Hardibacker v's Ply confusion

[Holohana]

Hi all, hope you can settle some confusion ive got.

Ive got a job where im doing some floor tiling and the builder is boarding out the floor for me but called today nd amongst other things asked to see how I would do it.

Told him I’d use Hardibacker, he was using 6mm ply himself and always does, and id lay this on a bed of flexible adhesive then screw every 300mm.

The area is 85m2 so comes in at just under at £1,000k for the boards plus addy plus labour. He balked at the total cost and said he’d just use what he’d already planned to do.

My labour was dirt cheap to lay the board, £100 a day, as got a free week and could do with a week of simple screwing.

The board going into 8 units all the same size so cut one lot of board and you’re away for the rest so really easy.

Joiner quoted £10m2 for laying ply plus ply so I’m well cheaper on labour and frees him up to crack on with other stuff on the development.

Now this is where the confusion starts.

When laying Hardibacker, 6mm on floors as per the spec which to start with I think is too thin, it states that you need a bed of adhesive applied with a 6mm notched trowel and then screwed.

My question is when laying simple plywood over boarding why don’t you need to use a bed of adhesive in that instance?

Technical at Hardi said its to make sure you don’t have any air gaps under the board which would allow movement and cause problems.

I get that point but couldn’t the same happen when laying ply?

Thanks in advance for what im sure will be compelling reasons why you do for one but not the other.

[whitebeam]

If ply your right about a screwing every 300mm so the bulk of screws will support it, Hardie backer I Personaly don't put screws in every 300mm I use about 8 and put extra sbr with the addy between hardie and floor, even forgot to use fixing's once never had any problem's

[DS Tiling]

The adhesive helps with any undulations in the floor but also aides with making the cement board more rigid. The ply is usually 12mm plus so is fairly rigid to start with. You haven't said what the original substrate was but personally I wouldn't lay on 6mm ply on a floor that size.

[GazTech]

[quote=Holohana;57595][FONT=Times New Roman][SIZE=3]Hi all, hope you can settle some confusion ive got.[/SIZE][/FONT]

[FONT=Times New Roman][SIZE=3]Ive got a job where im doing some floor tiling and the builder is boarding out the floor for me but called today nd amongst other things asked to see how I would do it. [/SIZE][/FONT]

[FONT=Times New Roman][SIZE=3]Told him I’d use Hardibacker, he was using 6mm ply himself and always does, and id lay this on a bed of flexible adhesive then screw every 300mm.[/SIZE][/FONT]

[FONT=Times New Roman][SIZE=3]The area is 85m2 so comes in at just under at £1,000k for the boards plus addy plus labour. He balked at the total cost and said he’d just use what he’d already planned to do. [/SIZE][/FONT]

[FONT=Times New Roman][SIZE=3]My labour was dirt cheap to lay the board, £100 a day, as got a free week and could do with a week of simple screwing. [/SIZE][/FONT]

[FONT=Times New Roman][SIZE=3]The board going into 8 units all the same size so cut one lot of board and you’re away for the rest so really easy. [/SIZE][/FONT]

[FONT=Times New Roman][SIZE=3]Joiner quoted £10m2 for laying ply plus ply so I’m well cheaper on labour and frees him up to crack on with other stuff on the development.[/SIZE][/FONT]

[FONT=Times New Roman][SIZE=3]Now this is where the confusion starts. [/SIZE][/FONT]

[FONT=Times New Roman][SIZE=3]When laying Hardibacker, 6mm on floors as per the spec which to start with I think is too thin, it states that you need a bed of adhesive applied with a 6mm notched trowel and then screwed.[/SIZE][/FONT]

[FONT=Times New Roman][SIZE=3]My question is when laying simple plywood over boarding why don’t you need to use a bed of adhesive in that instance?[/SIZE][/FONT]

[FONT=Times New Roman][SIZE=3]Technical at Hardi said its to make sure you don’t have any air gaps under the board which would allow movement and cause problems. [/SIZE][/FONT]

[FONT=Times New Roman][SIZE=3]I get that point but couldn’t the same happen when laying ply?[/SIZE][/FONT]

[FONT=Times New Roman][SIZE=3]Thanks in advance for what im sure will be compelling reasons why you do for one but not the other.[/SIZE][/FONT][/quote]If this 6mm backer is onto chipboard then fine, no addy reqd. I have never had problems, but on T & G it's different story....Gaz

[Holohana]

floor is chipboard on 2 x 2 joists. All small units totalling 85m2 with the max area being 5m2. Office toilets x 2 in 8 seperate units so not one massive area.

Builder is using 6mm ply so in theory he should be using adhesive too then?

I thought 12mm would be rigid enough, guess you could still have gaps though?
----

Originally Posted by Gaz

If this 6mm backer is onto chipboard then fine, no addy reqd. I have never had problems, but on T & G it's different story....Gaz

Ive never had problems either but always been domestic, not commercial and not 85m2 polished porcelain!!!

[GazTech]

[quote=Holohana;57667]floor is chipboard on 2 x 2 joists. All small units totalling 85m2 with the max area being 5m2. Office toilets x 2 in 8 seperate units so not one massive area.

Builder is using 6mm ply so in theory he should be using adhesive too then?

I thought 12mm would be rigid enough, guess you could still have gaps though?
----



Ive never had problems either but always been domestic, not commercial and not 85m2 polished porcelain!!![/quote]Fair point cover all your bases on this one Holo....Gaz

[Dave]

If you are not happy with the builders prep work...then say so to him...if he won't change it..then don't do the job...coz if it does go wrong it is you who will be to blame as well.......

[Holohana]

laid out all the options to him so he is aware and the pros and cons of all alternatives.

He's done plenty before so he knows what he is happy with, He knows what addy ive quoted for and will be using so he knows i know what im doing.

12mm ply isnt an option for him!

[GazTech]

[quote=Dave;57671]If you are not happy with the builders prep work...then say so to him...if he won't change it..then don't do the job...coz if it does go wrong it is you who will be to blame as well.......[/quote]Or ask him to sign a waver, stating you had disagreed with his preparation .....Gaz:yes:

[Dave]

Originally Posted by Gaz

Or ask him to sign a waver, stating you had disagreed with his preparation .....Gaz

Yes! theres that option as well..............

[Holohana]

i guess you can therefore use 6mm hardibacker because the adhesive bed vreates the rigidity then?

Waivers, are they actually worth the paper they are written on?

[grumpygrouter]

Does anyone find that 6mm Hardiebacker is actually "flat"?

Grumpy