reinforcing small area of floating chipboard floor in closet

[dalahorse]

Hi

I'm trying to figure out whether there are any options to create a more solid base for a washer/dryer unit located in a small closet (roughly 75cm W X 95cm D) in my kitchen (ground floor) in a 1986 Barrat terraced house.

The closet previously housed an immersion tank (removed when converted to wall hung condensing boiler). I had my washer/dryer moved into the closet to create more kitchen space for a dishwasher. However, the tongue and groove chipboard sub floor in the closet had deteriorated and warped (from water damage) so I figured I would need to replace/strengthen the floor to provide a level surface for the washer. The washer worked OK but was prone to rocking/imbalances even when completely level.

I recently had a builder investigate and we both incorrectly assumed there were joists under the floor (probably because we heard hollow sounds from the few voids for water and gas pipes underneath). However, after carefully removing the chipboard in the closet, he realised it (and the rest of the kitchen sub floor) was floating tongue and groove chipboard over polystyrene insulation block on a concrete solid floor with service pipes sitting in the insulation.

While acknowledging it might not work that well, the builder suggested replacing the removed floor with heavy ply (3/4" I believe) and fixing it to the concrete below (through the insulation) avoiding any service pipes. He then put another layer of ply on top of that and fixed it again. However, as I expected, the washing machine (even though completely level) becomes unbalanced at higher spins due to the natural movement of the insulation underneath. In fact, it's probably worse than before because the load is not being distributed across the whole floating kitchen floor (basically just sitting against the back and side walls of the closet). We fixed some L brackets from the ply floor to the bottom of the door frame to stabilise but didn't make much difference.

So, I'm wondering if I have any options to construct something more solid in the closet to support the machine. Raising the floor higher than the rest of the kitchen would not be a problem because it's hidden behind a closet door. A few things I've been mulling:

1) Creating some sort of concrete base just in the closet (on top of the existing concrete/insulation). However there are water pipes running diagonally across the closet so would guess would require a conduit. Possible or workable?

2) Removing some of the insulation and fixing some sort of wood or metal battens to the concrete screed beneath to create a raised platform and mounting ply or similar onto that.

Any other options anyone can think of?

Thanks

 

[StephenW]

What are the side walls and back wall made of? If appropriate, you could build a timber framework out of 75x25 fixed to the sides and back, with intermediate cross-pieces and then a ply floor on that.

 

[dalahorse]

Thanks--the back wall is the party wall (block cavity wall), left side wall also blockwork. Right side wall is just stud partition. However, there is some pipework running out of the back and left side wall (as this was originally the boiler closet)

 

[big-all]

remove the flooring see if you could give extra support to the floor by legs down to terra firma

 

[dalahorse]

thanks big-all, when you say remove the flooring do you mean the insulation and concrete screed? The chipboard sub floor has already been removed and we fixed the ply over the insulation down into the concrete base.

 

[big-all]

sorry have now fully read your post

go for mass 25mm ply will be very reluctant to flex where as 12mm will easily spring
indeed i would go as far as saying a further 12mm bit off ply glued and screwed to the 25mm may give you enough "rigidity" to stop the problem
plus you need to tie the rest off the floor to the new bit otherwise its just going to bounce alone

 

[dalahorse]

Thanks for the help. Anyone else have any suggestions? Is there a more rigid insulation I could use under the ply?

 

[big-all]

could you force some 6mm ply around the edge between the insulation and floor

i have done this in the past with pvu foaming glue and it held well in a bathroom for several years but suspect this challenge may be more dificult

do you have any pictures off the area

 

[dalahorse]

Big-all, thanks again. Possibly, could attempt the ply around the edges, might have some issues with service pipes running underneath. Will try to post a picture later today-- washing machine fits in pretty snugly in closet so hard to get a clear photo of the floor area.