Does new wood flooring HAVE to go on top of the old one?

[NoIdeasForWittyNickname]

We’re gradually renovating our 1930s doer-upper house, which was a 1980s time capsule when we bought it three years ago. All the downstairs (apart from kitchen) has plain pine wooden floorboards (revealed after removing a psychedelic carpet). It’s solid and level, but a bit meh, plus there are lots of patch repairs where the boards were cut / smashed when the central was installed and who know what else was done. So, the current idea is to get it replaced with a new engineered wood flooring.

We’ve spoken to a couple of local suppliers and fitters, and everyone is advising to fit the new floor on top of the old planks. But I’m not overly enthusiastic about the floor level going up. When I mention the idea of ripping the old floorboards and fitting the new floor directly over the joists (of course, the new boards will have to be thick enough - e.g., 20-21mm), everyone rolls their eyes and says this is not the way it’s done these days.

I appreciate there are benefits of going over the old floor (e.g., easier and faster to install, draught-proofing), but please tell me I’m not going mad thinking that laying directly over joists is still a perfectly sound method? Are the tradesmen just being too lazy and gaslighting me or am I overlooking some important technical aspects?

Sparkies dont cut walls they expect the "anyone not me" to do that, but they should have mate-rate friends
But the bigger issue will be they wont certify old wires as they did not install new back to the fusebox (who knows how many people worked on them in a old 30's house)
Op would check your insurance T&C before going near the sockets

Thanks again to everyone for the extra input and details about your own flooring projects. You have all convinced me it's better to leave the old floor in, using it as a substrate😃

@AnSolas , @MidlandCatGirl , I think you're right, I'd better looks into moving those sockets. We've been lucky enouhg to find a good electrician who actually was happy to chase the walls when we needed to move some sockets in the kitchen and install a new light switch in the hallway! That was a couple of years ago though, I hope he's still in business!

Sparkies dont cut walls
Well ours did. 🤷‍♀️

OP the engineered wood would be significantly more expensive to get in the thickness/strength that you'd need to do the floorboards out of it, which is why cheaper woods like pine are used instead and engineered wood floors are put on top, so I'm glad you're not planning on doing that now.

Of course sparkies chase out walls 😂 They might not enjoy it much, but it's part of the job!

Another skirting solution would be to use much taller skirts so the sockets end up set into the skirting (below the moulded section). This will only work/not look ridiculous if you have high ceilings.

When I replaced all my flooring a couple of years back I took up all the old floorboards as some were truly knackered. Replaced with tongue and groove P5 chipboard which is really easy to put down and comes in 1200 x 2400 sheets so quick too. Just make sure you glue it to the joists as well as then secure down. I replaced the joists whilst down there as some were rotten and also replaced the electrics and plumbing alongside insulating cavity. If you are pulling up all your flooring down to the joists I strongly suggest addressing any other issues whilst you’re down there. If you’re not afraid of a bit of sweat and elbow grease it really is a very simple job.

You asked about wear and tear on painted floorboards - ours have been great so far though we all wear slippers in the house not outside shoes. I did scratch one part moving a metal filing cabinet but I just touched up the scratch mark with paint and it’s fine - I didn’t need to repaint the whole floor or anything.

@BiscuitsandPuffin , yes the great MN has talked sense into me 😂

@SkankingWombat unfortunately just ordinary average height ceiling over here (245cm), so no grand skirting for me 😕

re bare floorboards - don't do it unless you like freezing your arse off in winter.

Not if the previous person has glued the boards down it isn't...! This is very ill advised OP.

Not sure where the OP has said the boards are already glued down? Says they pulled up a couple. Sounds like regular nailed down boards to me or did I miss something?

Thank you, @Pattygonia .

@NonmagicMike wow, sounds like a massive job! Hats off to you if you've managed to tackle it yourslef!

FYI - yes, the current floor is just plain pine planks nailed to the joists.

Consider insulation between the joists, if you take the floorboards up. Makes a big difference. If you are replacing a floor then building regs require it.
Btw I assume you meant a 25mm gap from concrete to bottom of joists not the top of joists (otherwise the joists would be 25cm thick).

@FlickFlackTrap it seems to take forever as you have to sweep it, Hoover it and then wash it. You have to be careful using water as you can't put too much on it either. Can't use a steam mop either. Just never feels properly clean. I'd rather have tiles or like my parents have really top quality laminate (can't remember what theirs is called)

In the kitchen if you open the fridge and a pot of cream falls on the floor then the grease doesn't come out for months and months and months.

In the bathroom we had a leak and the floor is just awful now.

Can you tell, I hate wood flooring 🤪

The old floorboards are part of the load bearing structure of the house. If you take them up , insulation is a really good idea, as you never get another chance. You have to put back structural boards or your floor will be weak, and they have to be nailed or screwed to the joists to stabilise them.
You could make this a presentable floor with solid oak boards but they will eventually get gappy as solid wood shrinks and swells. (A lot of people discovered this with solid oak flooring).

The engineered boards aren't usually load bearing but they are more stable due to the layers and normally laid as a floating floor ie not nailed down.

I was in a similar position, and decided to replace the Victorian pine boards with solid oak 21mm T&G. I insulated between the joists, and used hidden screws (tongue tight) and coated with hardware oil.
I was able to leave the skirting and doors in place.

5 years on it looks great and much warmer. I needed a good compound miter saw.

You suggested glueing down the new floorboards to the joists. My point was that if the person who had layed the floor you so easily lifted had been silly enough to glue it to the joists (as you have done with your new boards and recommended OP does), you would have had an absolute nightmare getting it up. Let's not inflict that on the poor bugger down the line who eventually has to lift glued down floor boards. Not only would it make it very difficult to lift, it could damage the joist below by taking chunks of the timber with it, and adds the task of cleaning up any chucks of floorboard left adhered to the joists. Nails are adequate, screws are best, but keep glue out of it!

@ForestDad (and all of you who have mentioned insulation between the boards. I'd definitely do that if we decided to remove the old pine boards. But now I'm more in favour of laying the new floor on top. I guess this in itself will reduce draughts and insulate a bit. Or would you still lift the old floor to add insulation regardless?

Re the gap void under the joists. I did mean 25cm from concrete to the top surface of joists, i.e. joists are 8cm thick and the gap underneath is 17cm. Rereading this, I appreciate this is a very clumsy description 😂 I was just trying to say there's no lethal 10-fert deep gaping hole underneath, like one of PPs has in their house.

I’m not sure that you have digested what I posted very well. I’m not suggesting you glue down floorboards. I’m suggesting that if you are going down the P5 chipboard route as I did then glue is ordinarily a part of this process unless you like a squeaky floor. There are some who won’t and who will instead go nuts with the screws to anchor it, but I’d say that glueing the tongue and groove together is the least I’d want to do if not glueing to the joists themselves. Not very easy to fix a squeaking subfloor once it all goes back down.

I’ve got my pulling up glued chipboard T-shirt. It’s a faff yes and involved a lot of swearing, but a good breaker bar and some power tools and up she came.

If you can afford the cost, time and mess I would definitely insulate under the floor. We used 4" celotex boards cut to size between the joists with odd bits of wood underneath to stop them dropping. The area under the floor is ventilated to the outside. Once you've got decent loft insulation and maybe walls, the floor being uninsulated is a big energy loss, especially with a hard floor. If you want to quantify it have a look at u/r values for various floors. From memory adding another layer of wood won't make a big difference.

Now you are contradicting yourself. You didn't recommend glueing the boards in one sentence, but you did in the following one?

I'm fairly sure I have the T-shirt too: I'm a site carpenter with 20 years of experience. I may have lifted and laid one or two floors in my time... I would always choose to 'go nuts with the screws' than glue the boards directly to the joists. I have never known another chippy to glue them either, and I've worked with a fair few. Glueing the tongues is fine. If the floor was squeaking previously, you might want to investigate why - are the joists flexing more than they should? Are the tops laying flush? Was is just the old floor was fixed with nails that can lift over time? Etc, then resolve those issues. The floor shouldn't be holding the joists in place, which is essentially what would be happening with some causes of squeaking if your solution was to just glue the boards down to eliminate the movement.
There are many reasons you may need to lift all or part of the floor in the future, and if you have glued it to the joists, you will have an absolute nightmare on your hands (and/or very angry sweary tradespeople followed by a large bill).

I didn’t recommend glueing the floorboards no, I recommended glueing the chipboard if going down that route. If you’re in the trade you will no doubt be aware that this isn’t some out there wacky suggestion dreamed up by a madman. It would appear from my experience and reading that using glue is common but it is one of those marmite situations - I.e some like you will swear blind to never use it and don’t know anyone who ever has whereas whoever did my extension 15 years ago certainly did glue it down. If you can get the whole thing to sit nicely with no squeaks using just screws then more power to you. I don’t think it’s correct however to say never use glue?

Glued and screwed is the solution I went with and if some tradey wants to curse at me in 30 years time when they have to pull it up to get at the plumbing then so be it. Maybe you’ll never be called back to a site where you’ve just screened it down as there is an annoying creak that mrs smith can’t tolerate, maybe you will. Your work your problem I guess?

Screened = screwed

Thanks @ForestDad I haven't paid attention to u/r values, I'll have a look! 🤓

Been researching the underfloor insulation a bit more closely this morning and realised that 8cm joists thickness (mentioned in my previous post) is not normal, 10cm (4in) seems to be the minimum. Pulled up those loose planks again - the joists are 10cm, just the particular one that I happened to measure yesterday has a bit chipped off the bottom edge and I didn't notice!

They’ll be 2x4’s. 95mm thick I think from memory if you want an exact answer.

950mm that should be. 95mm would be rather silly.