Levelling Joists -methods?

[KillingTime]

Hi,

Got my floor up at the moment in the bathroom.

I'm hoping to make a 'wet area' with tanking and wediboard. I've been reading the wediboard site, and their step guide requests that you make sure your joists are level prior to fixing the wedi floor.
Well, I've checked my joists and they are not level. All the joists seem to be at different heights. The biggest gap is about 4mm. This may not sound alot, but where the floor is to be tanked, it will surely bend and flex under my weight, which will cause the tiles to come up prematurely.

My question is, what's the best way to fill the gaps between one joist and the next?

I read on one site that the only way to do this properly is to fix another joist to the bent one with bolts. Sounds like alot of hassle.

I could use wood shavings, but these will come loose over time and drop out.

What about layers of 'builders (metal) band' ?

Is there anything thick enough (like mortar) that I can level out on the joists that will set very hard? I've heard some people suggest dry wall adhesive as an option..

Thanks.

 

[IJWS15]

I would glue/tack on plastic window packers onto the joists - a bag of 200 @1mm will be about a fiver and will give you all the adjustment you need. Set with a level/long straight edge before you board it.

If the joists give as you stand on them you have another problem.

 

[^woody^]

Seems like a complete waste of time to me.

4 mm is insignificant over the whole area of a bathroom floor. You can just lay new boarding (ply or hardboard) over the top if required, which will give a flush surface to recieve the flooring.

Floor boarding does not 'bend under the weight' to any significant degree.

 

[ModernMaterials]

As you have just been saved the cost of duplicating all your joists, i would suggest no less than 5mm marine ply, glued down with gripfill and screwed to the joists and carefully levelled under your showerstall using timber or plastic spacers.

Dont bother skimping with hardboard when you are spending so much on the rest of the job.

 

[ColJack]

seing as you are going to tank it and have a shower on top then why not just use self leveling stuff on it to fill the dips... ?

BTW, i'm an electrician and have no knowledge of the mysterious ways of the builder...

 

[bernardgreen]

seing as you are going to tank it and have a shower on top then why not just use self leveling stuff on it to fill the dips... ?

BTW, i'm an electrician and have no knowledge of the mysterious ways of the builder...

Self leveling is great, if you want a level floor. I cannot reccomend it highly enough.

But it sticks like glue to anything it sets on and defies removal even from stainless steel shower trays.

And if you need a slight slope on the floor to ensure water runs into the drain area forget self leveling.

 

[anobium]

Lay a straight edge on top of the joists and then bring them up to required level of straight edge using timber or plastic wedges from the underside.
Nail the wedges to the joists on completion.

 

[KillingTime]

Thanks guys.

I'm not sure raising the joists from the underside will work as half my landing is resting on them at the moment (I need to leave at least some part of the house to live in....).

I will try the plastic frame packers to start with, and if the finished product is still not up to scratch, SLC.

 

[marksson]

Self levelling can be laid to a fall but knock it up a bit thicker.

 

[ColJack]

doesn't need it with a fall.. the wedi board will do that for him..