building a shower base - can i do this?

[dormermike]

Oh I missed that it was on concrete. In that case definitely don't put wood under, use sharp+building sand and cement, basically a mortar mix. Bed the tray directly onto it. Rock solid, it won't crack, rot or split the silicone seal to the wall ever. Just make sure your waste is accessible as otherwise the breaker drill will be the only means of access.

The above is what I did, but my base was already below floor level. I brought it up to floor level. Totally get why you want to keep the drain above the floor. Not pretty, but practical.

Yeah, but that doesn't allow me to raise up the tray does it - I have to raise the tray, so the options are riser kit or timber frame. I can't use the riser kit for aforementioned reasons, so timber frame it is. Mira provide specific instructions for timbers at "minimum 300mm centres" (I think they mean max) siliconed to the floor, with the 22mm+ ply siliconed to the tray, and then you lay that on top of the timbers, attaching the whole lot with silicon. Sounds like a right bodge tbh but thats their instructions.

My post here was asking if i can double up 18mm non-marine ply to make a 36mm base. I'll order some 25mm 800x800 marine which comes out at £90 delivered, which seems outragious, but perhaps thats why the previous professionals elected to use chipboard and that's why i'm redoing all this myself. They also forgot to remove some of the polythene wrap that the tray came in too, so the install was doomed to fail.

Edit phoned mira again and they're now saying not to use silicon even though its in the guide they sent me, as apparently everything can move around. Now they are saying, just 24hrs later, to instead to use "builders adhesive" which is from what I can gather no more nails type stuff. Mad.

I'm going to lay the timbers on the floor, then the 25mm plywood, and sand cement mix then tray.

Maybe I should just get a pro in. lol.

 

[Ivor Windybottom]

Just bed the tray directly onto mortar. Tap it into place while checking the level. Will never move ever.

...just make sure the waste pipe is all solvent weld, not compression and definitely not push-fit junk and absolutely spot-on in the right place, as there's no going back!

 

[dormermike]

Just bed the tray directly onto mortar. Tap it into place while checking the level. Will never move ever.

...just make sure the waste pipe is all solvent weld, not compression and definitely not push-fit junk and absolutely spot-on in the right place, as there's no going back!

Directly onto mortar, on top of the ply, which is on top of the 6x4's beneath ? yep, that's what i'm going to do .

That will give enough room to maintain the wastes etc.

 

[Ivor Windybottom]

You've got concrete below and on top, so much better off to keep it solid all the way rather than sticking some dead tree flesh in the middle of it all.

But yes, if you want access to the waste that you'll never use then you'll need a wooden contraption I suppose.

Most shower wastes aren't accessible these days, other than from above - you normally have a hooked tool to pull the grate out, then you can pull the thing apart, stick stuff down it as you like.

As I stated previously, just use decent solvent weld rather that other botchy options if you're going to make it inaccessible.

Most modern bathrooms would need major demolition if a waste pipe ever leaked. But you hope it's been done right so it won't.

 

[dormermike]

I've got cables and copper pipes below too, not just the plastic waste.

Hoping things are done properly is what id expected when I paid a small fortune getting this done in the first place. Hope is no longer an option.

I appreciate it's better to have solid concrete but it's simply not possible.

Anyway, I know what I'm going to do so I'll crack on once the 25mm ply turns up. Thanks.