Replacing "weetabix" sodden chipboard floor in kit Help, advice, information, answers and tips on all types of flooring from laminate and carpet to timber and vinyl

[The Riviera Kid]

Hi folks,

A couple of months ago when pulling up the horrid floor covering in our kitchen I noticed that the floor was somewhat "bouncy" around and under a unit. When the floor covering was pulled up and the unit removed, it appears that some bad plumbling has been leaking down the wall and creeping under the floor, turning an entire section of the floor into a mushy wet weetabix like substance - which crumbled to bits in my hands. Under the crumbling section of chipboard I found a polystyrene insulation block covered by a blue plastic membrane sheet. Under this is what appears to be a floor consisting of solid concrete blocks.

I'm left with a bit of a dilema, as the kitchen floor itself is a bit of a mess. It's largely uneven with different thicknesses of chipboard, bumps, humps and slopes, gaps and warped sections. Should I simply replace the knackered section and be left with a functional but largely unsatisfactory job, or should I rip the whole lot up and start from scratch? (gulp).

Some questions that might help me make up my mind.

1) While I appreciate nobody here is psychic lol, what am I likely to find? Will there likely be a framework, or is it possible that the chipboard could just "float" on the polystyrene blocks? There doesn't appear to be any framework around the edges where the knackered section has been pulled up.

2) If I remove the whole lot, will any insulation need to go down first, or could I simply level the concrete floor a little (with a self levelling compound) and put down something like a 18mm plywood? Would this need to be on a framework or could it be layed directly on top of the concrete?

3) if the floors coming up, I'm thinking it might be an idea to partition a section of kitchen off, as we'd like a walk in closet. I'm guessing it would be best to partition this before laying the plywood?

My apologies if this all sounds a bit mad. To give you some background, I'm competant at basic DIY and woodworking, but haven't a clue about the insulation/damproofing side of things. I'm confident I can get the woodworking side of things spot on, but don't want to do anything crazy that will result in a cold or damp kitchen.

Oh and the kitchen is 5m x 4m

Cheers

[stoneyboy]

The Riviera Kid,
Lift the existing chipboard, leave the dpm and insulation in place, fit new tempered T&G chipboard and glue the joints. If the closet wall is not going to be load-bearing build the closet wall direct on the chipboard.
end

[rosebery]

What flooring do you intend using as a finish? Vinyl or ceramic or something else?

[The Riviera Kid]

So sorry for taking so long to reply. I'm unsure on finish yet, it really depends on the cost. As the biggest hump in the floor is 1.5in higher than the level parts of the floor I'm fairly resigned to having to bring it all up....

...but...do I level it and re-lay the polystyrene followed by a new chipboard or plywood, then a laminate to finish, or should I just lay some new slate or ceramic tiles on the newly leveled concrete?

If I went for the second option, do I lay the tiles direct onto the stone/concrete, or does any sort of liner/base need to go down? Also, what happens to the air bricks which are currently below skirting board level, but which presumably be at about skirting level if tiles were laid direct?

[rosebery]

"So sorry for taking so long to reply. I'm unsure on finish yet, it really depends on the cost. As the biggest hump in the floor is 1.5in higher than the level parts of the floor I'm fairly resigned to having to bring it all up...."

I think thats the best idea.


"...but...do I level it and re-lay the polystyrene followed by a new chipboard or plywood, then a laminate to finish, or should I just lay some new slate or ceramic tiles on the newly leveled concrete?"

If you are going to use ceramic tiles it really needs to be 25 mm ply. If vinyl flooring of some description then you can get away with chipboard as a sub-base but I'd lay 6mm ply over the top before the floor - particularly if its going to be Karndean or Amtico. But see below as well.


"If I went for the second option, do I lay the tiles direct onto the stone/concrete, or does any sort of liner/base need to go down?

You could having used a levelling compound but see below.


"Also, what happens to the air bricks which are currently below skirting board level, but which presumably be at about skirting level if tiles were laid direct?"

Opps thats the b..lbuster!! Airbricks are to provide subfloor ventilation and should not be above the floor.

Depending on relative heights it would seem sensible to me to consider installing joists laid parallel to the airbricks (so that the air circulates between them). Doing this should make it relatively easy to avoid the major ups and downs of the concrete and avoid having to level it. You can then screw ply directly to these giving yourself a perfectly flat surface for tiling or whatever.

You have to be careful about relative levels though.

HTH

Cheers

[The Riviera Kid]

Thanks so much for the advice. I suspect I'll be back for more soon lol.

Got some less intensive stuff to do around the house before we look at the floor coming up - watch this space :)

[The Riviera Kid]

Well....I've priced up a rough cost for the joists and new chipboard (it's shocking how warped and "hilly" the old stuff is now that I've taken a real close look), and I've enlisted the help of a competant friend, and booked in the 29th March as the day we rip it all up and lay the new floor - as I really want it useable in one day (compact house, wife and four kids). Like I mentioned previously I/we are reasonably competant on the woodworking side, but are a bit patchy on the concepts of sub floor ventilation and damp proofing....so....

....currently it's stone/concrete, followed by polystyrene blocks, followed by a large blue DMP covering what appears to be the entire floor, followed by the chipboard.....

...so if I lay joists (whether it be "negotiating the bumps" somehow, or after levelling), I'm guessing the polystyrene blocks could be cut to fit in between the joists, but what happens to the DMP? Should it be laid on the concrete before the joists, or some other method?

Thanks in advance folks. :D

[The Riviera Kid]

*** Opps thats the b..lbuster!! Airbricks are to provide subfloor ventilation and should not be above the floor. ***


As I'm keen to learn (and so it's an option, once the floor is ripped up), might I be right in taking a guess that if the airbricks are either removed or blocked up, that once the floor is levelled - ceramic tiles could be laid direct onto the stone?

[rosebery]

You need a flat surface to install ceramic tiles. Do not attempt to put ceramic tiles down on chipboard. They will lift sooner or later even if you use a decoupling membrane. If you are going to go for the joist approach to bring the floor level then use minimum 18mm ply and prime it first with something like BAL APD which is an acrylic primer. Do not under any circumstances use PVA to prime.

DPM under the joists and cut the insulation blocks to fit between the joists.

Oh and yes you can lay ceramic direct onto a stone substrate if its suitably flat. Use a proper flexible adhesive (bagged not the tubbed stuff from the sheds) for either ply or stone.

HTH

Cheers

[The Riviera Kid]

Thanks for the advice, I think I'm starting to understand the concepts involved now! :D