Floor preparation - suspended floors

[Paul R Cox]

Sorry this has probably been discussed to death here in the past but...
I have been preparing suspended floors by over-boarding with 6mm backer boards then applying a decoupling membrane. I understand this to be the method for chipboard floors but is this excessive for say, tongue and groove floor boards? or 18mm ply? I ask because this obviously drives up the cost and I want to be competetive while playing safe!

 

[Old Mod]

The decoupler is not necessarily required if your are overboarding with tile backer boards.
It'd depend on the material you're fitting on top, and possibly the environment.
Porcelain, not so much, stone definitely.
Ceramic, could definitely help.
You can use the 1mm antifracture mats, (you may already use them) doesn't need to be full decoupler like Dural or Ditra.

 

[J Sid]

for me its floor size, amount of bounce in floor, tile choice and end use of room.
Depending on the answers to these questions will depend on which method I would use to prep floor.

 

[Dumbo]

The decoupler is not necessarily required if your are overboarding with tile backer boards.
It'd depend on the material you're fitting on top, and possibly the environment.
Porcelain, not so much, stone definitely.
Ceramic, could definitely help.
You can use the 1mm antifracture mats, (you may already use them) doesn't need to be full decoupler like Dural or Ditra.

Why do you refer to 1mm mats as full decoupling i thought 3 ply mats were to allow for limited amount of lateral movement. Do dural and ditra allow more .

 

[Time's Ran Out]

Why do you refer to 1mm mats as full decoupling i thought 3 ply mats were to allow for limited amount of lateral movement. Do dural and ditra allow more .

You do realise it's @_3fall you are questioning!

 

[Paul R Cox]

So I guess there's no real definitive answer and it's subjective. Does anyone have a way of measuring bounce? or do you go on gut feeling?

 

[Andy Allen]

Is it a floating floor?

 

[J Sid]

experience / gut feeling yes
really you don't want to feel any bounce

 

[Old Mod]

Put a cross hair laser in middle of floor and walk purposefully around it, if there's bounce in the floor you'll see vibration in the horizontal line.

 

[Old Mod]

Why do you refer to 1mm mats as full decoupling i thought 3 ply mats were to allow for limited amount of lateral movement. Do dural and ditra allow more .

Yes

 

[Dumbo]

I knew there was a reason I was more comfortable using dural . Funny thing bal reckon their rapid mat is the best thing ever even though it isn't waterproof and can't double up as a tanking membrane like some .

 

[One Day]

Why do you refer to 1mm mats as full decoupling i thought 3 ply mats were to allow for limited amount of lateral movement. Do dural and ditra allow more .

Dural I can't speak for - only used it once and to me it's a cheap copy.
Ditra allows for a crazy amount of movement. I saw test videos Schluter produced but never released - After watching those, I will only ever use Ditra.

 

[Rosco100]

So I guess there's no real definitive answer and it's subjective. Does anyone have a way of measuring bounce? or do you go on gut feeling?

Easiest way to measure deflection on a floor is to put a glass of water (full) in the middle of the floor and jump up and down and if the water exits the glass it not strong enough

 

[Rookery]

Put a cross hair laser in middle of floor and walk purposefully around it, if there's bounce in the floor you'll see vibration in the horizontal line.

That's what I do to show customers just how much bounce there is in their floor and why I'm over-boarding it (with Hardie). I would only uncouple if fixing natural stone, using Durabase most likely or maybe Ditra.

 

[J Sid]

That's what I do to show customers just how much bounce there is in their floor and why I'm over-boarding it (with Hardie). I would only uncouple if fixing natural stone, using Durabase most likely or maybe Ditra.

so do you do the same test with a laser after you have fitted the Hardie to show have much its improved (or not) ?

 

[Rookery]

I would if they ask but they rarely do. Obviously the Hardie is put down as a tiling substrate, not a bounce basher, though it generally does add a bit of stiffness...
Ooooer Missus

 

[Paul R Cox]

The job I've been pricing is natural stone so I'm more concerned. Problem is they have an existing wooden floor down so it makes it more difficult to judge

 

[J Sid]

I would if they ask but they rarely do. Obviously the Hardie is put down as a tiling substrate, not a bounce basher, though it generally does add a bit of stiffness...
Ooooer Missus

sorry, the way i read you other post I thought you we're saying by fixing Hardie it would have eliminated the bounce

 

[J Sid]

The job I've been pricing is natural stone so I'm more concerned. Problem is they have an existing wooden floor down so it makes it more difficult to judge

ok, what size is the floor? Is it ground floor ?

 

[Old Mod]

You mean they have something like an engineered timber floor overlayed which has to come up first?

 

[peteablard]

My house has a suspended floor and after much head scratching I fitted Karndan throughout!! Have converted a few customers to that after explaining the hassle/cost of sorting out deflection

 

[Paul R Cox]

yes

 

[Paul R Cox]

yes to the timber floor question that is!

 

[Old Mod]

All I would do is put a clause in my quote saying..,

After removal of the existing floor, remedial works may be required to strengthen the substrate before installation of new stone floor.
This will be subject to the amount of deflection present, and will be priced on site and will incur an additional cost.

Or something similar, but price for overboarding and inclusion of a decoupler anyway.
It's stone, you will need one regardless.

That's how I'd handle that.

 

[Paul R Cox]

Great, thanks. Sounds reasonable. If using backer and matting would you be inclined to use 6mm backer or thicker?