Chipboard floor squeaking - no screws/nails visible

Discussion in 'Carpenters' Talk' started by Bennywidag, Sep 21, 2021.

  1. Bennywidag

    Bennywidag New Member

    Hi all, first post I hope this is ok, I have recently bought a house, built in 1984 as a council house and lived in then owned by my seller since then.

    The flooring throughout the house is squeaky upstairs and down, I am in the process of ripping up the carpets in the hall and dining room to replace with engineered wood flooring and my intention was to address the squeaking as best I could during this, by screwing alongside existing nails or whatever technique.

    However as you will see in the images the chipboard sub-flooring has no visible nail or screw marks, and i have gone around with a magnet to make sure I'm not insane, from the (small) smudges on the joints i presume it has been glued down only and the joints seem to move and squeak when you stand either side and apply pressure so maybe in places it has de-bonded.

    Has anyone had experience with a floor like this (ie without fixings) and how would I best go about improving it, ideally without replacing the lot which has come to mind!
     

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  2. Bob256

    Bob256 Member

    I have heard of boards being laid directly over a layer of insulation. Perhaps that's what you have? I am not sure what the remedy would be for the squeaking though.
     
  3. Bennywidag

    Bennywidag New Member

    Yes I have seen similar too, a floating floor of sorts over the insulation. I really don't think its that given the type of house and that it hasn't been renovated in that sort of way but I think I am going to have to lift one of the boards to look.

    If it was that I guess the only remedy would be more glue as the noise is coming from the joints, but I don't think that is my situation.
     
  4. Abrickie

    Abrickie Screwfix Select

    FWIW it’s completely possible that a house of that age was originally built with a floating floor
     
  5. pppmacca43

    pppmacca43 Super Member

    I think u can brush/pour watered down pva into the joints to help stop the squeaking, not done myself but remember someone telling me about it.
     
  6. GrahamTaylor

    GrahamTaylor Member

    If you suspect that it is a floating floor on top of insulation you should check before you do anything drastic. Find an inconspicuous area away from likely traffic, use a metal detector to make sure there are no pipes or cables underneath and use a 25 spade bit to drill a hole through. Once it does through the board you'll be able to tell whether it has hit a void or insulation material.

    If you have got underfloor heating DON'T DO THIS!

    Most likely is that you'll find a rigid insulation board (Kingspan or similar) underneath. If it is the floor is likely to be floating which means that the boards are just held together by glue in the Tongue and Groove joints. Modern glues are very good but older ones are often a bit dodgy and sometimes were not used at all. This will allow the joint to move a little and you get the noise from rubbing of the tongue in the groove.

    Two ways to address this involving more glue.

    First way is to water down PVA type glue until it is really runny and then brush it liberally onto any squeaky joint area and keep on working it in so that it absorbs into the crack of the joint. Anywhere that seems to absorb a bit you should brush in more. Leave it to dry overnight and then use a floor scraper to take off the mess you've left.

    Second way is the use PU adhesive. Pick a noisy joint and mark a line about 25mm from the joint edge on either side. Drill a hole about 15 deep into the board on the line. On one side you will feel the drill will break into the gap left between the tip of the tongue and the back of the groove. You may need to do quite a few experimental holes to find it. You will need to do this on both a long side and a short end but then you will know the orientation of all the boards and the correct distance in to drill the hole. Now drill holes like this anywhere that is squeaky but do not drill all the way through the boards. Now use a smaller plant sprayer to wet the inside of the holes. Then use PU glue (40778 from our hosts) and inject it into every hole you've drilled. In contact with the water this will foam and expand along the joint filling, sealing any cavity. Leave overnight and then use a scraper to remove the mess (there will be a lot of it!).

    The PVA method is cheaper but I find the PU method can cope with more serious cases and is good if the squeaks are more localised. Neither method is guaranteed to be 100% but I have managed to make big improvements to floors that have squeaked for years that have been driving the customer to distraction.
     
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  7. Bennywidag

    Bennywidag New Member

    Thank you massively Graham, I really appreciate it. As it turns out I went over last night to investigate more and didn't see your message until now.

    I used a stud finder and couldn't find anything at all under the floor. At the joint of the sub-floor and the front door the floor dipped by 5-6mm, was sealed to the door frame and I was planning to shim this before installing my floor. On further inspection the bit of floor moved when pressed and didn't seem secure, it had evidence of previous nails but none present, so I took out a small bit of skirting that allowed (with some hacking and swearing) it to be removed with no evidence of glue at all, and it seems to be 20mm thick rather than 18 or 22.

    Underneath was as all of you predicted, floating floor on top of a layer of polystyrene insulation (image 11), around 30mm thick but I forgot to measure. Whilst initially I thought there was some timber support it was just a load of rubble and scrap wood shoved into what I believe is essentially a continuation of the cavity of the wall. So there was nothing apart from the insulation on top of brick with some kind of vapour barrier inbetween, then rubble pile, holding the floor up (image 13 & 17). In addition the door frame (which I felt was soft before) sits on top of a 20mm thick layer of expanding foam thats on top of the bricks, no support at all in there apart from a random wedge or two at the ends (image 15). The 20mm long screws just spin in the foam obviously.

    I have cleared out the bit of cavity wall (image 18). My plan is to screw a piece of 1.75" square C16 timber to the brickwork at the right height for either the sub-floor or with insulation inbetween. Probably replace that bit of insulation I cut out with PIR, and repair the vapour barrier. Wedge some blocks of 20mm wood at points ~150mm along the door frame without loading the frame and put new screws through that into the brick, and seal around this with expanding foam. Screw the sub floor down to the C16 to allow removal for any reason. Does that all sound ok?

    As it was clear its a floating floor I decided PVA was the only way to address it. I watered down PVA (57248) at ~3:1 as that's what I had seen on Skillbuilder, I wasn't happy that it was the correct viscosity (was ~skimmed milk) so I added a bit more PVA to probably 2.5:1 or maybe 2:1 and it was more what I had seen, a bit thicker than whole milk, less than single cream (sorry about the analogy). It seemed to be right, was very easily brushed in, would absorb leaving open cracks to refill so I don't think that was too thick.

    I did this in the dining room which wasn't as bad squeaking for a first try, I will use your PU method on the bad spots in the hallway thank you so much Graham. I don't want to touch the floor I'm putting on top of this so very keen to sort this as best as I can. Sorry for the essay.
     

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    Last edited: Sep 23, 2021

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