18mm board to spread load under bath.

[securespark]

A while back some kind soul suggested the above in response to one of my posts, but I cannot find it now .

I'd like to use 18mm board to put under our new bath (1800 x 800 double ended) to help spread the load better.

However, looking at the various plys and OSB's, I'm not sure which is best.

I want the strongest & most proof material.

Some plys are structural, others are not. OSB's seem good too.

Which would be my best bet, please?

Cheers.

 

[hotrod]

OSB is a bit pony to be honest secure. If you need to use an 18mm ply get WBP ply.

If you want the strongest use 22mm or 25mm WBP - just depends on what FFL you have to work to I suppose. If you could explain what the ply is being used for you may get more detailed/specific advice.

hth

 

[securespark]

Thanks. The ply is being used purely to spread the load of a fully laden bath across the floor more evenly.

Rather than fix the bath down to the T&G boards, I'll lay a sheet of ply down & put the bath on top.

 

[masona]

If you can afford it, maybe think ahead by replacing all the floor with WPB/Exterior plywood, while you're at it you can also check all the wirings/pipes/laggings/ added noggins if loose joists or add a shower cable etc. Plywood floor will feel more rigid & quieter plus if you ever decided to have floor tiles in the future, it's ready

 

[securespark]

I'll think about it next time I get paid!!

 

[jack_s]

Maybe use some bricks or similiar

 

[jabuzzard]

18mm board of any description is not going to usefully spread any load from a bath. 10mm plate steel would work but would probably just end up adding more weight.

If you are genuinely concerned about the load from the bath on the floor, then you need to rest the bath on some new joists that go across the existing joists. Anything else is a waste of effort and money.

 

[hotrod]

I'll think about it next time I get paid!!

I would go along with what masona said. If you can, remove the existing T+G flooring and check you're happy with the state of the existing joists. You can also check the joist section size and span whilst you're at it. If you're confident all's good for your new bath you can then replace the sub-floor with 22mm WBP ply.

 

[TicklyT]

4X2 bearers laid across the joists (in line with the floorboards) will do more to spread the load than a flat sheet of ply.
It's usually possible to wind up the undercarriage of the tub far enough on it's adjusting screws to accommodate a decent sized timber without raising the bath.

 

[joe-90]

Why do any of it in the first place? If your joists are rotten - then replace them.

 

[securespark]

HR: Joists seem fine. Their size is OK and they are not rotten.

The new bath is 1800 x 800 as opposed to 1680 x 700, so not like I'm putting in a communal bath , however it does hold a bit more in litreage.

The new bath is here:

http://www.bathstore.com/products/wash-acrylic-bath-1800-x-800-1415.html

 

[jabuzzard]

Like I said 18mm sheet material is going to do nothing to spread the load. Lengths of timber joist will do far more to spread the load. Just make sure they rest over the floor joists.

My personal top tip for fitting a bath is before you fit the side panel stuff the void up with some loft insulation. I went for the stuff made out of recycled plastic bottles as it is none ichy. Does two things, firstly it keeps the water hotter longer when you decide to have a soak. Second it makes the bath quieter. Given the stuff is subsidized it is really cheap to do as well, at least a lot cheaper than the "insulated" baths you can buy.

 

[maltaron]

cant understand why you are worried. Cast iron baths were the norm not long ago and I have never known one going thro' the floor.

 

[jabuzzard]

cant understand why you are worried. Cast iron baths were the norm not long ago and I have never known one going thro' the floor.

The weight of the water of a filled bath far exceeds the weight of a cast iron bath. I suspect that he is concerned because the bath he as is some what bigger than the normal, though not massively so.

 

[foxhole]

4X2 bearers laid across the joists (in line with the floorboards) will do more to spread the load than a flat sheet of ply.
It's usually possible to wind up the undercarriage of the tub far enough on it's adjusting screws to accommodate a decent sized timber without raising the bath.

I agree, sheet timber is not spreading the load.