Installation of hardiebacker 250/500

[John Benton]

Great post thanks Bri, very helpful, just a quick question, when you say that any deflection should be rectified before laying the Hardiebacker, do you mean by say laying SLC first to even it up?, I have a chipboard floor to do that is out by 10-15mm in places and was thinking of self levelling first then putting the Hardiebacker down onto the SLC with SPF, if this is acceptable would the SBR be ok to prime the chipboard with ready for the SLC (which will be Weber Floorflex)?

The deflection is the movement up and down. By fitting extra noggins between the joists @ 450mm centres this would generally eliminate deflection. Then screw the chipboard back down including fixing to the extra noggins.

 

[Plumbing Tiler]

Thanks John, sorry my mistake!, the floor is actually very solid and therefore deflection free, I do usually add extra noggins where there is movement as I like to go for the belt and braces approach whenever possible but I don't think it would help on this occasion as I think the problem with the level is caused by the joists resting on the stone chimney breast from either side and this seems to be causing a raised "bump" in the middle of the room so at the sides it "dips" by 10-15mm, how would you deal with this difference?, I am thinking of putting SLC on the side bits to bring them up to level of the centre of the room before overboarding the lot with Hardiebacker.....cheers

 

[Mr Tiler]

Hello bri brilliant and in depth post mate should be made sticky...but quick question... Is it not better to use Silicon between the joints of the boards due to expansion? or is that over doin it? Cheers mate

 

[Martino]

I dont understand what is wrong with PVA after all your sticking it to wood lol??...if there are voids then yes use some rapid set but if the floorboards/chipboard floor is allready flat then i think i would p.v.a onto it...i no of a professional who actually does this. just have never myself thats all...YET. lol

 

[DHTiling]

Do you really want a pro answer to this..

I do hope it gives you a hard on.

 

[Martino]

Obv. your reply seem to give you a hard on Dave....Wood and pva work very well. I will be trying this method in the future for sure on flat floors. on uneven floors ill stick to adhesive.

 

[White Room]

Obv. your reply seem to give you a hard on Dave....Wood and pva work very well. I will be trying this method in the future for sure on flat floors. on uneven floors ill stick to adhesive.

Can't believe this post...

 

[Mr Tiler]

Can't believe this post...

in all fairness the useage of adhesive is simply to fill the voids (which is noncence of course it creates a bond between substrate and cement board!) but if the floor is flat what would be the point in using pva or the correct primer? are you expecting the pva to act like glue? i.m.o if the floor was flat as a pancake I would simply use a smaller trowel.

 

[White Room]

You show me a dead flat Ash, very rare....

 

[AliGage]

I dont understand what is wrong with PVA after all your sticking it to wood lol??...if there are voids then yes use some rapid set but if the floorboards/chipboard floor is allready flat then i think i would p.v.a onto it...i no of a professional who actually does this. just have never myself thats all...YET. lol

Does Mr Hardie suggest to stick it with PVA?

 

[beanz]

If the floor is "dead" flat, PVA wouldn't hurt. At the same time, it would be of any added benefit either!?! Why would you need to glue it, if its going to be screwed at 200mm centres anyway?

I too am wondering about the expansion gaps... I can't imagine that tape keeping the adhesive out!?!