Replace rotted subfloor

Discussion in 'Plumbers' Talk' started by Coaster, Jun 30, 2021.

  1. Coaster

    Coaster Member

    The laminiates in the kitchen has been removed and the subfloor has a top layer of chip board is now very soft and crumbles / rotted and undernealth is polysterne insulation and then concerete floor.

    Also, the bathroom floor the mdf has weakened or rotten due to leak from toilet and sink and also underneath the front of the bath tub

    I am looking to have the floor repair and lay vinyl on top. What would be a practical way to make the subfloor water resistant / proof ? what material to use? for each of the area?

    What tradesman should I look for do this work ?
  2. kiaora

    kiaora Guest

    the answer is, imho.
    experienced builder to lay a new floating floor
    good luck
  3. Dave1988

    Dave1988 Member


    Peter replied to me too lol hi Pete

    Sounds like you got the same floor as me! No joists just floating sheets t and g. This stuff is a nightmare to get level your best but is to cut out the damaged. Replace with same thickness thickness overlay the room with 6mm ply and then your vinyl.

    If its a high traffic area use adhesive all over for sheet vinyl as well as double sided tape around perimeter
  4. Coaster

    Coaster Member

    Almost all of the subfloor had rotted (left it over a month to dry ) so I guess best to uplift and replace. I was told as it is cement underneath the subfloor the joist should be fine. Is this correct?
    How long will it take to uplift and make good of the floor ? 10ft 2 x 5ft5 inches and there are 3 kitchen unit

    apart from checkatrade, ratedpeople, mybuilder.. where is a good place to look for tradesman for this work?
  5. Danny32

    Danny32 Member

    I had the same problem with water damaged bathroom subfloor which was 18mm T&G chipboard. Loo had been leaking for years before I bought the property and the floor had swelled.
    I’m doing a ground up refurb and have bought four green grade moisture resistant 18mm T&G chipboard boards from Wickes.
    On top of that will go Aquastep waterproof click flooring with a suitable membrane.
  6. Coaster

    Coaster Member

    Danny32 shame you are in a similar situation.

    I was told the water resistant board is not suitable for flooring, is that true?? and also not to use chipboard but I think as long as the areas are water tight they should not be a problem? I am now changing back to mdf / plywood instead of using the water resistant board as it is dearer.
  7. Danny32

    Danny32 Member

    The water resistant board is flooring.
    It’s cheap, T&G unlike ply and better than the basic non water resistant stuff that was there before.
    It had carpet on it previously and the chipboard had swollen through years of water leaking through.
    Marine ply was also suggested.

    I figure that with waterproof flooring on top and all new suite and pipes, it should be ok.
  8. Coaster

    Coaster Member

    Good to know about the flooring materials, Danny.
    I wanted to check, if the stop cock has been turned off and the cold water runs off the water tank. And there are drips from the water pipe when the cold water is in use (see leak.jpeg) can this be fixed by sealing the pipe? if so, how? As I am hoping to get the subflooring complete and the kitchen reinstalled then sort out this leak problem after (and leave the stop cock off and not use the warter) will this work ??

    Attached Files:

  9. Bob Rathbone

    Bob Rathbone Screwfix Select

    I would not use chipboard under the pan in my own house. If you have kids, boys, then they will invariably miss the target on occasions and over time moisture will build up. I use a piece of ply about 300mm bigger than the pan footprint, then I can be sure that in the event of moisture, either from misses or cleaning, the floor will survive and the pan remain stable.
  10. ElecCEng

    ElecCEng Screwfix Select

    The standard is P5 chipboard floor. ‘Moisture resistant’ is available but isn’t ‘waterproof’. If you’re using vinyl then that’s waterproof and properly sealing around the base of pedestals pans bath etc with quality sealant you shouldn’t have any problems. As Bob suggests you could gold plate it with some ply over the top. The issue you’ve found is more to do with the fact that the carpet isn’t waterproof than what the floor is made of, although MDF was not a good choice by whoever put it in…

    Anywhere you have a joint should be ideally be accessible so you can check for leaks.

    Allegedly there is an industry wide shortage of P5 at the moment…

    The arrow in your picture points to a waste pipe into a boss in your soil stack. If that is leaking you need to check the joint. If it’s push fit then check the size of the waste is correct and the washer in the boss is in good condition. If it’s solvent weld you may get away with sealing a pinhole with some solvent or silicone but otherwise replace the boss.

    Looks like there are a couple of drips on your capped copper pipes. These could be from the push fit caps or bad joints on the elbows. Dry the drips and then check back regularly to see where they are appearing from.
  11. Danny32

    Danny32 Member

    This is the board I bought from Wickes. Had them delivered as they’re 2.4m long.

    Attached Files:

  12. Coaster

    Coaster Member

    Excellent, Danny!! I am hoping I will get floor done tomorrow!!

    Bob & Elec - thanks for your replies, I will check the joint and then seal it, what would be a good material to seal? or if I need to replace the pipe and boss what should I buy?
    Can I still have the subfloor install ? as I hope by sealing the pipes will stop the leak. As it not easy to find a tradesman to come and look at short notice.
  13. Coaster

    Coaster Member

    Hi, the soil pipe has been sealed with CT1. but still leaks..see CT1 a suitable product to seal?? Can the seal could be done differently? Also, will cutting part of the pipe out so that the pipe (in the photo) can be fitted around the leak and add back the cut out pipe will fix the leak??
    Excuse the many questions,.. hoping to know more about the fixes. Cheers

    Attached Files:

  14. pppmacca43

    pppmacca43 Screwfix Select

    CT1 is a good sealant and will often seal up non pressurised leaks on soil pipes but with respect it looks a right mess what u have done there With the sealant. U need to put it on then smooth it off, looks like it has just been thrown on. Best thing to do would be cut out and replace the pipe tbh.
  15. Coaster

    Coaster Member

    Do you mean even if it is sealed properly it may still leak? How do you cut the pipe and seal the joint? These are the two access to the pipes one is from the bathroom floor to the kitchen ceiling getting to limited access to where the leak is the second access is from the top of the kitchen wall, next to the pipe. Is it necessary to knock down all the walls to replace the pipe?

    Attached Files:

  16. Coaster

    Coaster Member

    Update, regarding replacing the soil pipe. I need some help to check the quote includes all the work that needs to be done, please.
    I was told they will cut the 'walls' that box the pipe in the kitchen and bathroom, then replace the soil pipe and also the pipes that connects to the washer, kitchen sink, etc.. I wanted to check this is included in the quote. also, is there a way to know how many hours does this type of job usually take? The quote is attached (including other tasks but I am thinking I can get a handy man to do panel, sealant etc) and it is (London) fixed price of £1152 incl vat. There hourly rate is £96 incl vat. Any thoughts much appreicated.

    Attached Files:

  17. qwas123

    qwas123 Screwfix Select

    The quote doesn't include all the work thats needed or the work you say was "mentioned"

    Mate, you want to stop and step back and work out exactly what you want your b/room & kitchen to end up looking like. At the moment since june 30th you've been all over the place.
    Whats happened to the kitchen floor in the latest scheme of things?

    What you can afford i dont know but heres what i'd suggest if i was theguy coming in to give a quote.
    Clear all fixtures (except the bath) from the b/r.
    Remove all boxing and skirtings and cut out & lift the rotted b/r & kitchen floor. Replace with ply or chipboard. Concrete kitchen floor might only need SLC over the concrete.
    Take the c/w water from the mains pressure riser. Remove the loft CWST unless its still needed?
    Sort out all your supplies - c/w on RH and h/w on LH.
    Sort out the waste and soil pipes. - use boss pipe fittings not strap fittings for connecting wastes.
    Think about a new WC - no need to raise it with a new stack.
    Make good to all disturbed areas.

    Sheet vinyl spread over the floor & flopped up the walls/abutments will seal against leaks.
    Fixtures will then go on top of the one-piece vinyl sheet.
  18. Coaster

    Coaster Member

    thanks for all the helpful replies!!
    qwas123 - I agree with you as I am still finding out the basics!
    The kitchen and bathroom floor are clear and ready to go, hoping to use a carpenter and plumber to do the followings:
    - replace the soil pipe (unfortunately, was told by many it can be repaired!)
    - replace the toilet
    - replace the subfloor in the bathroom and kitchen
    - rebox the pipe in kitchen and bathroom
    - fit vinyl in one sheet under all unit - (any cons in doing it all in one sheet? as I cannot see any cons)
    - refit back kitchen
    - refit back bathroom
    - seal all areas
    Any comments welcome

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