Raising bathroom floor level

[diymarkw]

I am tiling a bathroom. I intend to have a glass screen along one side of the shower tray and I have a small area at the end of the show tray which I want to raise by about 40mm so that any water splashes run back into the tray. I would appreciate suggestions as to what material to use to increase the level. I am thinking plywood or hardie backer?[img][img][/img][/img]

[royaloakcarpentry]

The walls have already been tiled. The horse has bolted really. You are going to struggle to make the raised floor water proof and get the necessary falls that are needed to direct water back into the tray. You will not be able to tank it correctly.

The idea is a bad one. The joint will fail between tray and raised area 100 times out of 100.

It would have been far better to have bought a tray which spanned the length of the back wall and had a partial screen.

It would have been far better to make a bespoke tray which would span the length of the back wall.

Hopefully you have access to the trap, from below.

[diymarkw]

I should mention that the tray was installed tight to the plasterboard before tiling. The idea came from an Architect!
Could you suggest the easiest way to ensure that the raised area would be waterproofed? Maybe I could remove the lower tiles to tank it? Would I then have to make a frame across the way in to tank?

[royaloakcarpentry]

You need to think of an architect as a GP. They have general knowledge but when it becomes technical even they ask a consultant that specialises in a particular field.

You also need to think of an architect, on domestic work, as only being as good as the builder who has enough 8oll0x to put them in their place.

That install wouldn't have happened with us because the architect would have been told a few facts about a poor design.


Really you are left with two options and the best and safest is having a complete enclosure for the tray. You could still raise the floor but it won't be getting soaking wet. This is the only way we would finish that job now. Any other way and we would turn the work down, even if you promised another 30K worth of work elsewhere in the house.

The worst options; You can't take the tiles off because you will need to cut the plasterboard out and replace it. Raise the floor and bear in mind it needs to be higher than the tray to allow enough fall to get water back into the tray and away from the join at the walls and also away from the lower floor level. You can tank the raised floor but you also need to partially tank the lower floor. basically you are relying on silicone joints to keep this water tight.
You raise the floor area so the tiling finishes flush with the tray. Tank it and the lower level. Again you rely on silicone joints to keep it water tight.
Tanking will only protect what is underneath it as long as water can't track along the tanking to a weak point and then affect what is below it. Tanking has absolutely no advantage for tiles, grouts, adhesives or silicone joints.

Please put a complete enclosure around that tray. We go to many jobs each year with a similar poorly thought out set up, where we will charge to make it water tight for a limited period of time and offer absolutely no guarantee on what we have just done. In some cases we are now notifying the insurance company not to offer cover if their is a leak. (part of what we now do, inspect
new installs if it hasn't been done by us and then sign them off for the insurance company)

[diymarkw]

Thank you very much for the reply. I wouldnt have any problem telling my architect where to go, problem is I have gone into a Self Build as a newbie and looking for advice from "professionals". I guess if I can get the tray out I could fit a larger one?

I have another similar bathroom to do but with longer 1200 tray so if I tank it all first and then build up the floor I should be ok?

[royaloakcarpentry]

I have another similar bathroom to do but with longer 1200 tray so if I tank it all first and then build up the floor I should be ok?

In one word.....No.

There will always be a weak point where the floor meets the try. This weak point could leak in 4 weeks or it could be 4 years. That is the unknown but it is virtually guaranteed that it will leak at some point. Then it is a question of how quickly the leak is detected.

Far better to have a tray spanning wall to wall and if you can't buy one then it leaves two options. Bring wall out so it fits the space. Make a bespoke tray in situ.



We all get caught out by architects at times because we have to trust them if it is an area we do not know about.