Building a plinth for the bath

Hi
We are in the process of doing our bathroom and will be building a plinth which a freestanding bath will be on and looking for some advice on the best way to build it.

The area will be approx 2280mm by 864mm. The joists in the floor run horizontally, floorboards vertically. There are pipes and a waste under the floor area too.

We are thinking of using 3'x2' timbers to baton it out and are not sure whether we should do this horizontally or vertically, initial thoughts were vertically so it is at right angles to the floor joists, either way we would have vertical batons for where the bath goes. We could also use a whole sheet of 8'x4' 18mm ply or cut it to smaller manageable pieces for the floor.

How should the batons be fixed, as pipes are under I'm thinking of how it could easily be dismantled if it needed to be.

The finished floor would be bamboo flooring and we are thinking of laying this horizontally (depth of 864 is width of nine planks) though I think ideally this would normally be vertical to draw the eye in we are limited on the depth it can be and laying vertically would mean each one has to be cut.

Thinking of having the kickboard made of a strip of the 18mm ply and we will be putting in some little LED decking lights in and staining the ply to match the colour of the bamboo.

Would be grateful for any advice.

Love the thought of vertical floorboards , non-horizontal joists are not uncommon but try again using words like parallel, perpendicular etc. The idea is to spread the load from the bath across as many joists as possible, so you'll want to batten across the joists. Was there a bath in this room before- if not then you might want to think about the additional imposed load on the joists and whether they're up to the job. Or if you're moving the bath from near the wall (where the joist ends are) to the middle of the joist span then again have a think about the change in loading, especially if the room is largish (3m or more)

Is that bamboo laminate flooring you're considering?- entirely up to you of course but laminates don't generally perform well in wet areas.

I'd be screwing the 3 x 2 battens down with my trusty impact driver and doing the plumbing properly so I don't have to worry about taking the whole thing apart again (which would be no fun with the bath to come off first would it)

And forget stain matching the ply to the bamboo- it'll look like a mistake. Paint it instead to match the colour of the bath or (if you can hide the top) clad it with a strip of your bamboo floor.

Have a little think about electrical zones for your deck lights (which sound terminally tacky to me but I don't have to look at them). Yes the LEDs may be at 12v but you'll have a driver for them somewhere which won't be at 12v, not to mention a switch or controller of some sort.

Well I'm glad I bemused you but at least you understood what I meant! The bath is moving place but before it was the original cast iron bath so the joists should be pretty strong if they could hold that up. I'll stick with my plan of batons across the joists then so it spreads the weight. Would you screw the batons into the floor joists? What about the Ply is it best to use as large pieces as possible?

I trust my plumber would do the plumbing properly but you never know what might happen so I think it's best to make it as easy to disassemble as possible. The LEDs will be wired in and will only be able to be turned on via a switch outside of the bathroom. They are being installed by an electrician who suggested them and I'm sure I've read that providing the space under the bath cannot be accessed without using tools, that space is considered to be out of Zone so they should be fine!

Yes I'd screw the battens to the joists- reduces the odds of the ceiling below detaching itself due to vibration or a stray hammer shot . Make sure you use good screws though- the type that actually pull the timbers together rather than just fixing them where they are. Is the ply for the plinth or the rest of the floor- if you're using laminate floor then stability isn't as critical as for tiles or similar, the original floorboards will probably work (though you will get a smoother flatter surface with ply). As long as any joins parallel with the joists are on a joist (or supported) then you can do it in bits, though doing it in 1 sheet is always more satisfying. If the ply is for the plinth then again one piece is better but (given your maintenance access) 2 or 3 pieces might be wiser, joints parallel to the battens either on the battens or supported.

The maintenance access for the plumbing- thinking on I suppose a freestanding bath would be fairly non-destructive to remove if you needed to so your scheme does make sense.

And yes you're correct about the zoning under the bath if tools are required & switching externally obviously works, though you could have a 2nd pullswitch to confuse the unwary (if you have children they'll take great delight in messing with the externally switched bathroom lights. I know I did)