tiling onto chipboard floor

[marcus70]

I am new to tiling, i have just completed a course. My first project is to tile a bathroom floor but it is made of chipboard. If i prime it first will it be ok to tile onto with flexible adhesive ?

[Daz]

Hi Marcus,

I don't know what course you have just completed, but surely one of the first things they advised was that you should never tile onto chipboard, or MDF for that matter. Both chipboard and mdf are basically wood chippings or paper shreds that are heavily compressed together to form a "wood" substrate. This means that moisture from the tile adhesive can cause the substrate to de-laminate, i.e cause all your tiles to be stuck to thin air.

You will need to overboard before tiling and can use 12mm plywood screwed and stuck or better still, go for a fibre board such as Wedi or concrete board such as Hardie Backer.

Still use a flexible adhesive and flexible floor grout. Are you fixing ceramic, porcelain or stone?

Regards,

[tfs]

welcome to the forum Marcus,

I know where you are coming from mate. You see DIY stores selling products that claim to be suitable for this type of project however, many tradesman would rather not tile directly onto this type of subfloor and the preffered option would be to sheet over with ply or type of backerboard.

Iin my experience you can get away with 9 -12mm plywood providing the floor is in good shape but, if you are looking to follow manufacturers instructions then you will probably find that they will specify a thickness of ply which would be likely to be at leats15mm.

I would highlight any increase in floor level to the customer prior to commencement of work. Be sure to tell them that this would be unavoidable or they may think that another tiler can do the work whilst avoiding any increase in floor level.

You can find freshold bars for changes in floor level to meet most requirements. you can pick these up at tile distributors, flooring distributors or even carpet retailers and B&Q etc.

[grumpygrouter]

The reason that BS states that 15mm minimum exterior grade ply is used on floors is to impart enough strength to eliminate deflection as much as possible. It is deflection of floors that causes most problems not so much the moisture aspect.

Any timber floor is likely to move with differences in temperature/moisture, just some more than others. Chipboard itself is not the best susbstrate to tile on but with proper preparation and protection it can be done IF ABSOLUTLEY NECCESSARY. However, the additional cost of the adhesives and primers and the like to do so, can make it more cost effective to board out.

I recently tiled an enterance hall with a chipboard substrate. The floor was solid ( i did the glass of water test) and overboarding was out of the question. I sought advice from my prefered adhesive manufacturer for timber floors and was given 2 alternatives to do the job.

The job is now completed and the customer is happy. Only time will tell if the tiles stay down but I am sure they will.

[macten]

So what's the method then Grumps?

[grumpygrouter]

The floor I tiled had previously been covered with parquet. The removal left the black horrible bitumenous type glue all over the floor. I was given the following alternatives

1. Prime the floor with Ardex p82 and when dry tile with Ardex-flex 7001, with appropriate flexy grout to finish.
2. put down a layer of Ardex Feather Finish, leave to dry and then tile as above.

I chose option 2 as it gives a small amount of smoothing. Was able to start tiling after about an hour or so.

I think the P82 (epoxy primer) takes a little longer to dry.

Normally for Ardex-flex 7001 Ardex P51 is the normal primer but for my purposes P82 was recommended.

If you look at http://www.ardex.co.uk/pdfs/ARDEX-FLEX%207001.pdf
you will see that flooring grade chipboard is mentioned in the Surface preparation section on page 2.

BAL Fast Flex will also do a similar job but is way more expensive.