Why are modern floors always so creaky?

Discussion in 'Floors, Stairs and Lofts' started by MisterBoy, 20 Nov 2021.

  1. MisterBoy

    MisterBoy

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    One of the things I dislike about new build houses is that the floors are always noisy.
    In our own, old house the loft has been converted before we moved in and we have the same thing with the modern floor. It feels insubstantial as you walk on it.

    We recently had a 1 storey building built. We went with good solid suspended joists properly spaced, 22mm weyroc screwed down nicely, by someone we know to does good work.
    Same thing, the floor is noisy and less solid feeling than our house.

    Why is this? Is it down to old floors being overspecced - huge 8x3" joists etc - or to the difference between sheet flooring and boards, or something else?
    We have some floors in the house that need work and I'd hate to 'improve' them the same way.
     
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  3. JobAndKnock

    JobAndKnock

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    Was the Weyroc glued down to the joists? Were the tongues properly glued and butted up tight? (I use a piece of 4 x 2 and a sledge hammer to achieve this) Did he leave a 5 to 10mm gap at the edges of the floor for expansion? (which also reduces creaking) Have any services been run through the floor, like pipes or wastes, which touch the chipboard where they go through? What size joists were used, and at what centres, what grade (C16, C24, etc) and how long are the joists? Do all the end joints land bang on top of joists? In order to track down a problem it is necessary to gather a lot more information - floors don't just creak because of the material they are made with. I've done enough commercial stuff (offices, restaurants, pubs, shops, etc) with P5 T&G to know that if what I put in creaks, they'll have me back in an instant. I also know that without an on-site inspection this sort of stuff is all but impossible to snag - it could be something as simple as a few nails holding a stud wall sole plate not connecting properly, or it could be one or more of many other factors

    If you really want a floor which doesn't ever move you can always go for a double or triple skin 9mm plywood diaphragm floor - but they aren't cheap and you have to watch the installers like a hawk to ensure that they are doing the job right as there is a tendency for the more fly by night types to skimp and cut corners (spoken with my "black hat" on)
     
    Last edited: 20 Nov 2021
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  4. MisterBoy

    MisterBoy

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    It's not a problem in the new building - I use it as an illustration rather than a complaint. I would guess glueing is something that's typically omitted but then my question is why such detail is needed. In an old house they just nailed boards onto joists. Of course you get loose/creaking boards as nails slip but that takes quite a while whereas if you go in a new house, the floor 'wobbles' almost.

    Is it mainly down to modern methods paring down thickness/size so you have to do it properly whereas in the past the sheer weight of the material did a lot for you? Or are 8x4 sheets fundamentally different to individual boards how they work?

    Interesting point about commercial use - you're right those floor are always solid. But IIRC building regulations for commercial floors require them to be substantially stronger and I assume you're not just laying a sheet of weyroc - you have a subfloor, or much more thickness? I was watching how a guy had it done in a renovation in the US and it seemed his floor ended up a couple of inches thick!
     
  5. JobAndKnock

    JobAndKnock

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    In Victorian work, something I have got a more than a few years experience of, there was a tendency to over engineer. Modern buildings tend to be built to a certain structural standard with some S/Es going far closer to the minumum than I personally like (one reason I prefer working on larger scale projects where there is slightly less tendency to under engineer). In the past I feel it was a combination of heavy structural engineering combined with use of appropriate (at the time) fixing methods, but even so correct installation was still a must. 8 x 4ft sheets seem to have come in to general use for housing in the late 1950s/early 1960s on the grounds that they were faster to install - we were certainly using them on commercial sub-flooring in the late 1970s, although I do remember the workshop having to edge groove all the boards on all 4 sides as well as send out loose 1/4in plywood tongues with them which were glued in place on every joint (and extra bearers or solid strutting installed where joints weren't fully supported - note that we didn't glue to the joist in those days). In house building there were a lot of fly by night builders who turned a blind eye to the need to do this and who, with the widespread introduction of gas nailers in the 90s and early 2000s permitted sub-floors to be nailed rather than screwed. This, together with the poor got chipboard sub-flooring a bad name and floor material manufacturers took steps to improve the image of their materials by introducing moisture-proof grades (P5 chipboard), smaller boards (2400 x 1200 as opposed to 2440 x 1220mm), putting well-designed T&G joints on their boards:

    Caber TandG Chipboard edge detail.jpg

    and insisting on the use of the appropriate adhesives and fixing techniques. This means that yes, installing sub-flooring isn't just wham, bam, thank you ma'am - it is an engineered product and needs to be installed appropriately unless you ewant the darned thing to creak and crack. Personally I'm somewhat less than impressed by the standards of some of the guys I've had working for me over the years, but slip-shod and slap-dash seem to be the modern approach for at least a percentage of the guys we get.

    In terms of old planked sub-floors you seem to think that they are just thrown in any old way. This simply isn't true. A planked floor needs to have a gap around the edges as well (to avoid wicking of moisture from the exterior walls and to allow for expansion), the correct fastenings need to be used (e.g. cut nails or ovals, or sometimes lost heads for invisible nailing - round nails cause splits and the heads sit proud, so OK for fencing and sheds, but not for flooring planks) and planks need to be cut to join end-to-end on a joist. You also have always needed a couple of flooring cramps to do the job right:

    Flooring Cramp.jpg

    AFAIK they (or an equivalent) have been around from at least the 1870s and are still used. Even before the metal ones came into use wedges and bars were used to pull joints up. These days they are lessmcommon (as is T&G planking for that matter) and there are quite a few modern equivalents on the market which also get used for decking and the like:

    Floor Cramp - Modern.jpg

    For lower traffic areas in offices, pubs or restaurants it is not uncommon to have 22mm P5 T&G (albeit on 300mm centres at times). Higher traffic areas may get one, two or three skins of something like 18mm T&G spruce plywood with specific nailing patterns. This has started to come into some domestic (conversion) work as well, such as a recent job where the entire top (sub-)floor of the building (25+ duplex apartments) was installed as a double skin of 9mm plywood glued and nailed in place (somewhere around 500 no. 50mm ring nails for every sheet with very specific patterns for the lower and upper sheets) followed by a layer of 15mm cement fibre board with acoustic caulked joints. Amazingly those sub-floors are very taught when properly installed just the plywood alone (all the cement fibre board adds is fire proofing, heat and sound insulation) - but then they are also designed to be a stressed skin which binds the outer walls together (with additional strapping) and they are expected to be both lightweight, and very stropng. Very thick sub-floors as in your example are not necessarilly such a good idea - the require a more substantial structure to carry the load (especially in a multi-storey building) and cost considerably more in monetary and installation times as well. So thick isn't necessarily better - properly installed is

    As an aside, from your previous comments I have gained the impression that your Weyroc was installed as 8 x 4ft sheets. Is that correct?
     
    Last edited: 21 Nov 2021
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  6. John D v2.0

    John D v2.0

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    Our architect specified 18mm flooring ply screwed down, for our extension, and we didn't know at the time about the matter, but we are very glad, cost 30 quid a sheet so maybe double that of chip board but you don't really get a peep out of it.
    There are one or two tiny creaks in the front bedroom that we retro fitted the same, but those are 100 year old twisted up joists with plenty of notches in them.
    Also easy to get up without having to deal with glue. But based on my experience i wouldn't use anything else.
     
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  8. MisterBoy

    MisterBoy

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    Wow, thanks for the thorough reply. Very interesting - I never even heard about flooring clamps before.

    And yes I think so, although a better answer would be "whatever the building yard would most commonly have". They certainly looked around that though, similar to insulation boards and OSB sheets in size. I'm not sure what centres but I think 50-60cm - I recall it went through an engineer who signed off on all the structural side if it.

    When a modern floor does creak and you can feel it 'bounce' slightly when someone walks heavily on it, what exactly is going on? Is it the flooring moving in relation to the joists as they bend slightly and getting some play? Is the role of the glue to allow a slight flex without it rattling/creaking?

    You're right that as a layman I got the impression you basically just had to securely fasten your boards to the joists, allow a slight expansion gap and that was it :) Always interesting to learn more about the proper way in case I ever feel tempted to do this myself. I would be gutted if I pulled up my pitch-pine boards, spent loads of time on money on new flooring, ages installing it only to find it was worse than the 100-year-old floor I'd replaced!
     
  9. JobAndKnock

    JobAndKnock

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    Sorry - long post with lots of piccies

    A couple of points here, John - almost anyone in the structural side of construction will tell you that the price of 18mm WBP plywood is (and has for a long time) been more than £30 a sheet (these days try more like £45 to £50 for decent quality 18mm WBP plywood if and when you can get it) and also that the quality of WBP hardwood plywood has deteriorated markedly over the last 10 or so years, principly since the Chinese came into the market and started to edge out (IMHO better quality) Indonesian, Malaysian and West African supplies. Sadly Brazillian stuff, which was often very high quality, disappeared even further back - possibly because they've more or less clear felled large areas of rain forest and are running out of timber to turn into plywood. You also imply that chipboard material is the problem - well, sorry, but it isn't. The problem is more often than not poor installation practices combined with lack of adequate supervision, but that also occurs with plywood sub-flooring, although I will admit that with plywood onto traditional solid wood joisting things are slightly less critical and you can get by employing a more slap-dash approach (even if it does result in creaking at a later date because no tongues were installed). One other point, which is becoming far more important - hardwood plywood of the types so often used for sub-flooring in the past is a rain forest product and as such it is unsustainable in the longer term and is a major part of the ongoing problem of deforestation in the tropics. Chipboard and OSB on the other hand are manufactured from plantation-grown softwoods, a rebewable resource where at least some of the materials used in their production can be locally sourced (becoming increasingly important in our post-Brexit economy, let alone in terms of carbon emitions)

    Did your installer groove every board edge and glue in a 1/4in plywood tongue? I've rarely seen that done in domestic work, whereas it was often done in commercial work because it minimises the chances of creaking.

    Modern chipboard and OSB sub-flooring products tend to come in 600mm wide "planks" with tongue and groove edges all round. AFAIK wiith the exception of some specialised plywood sub-flooring (e.g. spruce - which comes as 2400 x 1200 mm T & G sheets) full size sheets come with square cut edges - so if you don't want them to creak you need to route out a groove in the edges and install a glued-in tongue. I've pullked up and replaced quite a bit of chipboard in recent years but verey rarely seen this done on non-commercial jobs.

    500 to 600mm centres is very wide and when you do see iy it tends to be for composite I-beam joists like these:

    Composite I Beam Joists.jpg

    or space joists:

    Space Joists.jpg

    or the timber equivalent, the open web flooring truss:

    Open Web Floor Trusses.jpg

    The thing about those, they are generally specified for use with a stressed skin sub-floor (either plywood or chipboard) - which means the sub-floor must be glued and screwed (or nailed) T&G sheets where the boards are glued top the tops of the joists and also at the tongues on the edges. These days S/Es also tend to specify 22 or 25mm flooring on such wide centres. "Just screwing it down" onto these modern joists simply won't work

    In a traditional solid timber joist floor structure the bounce is often caused by the joists being marginal for the applied load, assuming that there are no other structural defects such as over notching or over drilling of the joists or problems with their end supports. When you load a joist, if it is properly secured to the sub-floor (by being glued and screwed) the only thing the joist can do if it is heavily loaded is to bow a little and then twist sideways (note that the glue reduces any tendency to bow by supplying a far greater connection area). The way that twist is cured is by adding herringbone or solid strutting between the joists (BTW tyhese are NOT noggins). Solid strutting should be be the same thickness as the joists and between 80 and 100% of their depth and very tightly fitted to function correctly

    Herringbone Strutting.png
    Above: Modern metal herringbone strutting
    Below: Traditional wooden herringbone strutting
    Wooden Herringbone Strutting.jpg

    Solid Strutting.jpg
    Above: Solid strutting
    Below: How strutting transfers side load (twisting)
    How Strutting Transfers Loads.jpg

    What the strutting does is to transfer the sideways twisting load into the adjoining joist, and the one adjoining that and so on. This results in a considerably stiffer floor with noticeably less bounce in it.

    Whilst herringbone strutting (modern and traditional) is lighter and performs better than solid strutting, it is effectively only possible to install it before the floor is fitted, meaning that solid strutting is the choice for retrofits When installed in new builds it is cheaper and faster than herringbone because it is often possible to use joist end offcuts (where joists have been trimmed to length) to make up the strutting

    Please note that the following applies to conventional timber joisting - for composite methods (as illustrated above) input from a structural engineer to cure structural faults may be required

    BTW as an aside you might like to know that traditional dance floors were deliberately built with slightly undersized joists and minimal strutting to ensure that the floors actually had "spring" or "bounce" in them., This is taken to extremes in theatre stages where getting the appropriate amount of "spring" in the stage floor can be essential to prevent dancers (e.g. ballet) physically injuring themselves by performing on too "dead" a surface

    Even in "the good old days" there was a bit more techique than that. When you get involved with modern lightweight structures it becomes a bit more technical than that and manufacturers'/specifiers' "advice" needs to be obtained and adhered to for best results

    At the end of all that my brain hurts
     
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  10. MisterBoy

    MisterBoy

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    Our building was a rather atypical 'raft' type design - suspended 'cells' built onto piles (effectively) on a 2x2m grid basically. So each 'cell' was a 2x2m box made from C24 8x2 (I think, or it might have been doubled 6x2 or some mixture). We had 2 extra pieces subdividing the cell into 3 strips (like a neapolitan ice cream!) which would equate to 60cm centres but they were short runs - 1.8m if memory serves - and I'm pretty sure there were noggins as well.

    I think you're right on reflection, it was probably 600mm flooring not 8x4 if that's the norm, as they were definitely TG.
     
  11. phatboy

    phatboy

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    Thanks @JobAndKnock , I feel smarter after reading all of that! I love detailed explanations.
     
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  12. MisterBoy

    MisterBoy

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    It's great... echo these thanks.
     
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