Preference for screws to fix 9mm ply to 22mm chipboard?

Discussion in 'Wood / Woodwork / Carpentry' started by Milleniumaire, 29 Oct 2020.

  1. Milleniumaire

    Milleniumaire

    Joined:
    7 Jan 2010
    Messages:
    616
    Thanks Received:
    6
    Location:
    Yorkshire
    Country:
    United Kingdom
    My Omnie TorFloor UFH is now in place and has been filled with water at mains pressure with no leaks, so after the pressure test tomorrow I'm ready to overlay the 22mm chipboard with 9mm ply, which will be glued and screwed.

    I know fixing plyboard over UFH isn't a great idea but it is required as part of the Omnie specification to ensure the floor has the required structural integrity.

    It occurred to me I haven't yet purchased any screws and was thinking of getting the Screw-Tite 2 PZ Double Self-Countersunk Screws 3.5 x 25mm or possibly the 4 x 25mm from screwfix.

    The combined floor thickness will be 31mm, so don't want to risk 30mm as these may push through the chipboard. 25mm seems safe.

    Are there better screws or will these do the job? I suspect there's not really anything between the 3.5 and 4 sizes?

    Sorry, I'm probably overthinking this, but just want to be sure I'm not missing something.


     
  2. Sponsored Links
  3. SFK

    SFK

    Joined:
    23 Jul 2010
    Messages:
    2,030
    Thanks Received:
    474
    Location:
    Oxfordshire
    Country:
    United Kingdom
    I like these screws and found them good at pulling ply sheets tight onto joists.
    Would suggest X 4mm as wider head more likely to stop screw going too deep and more purchase for screwdriver bit.

    BUT .... You are getting short 25mm screws (which I have never used as mine were longer) did you see the following issue with 25mm screws on screwfix website?:


    Jul 2020
    By Muttley59
    Wiltshire
    " Purchased box of 25mm screws, but screws in the box not as shown on website, or as pictured on box. Contents were a standard 25mm screw with none of the features shown for this 'Next generation screw type'.Exchanged for standard screw at less than half the price. Staff at store not very helpful, suggesting that the special features were probably absent because the couldn't be fitted in on the short 25mm length. Don't know if this is result of wrongly packaged screws or the 25mm versions don't have the features, if the latter then it should indicate this clearly on the website. "

    0 of 2 people found this review helpful.
    Was this review helpful?YesNo(Report Review)

    Screw-Tite Product Expert20 Jul 2020
    Thank you for your review. As stated on the box, the Dowel section of the screw, Ream and Tite are not available on screws under 30mm in length, in the same way that smaller sizes of screw do not include the part threading. Unfortunately due to the length, it would be impossible to fit all of this onto a smaller size, in addition, these features would be ineffective on smaller lengths. However, the screws still feature all the additional features to put them above the 'standard screws' including the Stick-Tite recess, Tri-Lock shaft and TS thread form.
     
    Last edited: 29 Oct 2020
  4. Milleniumaire

    Milleniumaire

    Joined:
    7 Jan 2010
    Messages:
    616
    Thanks Received:
    6
    Location:
    Yorkshire
    Country:
    United Kingdom
    Yes I did see that review and can understand why the shorter screws might be different, but shame on screwfix for not showing the correct image.

    As long as they are not threaded all the way upto the head then they should pull the plywood tight.
     
  5. JobAndKnock

    JobAndKnock

    Joined:
    30 Sep 2011
    Messages:
    6,839
    Thanks Received:
    1,483
    Location:
    Lancashire
    Country:
    United Kingdom
    For the task at hand you want 4.0mm screws not 3.5mm ones because the heads are larger. There is no intermediate size unless you get drywalls where some manufacturers do a 3.8mm screw. When driving all threaded screws like this you need to ensure that your screwdriver is running sufficiently fast and that you apply enough pressure to flush the screw heads.
     
    Last edited: 30 Oct 2020
  6. Milleniumaire

    Milleniumaire

    Joined:
    7 Jan 2010
    Messages:
    616
    Thanks Received:
    6
    Location:
    Yorkshire
    Country:
    United Kingdom
    I'm guessing at 25mm long, none of these screws have a "dowel" i.e. lack of thread just under the head, to ensure the board being fixed (9mm ply in my case) is pulled tight?

    screwfix do show a Goldscrew Plus PZ Double-Countersunk screw (4 x 25mm), with an image that does suggest there is a dowel, however the image also shows a much longer version than the 25mm (just like the Screw-Tite 2 PZ images).
     
  7. Sponsored Links
  8. SFK

    SFK

    Joined:
    23 Jul 2010
    Messages:
    2,030
    Thanks Received:
    474
    Location:
    Oxfordshire
    Country:
    United Kingdom
    Those are my go to screws (cheap and not too sharp).
    Sorry, but Thread goes to top for them all except the long versions.
     
  9. Milleniumaire

    Milleniumaire

    Joined:
    7 Jan 2010
    Messages:
    616
    Thanks Received:
    6
    Location:
    Yorkshire
    Country:
    United Kingdom
    Thanks SFK. Do you mean the Goldscrew Plus PZ? Do you know how they perform for fixing thin (9mm) ply to chipboard? I'm concerned that without a dowel or a pilot hole in the ply, the ply may not be pulled tight onto the chipboard and I need this to happen.
     
  10. SFK

    SFK

    Joined:
    23 Jul 2010
    Messages:
    2,030
    Thanks Received:
    474
    Location:
    Oxfordshire
    Country:
    United Kingdom
    Yes.

    It will fix them together well.
    But not too sure about its 'pull together' ability as it has a thread along its entire length.

    In those situations I tend to stand where I am screwing in the screw to push the objects together, screw in once to make a pilot hole - but as this can push two surfaces apart I then screw it out and then back in again.
    Sfk
     
    Last edited: 3 Nov 2020
  11. Milleniumaire

    Milleniumaire

    Joined:
    7 Jan 2010
    Messages:
    616
    Thanks Received:
    6
    Location:
    Yorkshire
    Country:
    United Kingdom
    In the end I purchased some Turbogold PZ double countersunk 4 x 25mm screws from screwfix as the Screw Tite 2 screws weren't immediately available.

    As expected for short 25mm screws, the thread went upto the head, however, the ply was still pulled tight to the chipboard, so they did the job. I went through nearly 600 screws without a single head snapping off, so they are good quality screws, fixed using an impact driver.

    Used SFK's advice and stood over each screw, with my feet on either side, in an attempt to force down the plywood.
     
  12. DIYnot Local

    DIYnot Local

    Joined:
    3 Sep 2019
    Country:
    United Kingdom

    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

    Select the supplier or trade you require, enter your location to begin your search.


    Are you a trade or supplier? You can create your listing free at DIYnot Local

     
Loading...

Share This Page