Overboarding Options

[iwaters]

This conversation originally started in the plumbing section as I was asking about the changing height of a toilet. It probably should be in the Tiling forum though for future reference.

I have a 6' x 4' bathroom floor. The joists are 2" x 7", 16" on centres. The unsupported span of the joists is approx 7 feet. Currently there is 22mm T&G floor boards which are very flat and level. The boards run under walls and into other rooms so ripping up is not going to be an option. As I see it my options are:

1.) Overboard with 12mm ply + Ditra matting for belt and braces.
2.) Overboard with 6mm Hardibacker/Aqua panel
2.) Overboard with 12.5mm Hardibacker/Aqua panel
4.) Hardibacker + Ditra

Which of those options is the best? It is a such a small area so I am not bothered by the cost of the Ditra.

It is not a wet room so the waterproffing properties of Ditra are not required but I want it to last a long time.

 

[Richard C]

Good size joists, standard pitch at minimal span; I’d go with either 12mm WBP ply or 6mm Hardibacker which should be adequate. If you use WBP, acrylic prime the edges & back before you lay, do not prime the tile surface. Make sure the floorboards are will fixed down, add additional screws as required; fix every 150-200mm through into the joists not just the top of the floor boards but check for pipes & cables.

Ditra matting will provide little if any additional benefit for you, it will not additionally stiffen the floor. It’s a waterproof tanking membrane designed for use in wet rooms or as an uncoupling membrane with problem floors.

I advise you read the Tiling Sticky & Forum Archive posts before doing any more work or buying materials, it could prevent you making disastrous & potentially expensive mistakes. There are many things to catch you out particularly if you also intend tiling a suspended timber floor. It’s important to use only quality trade tilling materials of the correct type for your tiles & tile base; cheapo own brand & DIY stuff is mostly crap.

 

[iwaters]

Thanks Richard.

I'll not bother with Ditra then.

I am tempted by Ply now actually as I can use one single sheet with no joins. If I use the hardiebacker it will have at least one join in it.

I've got BAL Rapidset Flexible adhesive, Superflex grout for the floor and Microflex grout on the walls. Dow Corning 785 sealant. Will get some BAL primer if I go with Ply.

I've teared down the plasterboard and will put up aquapanel boards and go over with Kerdi to be sure it is watertight. I've got high mains water pressure and a Megaflow system so it is a powerful shower and want the Kerdi to have confidence in the instal.

 

[Richard C]

I’d also go with the ply in that case. Only acrylic prime the back & edges of the ply to seal them, do not prime the tile surface. Use the Kerdi if it gives you more confidence but I use Aquapanel un-tanked on shower walls & I’ve had no problems.