Gap between floor and plaster board

[krakatoa]

I have just put up wet plaster board for my bathroom reno. The walls will be tiled. The problem is there is 30mm gap between the bottom of the plaster and the floor (I used standard 2 * 1.2 m sheets but obviously the floor to ceiling distance is 2.5m). I think this will be too big a gap even after the ac cement and floor tiles are laid. I cant have tiles overhanging the plaster by 30 mm can I (the tiles are 200 mm * 100 mm)? Do I just run a 30 mm strip of plaster around the bottom so the tiles have something to go onto? I guees I'll have to double it up because ac cement is half the thickness of plaster isnt it?

Really appreciate your advice.

thanks

krakatoa

[Fuzzie]

Perhaps fate is telling you to mortar bed the floor tiles and allow a decent fall for drainage?

[krakatoa]

I think if I raise the floor by that much it will at least be one inch higher than the neighboring floor creating an unnatural 'step' when you enter the bathroom wont it?

[pawnhead]

The wall sheets should at least overlap the bottom plate of the framework, so they're supported along the bottom edge, otherwise they could deflect, and your tiles could fall off. There should also be an angle/flashing attached to the studwork and floor before the sheets are installed, as an extra water barrier. If it's well supported, then you could just put a narrow strip of gyprock in there and plaster the joint with tape and base coat only. You shouldn't use top coat because you should apply a waterproof membrane to the floor, and up the walls slightly, before attaching your tiles, and a membrane won't stick to top coat very well.
Top coat should be applied wherever there is no membrane and tiles covering the joints.

[krakatoa]

Thanks John, thats been very helpful, especially about the use of base coat and membranes.

Where the old shower was there is no bottom plate of the framework because it was mortared in... stupidly I didnt think to put a new bottom plate there. Unfortunately I have used a combination of stud adhesive and screws to secure the sheets so I will wreck the sheets if I remove them now.. although a small price to pay in the long run. Maybe I can place and secure a strip of wood in the gap and (like you suggest) add the strip of gyprock and joinit to the sheet and this will make it rigid enough.

What I dont understand is how I could have avoided such a gap? I did as recommended and put the ceiling on, then the top wall sheet and then the bottom. You are meant to hang the sheets horizontally right? So 1.2 m plus 1.2 m only gives you 2.4m... hanging a standard sheet vertically wouldnt of helped. Surely you dont have to lower the ceiling or raise the floor to accomodate the plaster?

[Fuzzie]

I think if I raise the floor by that much it will at least be one inch higher than the neighboring floor creating an unnatural 'step' when you enter the bathroom wont it?

A step into the bathroom is normal when tiles are bedded in mortar over a timber floor. I'm not sure of the regulations where you are, but a floor drain for overflow water and a waterproof membrane in wet areas are all required items around here.

Where the sheeting doesn't match the wall heights by much I think it is usual to leave the gap at the top as it will be covered by the cornice.

[silentC]

So 1.2 m plus 1.2 m only gives you 2.4m

Yes but 1200 + 1350 gives you 2550

[krakatoa]

but a floor drain for overflow water and a waterproof membrane in wet areas are all required items around here

Fuzzie: I like the idea of the floor drain but the plumber didnt suggest it so it wasnt on my radar. I think membranes are mandatory in Victoria and will definitely b eapplying one. You're right, I should have left the gap at the ceiling end. But I wanted to have the wall almost flush against the ceiling in case I didnt go with cornice. We are having a shower above the bath and the tiles behind the shower will go all the way to the ceiling but along the rest of that wall the tiles will only go up 1300mm. My question is how do you install cornice when the same wall has two different levels? Or do you tile up leaving a gap for the cornice? I would think the cornice would look better sitting on top of the tiles as opposed to the tiles butting into the cornice... but I'm open to suggestions as I am sick of making stupid mistakes.

SilentC: You're right, I should have gone with a 1350 sheet... didnt really know about them... I knew you could get them longer but didnt see any wider ones at the local Mitre10... although this would mean cutting the bottom edge and I have read you should try to have the factory edge at the bottom of a wet area.. but if its well membraned it shouldnt matter if its cut or not I suppose?

[silentC]

True, but I would cut it at the top. All academic now though.

As for filling the gap at the bottom, I wouldn't bother. I would really encourage you to put your floor tiles on a mortar bed and form a bit of a fall into the floor waste. Even if they're not mandatory, I much prefer them to the idea of a flat bathroom floor with pools of water all over it. You just put a bit of 25mm angle across the door way to finish the mortar bed and tiles to. By the time you do that and lay the floor tiles, I'd be surprised if you had any gap at all. The only problem I can foresee is that you have to span the 30mm gap with your membrane, which goes in before the tiles. That would mean using a tape of some sort - this will act as a bond breaker though.

For the cornice, I'd be installing that first and then tiling up to. Otherwise you're going to have a gap to fill, and you'd have to pack it out, even on walls that don't have full height tiles - so that it looks the same through the room. I think it will be a much better job and easier to boot.

[pawnhead]

Am I reading you correctly that the plumber say to forget about a floor waste?
I'm with silent there, and I wouldn't want puddles on my floor. That's like my bathroom here that my old man laid flat, and the puddles are annoying.
I'm almost certain that they're compulsory in bathrooms. AFAIK, in laundries you are allowed a dry floor waste not connected to a sewer, or you can have the floor falling towards an outside door, but I think they're tougher with bathrooms.

If I were you I wouldn't bother removing the sheets if they're unsupported, but I would go to the trouble of installing an angle flashing, glued to the floor, and up the wall at least the 30mm gap that you've got. It won't cost that much and a secondary barrier behind the membrane could save some future grief if the membrane fails.
Then I'd install a plasterboard strip, tape jointed as I suggested. It will give extra support to the bottom edge of the sheet if it's just hanging there at the moment, and it gives support to the membrane.

For cornice, you could consider P50 Shadowline as I've done in my renos. You'll lose the shadowline where the tiles slip into it though, and your wall sheets need to extend up to at least the underside of your ceiling framework. Otherwise you could just square set the corners if you wanted.

[zacnelson]

Hello Pawnhead, I loved that picture you linked to of your reno. Could you by any chance post some more photos? I love that square set look around the windows, and the contrast between the greyish blue wall and the white walls. Is that just plaster around the windows, or is it MDF? I did square set plaster around some windows in my reno, and although it's more work than normal architraves, I love the sleak end result. Also, could you explain (if you have time) a little about Shadowline? How is it different to square set ceilings?

Cheers,

Zac