bath drops about 5mm when full

[weird_dave]

I'm doing up my bathroom, replaced a load of floorboards under the bath due to woodworm, treated the new wood and the joists (which did have a small amount of worm damage).
The joists did seem to have some sideways movement but was told this shouldn't be a problem once the floorboards were in. I predrilled holes and screwed the floorboards down to every beam.
I attached the bath to some 2x4 so it's effectively on 2 big fat skis, i've not attachedit to the wall yet.
Filling it seems to make the bath drop a little, I marked the wall before and after filling. After emptying the first time, it didn't quite reach its original height. filling again and it drops to where it dropped before.
Will this be a big problem? When I attach to the wall, this may reduce the issue at the back of the bath. Should I attach extra brackets?

Thanks in advance for any thoughts

Dave

 

[mogget]

5mm is a long way for a bath to drop when full, especially as it's on reinforced mountings.

How are the joists fixed to the walls they join, and is there any movement there when the bath is filled?

 

[weird_dave]

It's difficult to tell, but I couldn't see any when I pushed with a long piece of wood.
The joists go into a gap in the wall and just sit there.
It's actually 5mm lower at the wall where the joist sits in the wall.
The bath is 170cm long with the legs at 49cm from the end. It's a center tap/plug setup (Valencia suite from B & Q). Just checked the instructions and it says the legs should be 46cm from the end, oops.
I just setup a laser pointer from another room to point to the 2x4 one of the legs is on (the one nearest the joist end wall) and emptied the bath. It raised approx 2mm but about 4.5 on the wall. I guess it's possible the whole top floor moves, but I don't think it's so likely!

 

[dextrous]

If the joists had lateral movement, then it's always possible that any mortar beneath them has crumbled to and that there is minor droppage taking place as the bath weight varies.

Three solutions spring to mind -
1/. Live with it, but consider attaching timbers to the wall on the underside of the rims to prevent it dropping and splitting the silicon
2/. Instead of timber supports under the legs, use full length L irons, which are not prone to flexing
3/. Lift floorboards and wedge joists in with timber wedges and/or mortar to minimise any movement.

 

[weird_dave]

1: I was considering a bunch of shelf type brackets to support the rim on 2 walls, does this seem reasonable?

2: I'm really going off wood. I feel like replacing all the joists with metal! This house is a nightmare....

3: My worry is that this doesn't solve it and the joists are just knackered and need replacing. I'd hate to have to take it up again to replace the joists.

I forgot to mention which way my 2x4 skis were aligned, they are widthways rather than lengthways. The idea was to reduce/eliminate flex in the floorboards by spreading the force over the beams more rather than have the weight in one spot between beams.

Your input is greatly appreciated, given me food for thought.

Now to go check if I've fixed that blasted leak.....

Dave

 

[mogget]

I don't quite understand what you mean about the orientation of the ski's. They should sit on the joists, ie they should run the same way as the floorboards.

Its important that the ends of the joists do not move up and down relative to the wall they are inserted into.

 

[weird_dave]

I screwed the bath legs to 2x4 which are resting on top of the floorboards. the 2x4 are the skis. They can't go directly on top of the joists due to the position of them, the 2x4 would have to come out too far.
It's times like this I wish I had a camera....
I shall try to give more detail:
The bath is in a corner above joists running lengthways to it. Floorboards running widthways. I mounted the legs on top of 2x4, widthways also.
While the floorboards were up, I did bounce around on the joists trying to spot vertical movement, but it's very difficult to do that alone.
There's a chance I may be able to laser tag the joist if I can find the right angles from a fixed position in another room, then see what the water weight does to the end of it.

At least the bath is currently working and hasn't fallen through

Dave

 

[Axel]

Alternatively, never empty the bath. Only remove plug while it is being re-plenished with hot water. It will probably be in a constant state of soapy dirty water, but apparently there's a soup in China they've kept going for 800 years, adding more ingredients every time some is served......

 

[dextrous]

I screwed the bath legs to 2x4 which are resting on top of the floorboards. the 2x4 are the skis. They can't go directly on top of the joists due to the position of them, the 2x4 would have to come out too far.
It's times like this I wish I had a camera....
I shall try to give more detail:
The bath is in a corner above joists running lengthways to it. Floorboards running widthways. I mounted the legs on top of 2x4, widthways also.

So the skis do not traverse the whole width of the room. Approximately how many joists do they cross over? It may help if the skis are screwed through to the joists.

 

[weird_dave]

I'm liking the soup idea...

The skis can't traverse the room, I'd have wooden bumps in the floor!
They traverse 2 joists. They are not yet screwed down and the bath isn't yet screwed to the wall, but I don't actually think that will make a huge difference.
It'll be a while before I need to actually secure everything in place, plenty of time to pick peoples brains and mull everything over

I appreciate all the feedback.

Dave

 

[dextrous]

Screwing the bath to the wall will make a difference, however. As it's not all fixed in place, would recommend you lifting the boards and ensuring joists are firmly wedged. Add noggins where you can (it all helps), and screw skis through to the joists. Beyond that, there's little else you can do.

 

[weird_dave]

I'll screw the bath to the wall (I can see the bracket may slide on the screw head if there's enough force though).
I assume noggins are struts between joists? (I had to google...)
Not too sure how to add them, is there a guide? I tried to google but my DIY vocab is way behind my googling skills.

Dave

 

[dextrous]

Measure between the joists and cut some timbers (2 by 2, 3 by 2 or some of that spare 4 by 2), wedge into place and use screws angled in to hold them firm. These should add to the rigidity of the joists, which is what we're trying to achieve by the sound of it.

The bracket that goes into the wall is not going to slip anywhere by the time it's covered with plaster or tile adhesive. I'd recommend you scrape a bit of plaster way from bhind the brackets so they don't stand proud of the wall while also allowing for an extra bed of tile adhesive.

 

[weird_dave]

I've taken the plaster away for the brackets, they will screw directly into brick. I'll try it tonight and see what happens.

Thanks,

Dave.

 

[BingoBongo]

can u post a pic

if its dropping when full whats it going to do when you get in?