deflection confusion ??

[terry the tiler]

hi! guys and gals ! got a problem understanding deflection and how to cure it. priced a job up with a 5mtr floor with deflection (floor boards). now Ive searched a lot of posts on this subject and iam getting different answers ? some say over boarding cures deflection ? others say it doesn't and that the floor needs to be taken up and extra noggins added to add strength then overboard ? and a small minority say that adding ditra would get rid of it ? .. i personally think (in my opinion) over boarding would not cure it as it would still bounce ? and extra noggins wouldn't work either as the floor would still have vertical bounce ??? am i wrong ? seems to me the joists need to be propped up from below with 3 by 2 etc !!! iam no expert tho

[grumpygrouter]

Depends how much deflection you have terry!

[Dave]

Hi Terry..

Ditra will NOT cure deflection.. 100% sure on that.

Over boarding is the option if a floor has deflection unless it is a floating floor of course..

Broken/loose boards etc need fixing before over boarding...BS minimum is 15mm but that is rare in the uk , so 18mm is next step

[Ajax123]

Ditra won't do it but it depeds on how much deflection ther is as to what other method will be suitable.

[david campbell]

if it's only minimal then you can use ply or backer boards or 2-part adhesive depending on how much movement you think there is

if it's a lot then it's better to rip it all up and start again
i.e -remove floorboards and replace with 25mm ply

[Dave]

hi! guys and gals ! got a problem understanding deflection and how to cure it. priced a job up with a 5mtr floor with deflection (floor boards). now Ive searched a lot of posts on this subject and iam getting different answers ? some say over boarding cures deflection ? others say it doesn't and that the floor needs to be taken up and extra noggins added to add strength then overboard ? and a small minority say that adding ditra would get rid of it ? .. i personally think (in my opinion) over boarding would not cure it as it would still bounce ? and extra noggins wouldn't work either as the floor would still have vertical bounce ??? am i wrong ? seems to me the joists need to be propped up from below with 3 by 2 etc !!! iam no expert tho

That could just be thin floor boards.. the best option is to replace them with 22mm ply butif not then repairing and over boarding is the way but you need to check joist spacing and probs add noggins.

[doug boardley]

Terry,adding extra noggins takes up the slack in individual joists so they can't freely bounce ie one joist is joined to another and restricting its movement. That's how I understand it anyway

[peckers]

hi! guys and gals ! got a problem understanding deflection and how to cure it. priced a job up with a 5mtr floor with deflection (floor boards). now Ive searched a lot of posts on this subject and iam getting different answers ? some say over boarding cures deflection ? others say it doesn't and that the floor needs to be taken up and extra noggins added to add strength then overboard ? and a small minority say that adding ditra would get rid of it ? .. i personally think (in my opinion) over boarding would not cure it as it would still bounce ? and extra noggins wouldn't work either as the floor would still have vertical bounce ??? am i wrong ? seems to me the joists need to be propped up from below with 3 by 2 etc !!! iam no expert tho

deflection bounce can be removed by adding extra noggings between the joists, this will make the joists braced togeather and will stiffen the floor..
However it depends on how much deflection/bounce there is? It may need propping as you say if there is a solid base underneath either by timber supports or by bricking underneath them to give extra support!
over plying will remove vibration, and possibly some deflection!
Ditra will NOT stop deflection this is for laterall movement!

It all depends how bad the deflection is as to what work needs to be carried out before tiling, but this comes with experience as to how much deflection/vibration will be cured with different methods!

hope this helps

[mikethetile]

noggins do take the bounce out of the joists, overbording also works

the reason for taking the boards up is to add noggins, one you have done that theres no point in relaying a chipboard floor and then overboarding with ply, you might as well lay 18mm wbp ply as this by its construction and thickness does not deflect

ply isnt the best surface to ply on , but better than chipboard which is totally unsuitable, so its preferable to overboard the ply with backerboard

[terry the tiler]

thanks for your replies wot is actually moving in deflection ? .. is it the joists its self or the floorboards not having a good contact with the joists ?? i keep thinking iam learning loads but then get knocked back down to earth !

[doug boardley]

thanks for your replies wot is actually moving in deflection ? .. is it the joists its self or the floorboards not having a good contact with the joists ?? i keep thinking iam learning loads but then get knocked back down to earth !

usually the joists move Terry, it's just the spring in the wood

[Dave]

The boards could be the problem.. to thin or to wide a span between joists... the joists could bounce/deflect... this all needs assessing before giving a price or even starting the job.

[terry the tiler]

deflection bounce can be removed by adding extra noggings between the joists, this will make the joists braced togeather and will stiffen the floor..
However it depends on how much deflection/bounce there is? It may need propping as you say if there is a solid base underneath either by timber supports or by bricking underneath them to give extra support!
over plying will remove vibration, and possibly some deflection!
Ditra will NOT stop deflection this is for laterall movement!

It all depends how bad the deflection is as to what work needs to be carried out before tiling, but this comes with experience as to how much deflection/vibration will be cured with different methods!

hope this helps

helps a lot ! thanks

[garythetiler]

remember to use decent wood screws when overboarding or securing floor boards to joists ,I have been to countless jobs where the builders have screwed down floor boards and ply wood with black plasterboard screws these simply dont have the strength or thread grip to secure the boards well enough ,we always remove these and refix using appropriate wood screws

[mikethetile]

wood suspended floors are designed to deflect slightly, this absorbs shocks and cuts down on noise transference, these floors are not really intended for tiling which needs a deflection free floor, so you need to alter the floor in order to tile

so the main deflection is in the joists and the rest is in the floorboards

[Rob Z]

Hi there Terry, check out this thread http://www.tilersforums.co.uk/tiling...oor-spane.html

The "4 S's" are an important concept to learn about when assessing whether a floor is ready for tile. Adding blocking or noggins will help in a local way to transfer a load from one joist to another, but they won't fix a floor that is under-framed and under-sized.