sometimes 100. Each pass removes the scratch pattern from the previous grit.
The final pass for most floors is a fine grit (100 or 120) using a rotary or orbital finishing sander. This blends the edges into the main floor area and produces the smooth surface that takes the finish well.
If you skip grits or rush this stage, you can end up with a "halo" effect around the edges where the scratch pattern is different from the rest of the floor. It only really shows up after the finish goes on, by which point it is annoying to fix.
Step four: gap filling (if needed)
Sawdust from the sanding is mixed with a clear resin filler and pressed into the gaps between boards. This is optional and is more common on older floors with pronounced gaps. Worth knowing: timber moves with seasonal humidity, so filler in wide gaps can crack out over the following year or two. A modest fill of the worst gaps tends to work better than trying to seal every line.
Step five: the finish
Once the floor is sanded and vacuumed thoroughly, the finish goes on. This is where the look of the floor is decided, and the options vary quite a bit.
Water-based lacquer
The most common modern choice. Dries quickly (often walkable in a few hours, fully cured in a week or so), low odour, and stays clear without yellowing the timber. Comes in matt, satin, and gloss. Typically applied as a sealer plus two or three top coats. Good for busy households.
Oil-based lacquer
The older traditional choice. Gives a warmer, slightly amber tone to the wood, which some people prefer on oak and pine. Smells stronger during application, takes longer to dry between coats, and continues to yellow slightly with age. Less common now but still has its fans.
Hardwax oil
A penetrating finish that soaks into the wood rather than sitting on top. Gives a natural, slightly matt look. Easy to spot-repair if a section gets damaged (you can re-oil that area without re-doing the whole floor). Needs occasional maintenance with a refresher oil every few years. Popular in modern interiors and on oak.
Natural oils
Similar to hardwax oil but without the wax component. Very natural look, but needs more frequent maintenance and is less durable against spills. Better suited to bedrooms than kitchens.
Two coats is the minimum for any finish on a domestic floor. Three coats is the standard recommendation for living rooms, hallways, and anywhere with serious foot traffic. The cost difference between two and three coats is usually small relative to the longevity it adds.
How long the whole thing takes
A typical living room (around 20 to 25 square metres) takes one day to sand and apply the first coat or two. Larger areas or floors needing extra prep can run to two or three days. Drying time is the limiting factor for getting furniture back in. Water-based lacquers let you walk on the floor (in socks) within a few hours, but full cure takes about a week. Avoid putting rugs or heavy furniture back for at least seven days, and ideally two weeks, to let the finish harden properly.
Have a chat about your floor
If you want to talk through the finish options for your own floor, or you are just trying to work out whether a sand-and-varnish is the right next step, get in touch. Klenz Floor Sanding covers Dublin, Wicklow, Bray and surrounding areas. Call or WhatsApp 087 673 7497 for a free quote with no call-out charge.