If you are getting wooden floors sanded and varnished

[FillyerBoots]

Before or after decorating?

Sand before and varnish afterwards.

Sand and treat the floors after the decorating is completed.

Sanding won’t mark the walls or skirting boards, and if carefully done neither will the treatment — stain and varnish or wax / varnish.

Lagler Hummel sanders are the best and dust free if you can find someone who uses one / or try and rent one if you’re DIY.

Having done both, I would never varnish a wooden floor again, I oil them.
There is no varnish in this universe that doesn't scratch like heck, no matter how good your surface prep is (and painting, though not house painting, is my job, so I do things exactly by the book). Most of them will chip and flake as well. The best varnishes are usually spirit-based, and take ages to dry, which is a pain in the neck when you do them, and a pain in the neck when you have to patch up scratches.

I got sick of all that mucking about, so I asked a Danish friend what they do in Denmark, where they have a lot of wood floors. Apparently, they oil them. I sanded all the varnish off ours and oiled them, with a good quality floor oil with plenty of tung oil in it, even the kitchen floor. Would never, ever do anything else now. Easy to keep clean, looks fantastic (not glossy, but a lovely deep finish) and patching it up if it does get scratched is just a matter of rubbing a little oil in. There's nothing to flake, so no problems there at all.

Only downside- if you have valuable rugs, you need to put a suitable (non-slip) fabric under them to keep them off the wood and be very sure to leave the oil a few days first. But you generally have to have an undermat with a varnish to stop them slipping anyway.

Whether oil or varnish, I both sand and varnish/oil after decorating, though it does mean that I have to Henry and duster up all the dust very carefully after sanding. And I make sure any spirit based gloss/eggshell/satinwood has had a good week to dry before sanding the floor. I'm a bit unorthodox in that- most people would do as setthecontrols does. But I take a top-down approach to decorating- ceilings, covings, then walls, then woodwork. Then, of course, floors. Because gravity means drips and mess (though I try to avoid them) tend to go downwards.
With this exception- with a new solid wood floor, where I'd be using a wheeled floor sander, which is aggressive and I'd be taking a lot more off in order to get a perfect level rather than just sanding to get a tooth, I'd paint the final coat on the skirtings after the floor, sanding it at the same time as the floor.

We have an engineered bamboo floor and the varnish is flaking off really badly in huge chunks. It's been down about five years and I can't even remember which company we bought it from (and I think we paid cash) so not likely we can do anything with a guarantee. I have no idea what's the best thing to do with it - I assumed sand and revarnish but I guess we'd need to take the whole layer of varnish off as it's so shit.

Sorry OP that's completely irrelevant to your question. I would have assumed we'd do it after decorating but I'm clueless about these things.

Having done both, I would never varnish a wooden floor again, I oil them.

I agree with this. Oil gives a better, longer lasting and easier to maintain finish. If applied correctly (thin coats - very easy to do) it'll dry to a lovely finish with no residue.

Regarding sanding... having been there and done that, I'd sand the floorboards before decorating, because you'll want to hover all surfaces in the room (including window, and light fittings) and wipe everything down after sanding. If you make any marks while decorating you can easily 'spot sand' them out by hand (low mess!). Then oil your floor as the last thing you do.

*Hoover!

I would sand first because you can bash into the skirting boards etc - & then cover the floor with clothes but I agree with oil rather than varnish .

There is no varnish in this universe that doesn't scratch like heck

Dulux diamond glaze won’t. I did two different floors with it and it survived furniture being dragged about on it etc no problems. Dries in about half hour too. Matt/satin finish, almost like it’s not there.

Costs a fortune though.

My floorboards are all exposed down stairs and I strongly disagree with the poster who would only oil. I’d never do that, it needs constant maintenance and marks so easily. If the poster had issue with varnish it’s due to poor application

Mine were done about six years ago, the workmen applied four thin coats of industrial varnish, there is still not a scratch anywhere even though there are dogs, heels etc on it often. Previously it was oiled and everything marked it.

We have Bona floor varnish in ultra matt. It’s really hard wearing, did 8 years in our previous house with no marks or flaking. We have 100 m^2 of parquet here on the ground floor, sanded with a Hummel system and sealed with Bona. It’s brilliant. It was the last thing we did to the house after everything else was finished.

You shouldn't be getting close enough to the skirting boards with the drum sander to bash them -- especially if a professional is doing it. The edge sander will take care of the skirting.

A great and natural finishing product is Osmo Hard Wax Oil. It's available in natural and different coloured stains as well as matt / glossy . For best results apply it with a natural bristle broom brush. It's very hardwearing.

You can also overcoat hard wax oils at a later date unlike polyurethane vanishes, which require a full re-sand -- which isn't great for floorboards.

Duluth matt varnish (Diamond) is absolutely fantastic. The key is good prep and careful application. Imo it is far more hard wearing than oil and looks much better.

I was only speaking about this with a decorator today - he recommended sanding before and varnishing after decorating as the ideal sequencing.

As an aside, for anyone who uses Danish / linseed oil or similar staining oil on wood, be careful of where you put your rags afterward (put them outside, contained, soaked in water): m.youtube.com/watch?v=9yq6VW-c2Ts

I had a near miss with this - a used rag spontaneously started burning in my closet and luckily I noticed before it caused any damage - and had never heard of this as a thing! So I spread the word whenever oiling wood is mentioned!

@Lonelycrab

There is no varnish in this universe that doesn't scratch like heck

Dulux diamond glaze won’t. I did two different floors with it and it survived furniture being dragged about on it etc no problems. Dries in about half hour too. Matt/satin finish, almost like it’s not there.

Costs a fortune though.

Been there, done that. I'm generally a Dulux fan, so I avoided mentioning the name, but that stuff scratched like heck off two different wood floors and flaked off. And yes, I did my surface prep properly, honest. Sanded it right back from the previous varnish and everything. But that was a long time ago. Maybe it's better now.

I'd still oil. I prefer the look of it now I have tried it.

@Bluntness100

My floorboards are all exposed down stairs and I strongly disagree with the poster who would only oil. I’d never do that, it needs constant maintenance and marks so easily. If the poster had issue with varnish it’s due to poor application

Mine were done about six years ago, the workmen applied four thin coats of industrial varnish, there is still not a scratch anywhere even though there are dogs, heels etc on it often. Previously it was oiled and everything marked it.

I had oil and never touched it for years in the main rooms, still looked fantastic. In the kitchen I got a scratch or two when some grit got under a chair leg. Took about 2 minutes to rub some oil in, job done. It doesn't need maintenance if you apply it right. And I did apply the varnish properly, and prepared the surface properly according to the manufacturers' instructions in all cases- to the letter. Painting is my job.

I wax my floors which I find extremely easy care and much prefer the appearance to varnish.

We've got original wooden flooring in our home, we sanded and varnished... hated it. So removed varnish and treated with hard wax oil, its so much nicer.