Replacing upstairs floorboards...best way?

[Chlad]

After quite a bit of work done in the house it has become apparent that the current decades-old floorboards upstairs need to be replaced. I thought that at the same time I might as well do something to tackle the insulation and noise transmission issues (as much as I can).

Would I be able to use something like Thermafleece Cosywool in between the joists? If so does it need to be installed on a memberane? We are talking about first floor joists and not groundfloor.

Then my thoughts were: 6mm plywood on top of the joists, thin underlay on top of the plywood and tongue and groove redwood floorboards. Does this sound right?

When I fit the redwood floorboards I'm not planing to glue between tongue and groove. I will leave a half inch gap all around the room though (which will be covered by the skirting boards). Do I need to screw the floorboards to the joists? Using screws like these https://www.screwfix.com/p/spax-tx-coun ... 0wodFrwLIQ

Or will the screws affect the woods ability to expand and contract?

 

[Jacob]

After quite a bit of work done in the house it has become apparent that the current decades-old floorboards upstairs need to be replaced.

Are you sure? this is very unusual unless the floor has been severely damaged in some way

I thought that at the same time I might as well do something to tackle the insulation and noise transmission issues (as much as I can).

The ceiling below is more relevant than the floor. Double plaster board plus a layer of sand is very effective

Would I be able to use something like Thermafleece Cosywool in between the joists? If so does it need to be installed on a memberane?

Yes for heat insulation but not for sound reduction.No need for membrane

Then my thoughts were: 6mm plywood on top of the joists, thin underlay on top of the plywood and tongue and groove redwood floorboards. Does this sound right?

No. Just nail the boards straight to the joists.

When I fit the redwood floorboards I'm not planing to glue between tongue and groove. I will leave a half inch gap all around the room though (which will be covered by the skirting boards). Do I need to screw the floorboards to the joists?

No, use lost head nails. Quicker neater cheaper and less conspicuous. Don't glue anything!
No need for wide gap at the edges - movement takes place between each board and with new wood is always shrinkage and not accumulative. Advisable to buy the boards well in advance and store them in the house to accelerate drying. Or lay them without nails, cover with Protec or similar and only nail/cramp them up after 6 months or longer

 

[MikeG.]

Jacob has that almost spot on, with the exception of the sound insulation thing. He is quite right about double tacking the ceiling, or pugging it, but wrong to say that mineral wool/ fibreglass doesn't have a role in the reduction of sound transmission. It helps reduce airborne sound transmission, and when you consider that most sound emanating from, say, a bathroom over your head, is airborne, then filling the void with insulation is actually quite effective and important. I do it as a matter of routine in all projects I get involved with, and including my own houses. You absolutely do not need any sort of membrane. In fact, it would do more harm than good.

I too would question the need for removing a floor and replacing it. There is very little I can think of that would lead to that being the best course of action. If it had become woodwormy and rotten then maybe, but then you should be fixing your ventilation and heating systems before you fix the floor.

 

[Stormer1940]

Regarding insulation, Wickes have a soundproofing insulation on offer at the moment. Buy 3 or more and get them at £20 per pack normally £25.00 each.

https://www.wickes.co.uk/Rockwool-Sound ... m/p/148842

 

[Woody2Shoes]

While insulation designed for predominantly thermal benefits will reduce the transmission of sound, it generally isn't as dense as insulation which is primarily designed to reduce the transmission of sound. When it comes to sound insulation:

- higher density is good e.g. http://www.noisestopsystems.co.uk/acoustic-insulation ;
- air gaps are not your friend - this type of stuff helps to fill them - Everbuild AC50C4 Acoustic Sealant and Adhesive ;
- mechanical "decoupling" of structural elements also helps e.g. laying this type of stuff along the top of the joists will reduce sound transmission via the joists https://www.hushacoustics.co.uk/sound-c ... st-strips/ this stuff also reduces risk of squeaky floorboards

http://www.noisestopsystems.co.uk/how-t ... oof-floors

Cheers, W2S

 

[Jacob]

....and when you consider that most sound emanating from, say, a bathroom over your head, is airborne, then filling the void with insulation is actually quite effective and important. .....

noise nuisance from a room above is invariably from impact on the floor, (or impact on things standing on the floor e.g. sound of bath filling, bog flushing) with airborne very secondary (unless people are tip-toeing about about but playing very loud music etc).
Vice versa for sound from a room below. Insulation will help a bit either way, but mass is the big issue.

 

[MikeG.]

OK, let's be blunt. It's the airborne sound of people's bodily functions which we're talking about here, and the insulation helps with that. So does meticulous attention to gap filling. Without separated layers (eg de-coupled ceiling on dampers) you aren't going to affect the the transmission of impact sound, but who cares, so long as dinner guests can't hear the sound of someone on the loo above their heads.

 

[Chlad]

Thank you very much for the replies guys. I'll clarify some of the points raised.
The floorboards in 2 of the rooms, landing and bathroom need to be replaced mainly because it appears that through the years they have been hacked into and chopped to bits whenever someone has done some work under them. I discovered this after I lifted all the carpets. We also had a recent extension built which involved knocking down walls and putting beams in and the builder made an even greater mess. The rooms look like a patchwork quilt of various bit of floorboards, some old and some new, some white and some red, some screwed and some nailed, peppered with staples, warped, some tongue and grove and some not, uneven gaps, warped boards and so on. Considering that I dont intend to use carpets again I have no choice but to replace them.

At my local timber merchants I was given the choice of 5" white pine or 6" redwood so I thought redwood would be better.

The reason why I was thinking of using screws rather than nails was so that if in the future I needed to lift the boards to carry out work then it will be less likely to damage them.

My thinking behind wanting to use 6mm ply and wooden flooring underlay underneath the boards was that this might help with creating a further barrier and help to a degree with sound insulation. However if this wont have an impact then I could get the acoustic insulation strips which are stapled on top of the joists and then lay the floorboards on top of that? Or i can lay a sheet of 3mm rubber like this https://www.slip-not.co.uk/productdetai ... near-Meter on top of the joists and then float the tongue and groove redwood on top of that?

The option of doing anything to the ceiling is not possible because it would cause havoc and be quite expensive. We already live in the house with young kids so you can see the headaches and difficulties that would create.

In terms of noise both Jacob and Mike are right. When i am downstairs I can hear the sound of water/fluids impacting on the bath or toilet. And I can also hear the chatter of my kids or the music my son plays (which is actually not loud). The airborne noise is the one which is heard the most though in my case. Especially considering that the airborne noise is also heard on both directions (i.e. you can also hear the sounds from downstairs such as tv when you are upstairs).

 

[Phil Pascoe]

I assume you're to varnish or finish the floor in some way, otherwise you'd be better off replacing the whole floor with chipboard - cheaper, quicker and easier. Better heat and noise insulation (no gaps), less dust movement and more even carpet wear.

 

[Chlad]

Phil, yes, that is the intention. I dont want to go back to using carpets and will only use rugs so will have to varnish the floor.

 

[Phil Pascoe]

Thinking about it - varnished (water based P.U.) chipboard floors are very common in NZ - they don't look bad at all.

 

[porker]

Personally I wouldn't nail them but use screws. Nails in my experience have a tenancy to 'give' after some time and result in a squeaky floorboard. I use tongue-tite floorboard screws as they have small heads if the boards are exposed. The other advantage being that you can easily lift the boards later if you need to. The other issue I have come across is that 'off the shelf' floorboards are often thinner than old boards. There are ways around this of course but something to be aware of. For bathrooms I tend to take it all out and replace with chipboard.

 

[Chlad]

Regarding insulation, Wickes have a soundproofing insulation on offer at the moment. Buy 3 or more and get them at £20 per pack normally £25.00 each.

https://www.wickes.co.uk/Rockwool-Sound ... m/p/148842

Thank you for the heads up. Checked them out but their density is only 45kg/m3. So looked for other Rockwool products and found this one with 100 kg/m3 which sounds better https://www.insulationexpress.co.uk/roc ... tion-slabs

 

[Eric The Viking]

Couple of thoughts:

Speaking as an ex-professional sound engineer (and properly trained, to boot), for noise above or (occasionally) from underneath, structural transmission is by far the worst problem in older buildings. The entire floor can act as a drum skin - resonating with whatever is creating the sound.

Because floor is usually very well coupled to ceiling below by joists, anything you put in the inter-floor gap will not be very effective against percussive sounds, although as already said it *will* have an effect regarding airborne ones. The trouble is that's mostly not the sound that carries vertically in the first place.

Jacob is spot-on in that regard.

The best approach is to kill the sound upstairs at source - shoot the children! Seriously, thick underlay and good carpet works well. I put laminate flooring into one of the children's rooms - really dumb idea at many levels, and noisy underneath, even though there is a layer of the official sound-deadening underlay. So my preferred solution is

Carpet
Underlay
5mm ply
Floorboards

Ply fixed by single-start screws and boards either by screws or nails.

Note that the fast screws are generally your enemy for this: floors tend to move, and the self-cutting or double-start threads tend to work loose. That means holes in carpets! DAMHIKT!

Hardboard is cheaper than ply, but it doesn't work as well, responds poorly to liquid spills (it swells up), and over time sheds a lot of fibers, meaning it can work loose and create a lot of dust between it and the boards - in my opinion unsuitable for heavy-use areas.

As a DIY person, I am careful to get a room thoroughly finished, before putting plywood down, as it's a horrible job lifting it before the floorboards. You must lay the sheets across the boards, obviously, so you end up taking up a lot more floor than you'd like.

So do your downstairs lighting first!!!

Also write on the floor, ideally both on the ply and the boards below, where the services run. In particular notched pipe runs and power cables. You shouldn't notch for cables, but sometimes it's impractical to redo poor work of the past.

Finally, house wiring fires are rare nowadays, but most cable manufacturers specify different current loads for cables that are air cooled against those buried in solid walls or otherwise heat-insulated. If you do put stuff between the floors, check that you're not causing wiring issues by so doing.

 

[Chlad]

Eric thank you very much for your input. Blimey, nothing is as simple as you first think. It sounds like in my attempts to improve the situation I might be risking to set the house on fire. So I have abandoned the thought of using anythng between the joists. I also dont want to use any carpets either and "fortifying" the ceiling below would be too expensive as well.

So the only option I have left is using something between the flooring and the joists. Now I am aware that rubber is usually quite a good isolator so how about this option:

acoustic isolation strip glued on the joists
5-6mm ply on top and screwed to the joists
a fullt layer of 5mm thick rubber mat like this https://www.slip-not.co.uk/productdetai ... near-Meter
Redwood floorboards tongue and groove and floated on top

 

[Eric The Viking]

Bluntly, I think that is pretty much a total waste of effort, and very expensive, too.

You will "take the curse off" footfalls above (reduce the higher frequency component), probably, but 9/10ths of the noise will still get through.

It's simple: floorboards are a noisy surface to start with (and they resonate). Chairs beds and other furniture moving across them, shoes with hard soles, etc. will all make noise that transmits.

Assuming your insulation is elastic (it needs to be), you will have great difficulty getting the floor to behave properly, as basically you're not securing the boards as they are intended to be fixed. On the other hand, if you do secure them tightly, you're compressing the rubber, which defeats the object.

I'm sorry you don't like the solution, but bare, hard floors are always noisy. Even the Victorians had central carpets, often with compressed horsehair/felt underlay.

Incidentally, a traditional lath and plaster ceiling will be a lot quieter than plasterboard, as long as it's in good condition. I've been in new build (years ago, admittedly), where you could even hear the room acoustic above from the room below. So if someone was, say, hammering wood in the bare room above being worked on, you could hear the "echo" (in the room above) from downstairs. That's with chipboard instead of proper wood (chipboard, incidentally is very good for sound insulation, as long as it's thick enough, but it's not exactly decorative!).

At the end of the day, it's your place, and your choices of decoration. The most cost effective approach is as I originally described, and it also probably works the best too.

You can't stop all noise anyway - it's a balance of cost versus effectiveness. I know one commercial (formerly BBC) studio which has acoustically-isolated editing rooms above the main studio. They're built as buildings-within-buildings, on springs and dampers. Even then, noises get downstairs sometimes. In another studio I worked in regularly, there was a red light added to the ladies toilet on the first floor (studio beneath), to try to prevent (predictable) interruptions. The latter was in a Georgian building, with heavy joists and plasterwork.

 

[Doug71]

I converted an Old school building in to my house and a shop. Some of the bedrooms came over part of the shop and building control were very concerned about noise transfer. We had to get an acoustic consultant involved and the first floor spec was 22 mm chipboard with 15 mm thick acoustic matting over which was like a rubber/foam/rubber sandwich (was very heavy and about £50 m2!) with some engineered oak flooring floated over the top. Certainly not cheap but seems to work.

 

[Chlad]

Is chipboard or plywood better for the bathroom? Premium vinyl click flooring will be fitted on top of that.