Subtle movement/vibration on suspended ply floor - Tiling?

[outmyway]

I've taken up my chipboard and replaced with 18mm WPB ply.

If I jump up and down or go on tip toes and bang my heels down in certain areas I get a subtle vibration a few feet away.

I've taken the ply up and added extra noggins and re-levelled the joist, but still cant totally get rid of this.

Will there always be a subtle movement on a suspended fllor?

If it OK to tile onto - I plan to use ditra matting?

 

[mikelyonstiling]

Are you fixing at 15cm centres?

If you are, then ditra matting is great.

Mike

 

[Richard C]

Jumping up & down on a floor is hardly a realistic way to assess the degree of flex, especially if you weigh 20 stone ! A suspended timber floor by its very nature will always have a degree of vibration & even flex when subject to a severe test, what’s important is that it doesn’t fall outside that which a quality trade flexible adhesive/grout can easily cope with. Each floor should be individually assessed before deciding the thickness of WBP required, in many cases 18mm is sufficient but sometimes 22mm or even 25mm is required, this must be screwed down every 15cm as stated.

What size, pitch & span are jour joists & what's the size of the room?
Also what are your reasons for using Ditra matting over the WBP?

 

[outmyway]

Thanks for the replies, maybe I am being too fussy ...

The joists are 16" spacing and yes screwed down every 15cm.

The room is a kitchen dinner I have recently knocked through, that also has an extension into half the double garage. So its very long (about 8m) and one end is joists suspended over screen and the rest are above a lower floor of the house.

I feel their might be a temperature variation in the room because of the above and prefer to use ditra. My tiller used it in a bathroom with Traveretine and I was impressed with it (I replaced the floorboards with ply after in the adjoining en-suite which sit on the same joists and had no cracks in the tiles or grout, despite a lot of heavy duty work to remove well rooted chipboard).

Is their any disadvantage of using Ditra matting?

Is BAL flexible adhesive the best to use?

 

[Richard C]

In many cases, 18mm WBP is sufficient in bath/shower rooms with 200 x 50mm joists @ 400mm pitch providing the span is not too great; by their nature, such rooms are generally both light use & loading. However, a kitchen/diner is a heavily loaded/used area &, personally, I would have gone for 25mm WBP, even sistering some of the joists if I felt it necessary.

Ditra matting is a de-coupling membrane & I wanted to understand your reasons for using it. Correctly laid, it will not affect the distributed load the tiles will take but it will reduce the maximum permissible impact & point loads; this should be something you consider when selecting tiles where there is a strong possibility of objects being dropped on the floor - in the kitchen for instance! You don’t say what the floor width is but at 8m long, Ditra matting alone may not be sufficient & you may be getting near the limit without the need for an expansion joint; possibly at the junction between the original property & the garage but it depends on the layout. In the 4 years or so I’ve been tiling, I’ve not tiled larger than 36 sq/m & that was square so I don’t profess to be an expert on expansion joints. tictic , JCT or one of the others may be better able to advise you here but, if not, I would advise you contact Schulter with your specific project details. Have a read here;
http://www.schluter.co.uk/2723.aspx

I use nothing but BAL because I know it works for me but there are other quality adhesive/grouts that perform equally as good.