PSE Floorboard Thickness for 200mm joist centres

Discussion in 'Carpenters' Talk' started by Pedal Powered Plumbing, Dec 18, 2017.

  1. I want to replace the battered old chipboard flooring on the 1st floor of my house, as it's structurally unsound.


    The joists are spaced at 600mm centres.

    I will want to access the pipes and cables under the floor in times to come, and so I don't want to use tongue and groove (T&G) boards, as they're a swine to get up again once they're down!

    I plan to use planed square edge (PSE) softwood boards, old school stylee. I will fix them to the joists using screws to avoid any creaking.

    In the process of trying to figure out how thick the boards need to be, I found a document (see link at end of post), which seems to indicate that the boards need to be a minimum of 19mm thick. However, I have a feeling that they're assuming that those boards would be T&G. I understand that floors constructed from PSE are weaker than those constructed from T&G, as PSE boards do not interlock.


    I consulted a timber merchant by email, who responded with the following:

    "Would be surprised if natural redwood flooring was passed at 600mm centres, am no structural engineer or architect but it seems like a lot of air to cover in boards. The norm is 300 or 450mm centres.

    Have stood on a piece of 20 x 145 at 600mm centres and it certainly deflected, this was a piece of clear material without any knots.

    For advice would suggest using a specialist structural engineer or architect."



    Does anyone in the trade have any advice? You needn't be a "structural engineer or architect"!


    Many thanks, Benedict


    https://www.lancaster.gov.uk/assets...ors-Timber-sizes-and-construction-details.pdf
     
  2. KIAB

    KIAB Super Member

    Did a floor some years ago with a 600mm centres, used reclaimed thick flooring from a covent,& plained down to 27mm thickness.

    You can buy 28mm T&G timber, also seen floor done with 25mm ply ripped into strips, looked superb when stained.

     
    Last edited: Dec 18, 2017
    GoodwithWood likes this.
  3. Jord86

    Jord86 Screwfix Select


    22mm chipboard is in regular use along with 600centres, as you don't want t+g, I would recommend KIAB's solution of using inch ply(full sheets though) and fix noggins at the joints to stop any flex.
     
    GoodwithWood likes this.
  4. KIAB

    KIAB Super Member

    Did consider suggesting full ply sheets, but OP wants access under floor to cable & pipes,hence my idea to rip sheets into planks, very common other side of the pond.

    You can 28mm x 137mm whitewood (pine) TP stock it, but only available in Scottish branches.:confused:
     
    GoodwithWood likes this.
  5. GoodwithWood

    GoodwithWood Active Member

    You’ll need to go to at least 25mm for a 600 span. What Is your finished floor surface going to be?
     
  6. This is absolutely great, thank you everybody. Very kind.

    I was planning on leaving the boards as the finished floor surface.

    I had thought about laying it to ply, either ripped, or just as it comes. This is definitely an option. If I did lay it as full boards, I reckon I could probably get away with 18mm, as it's currently laid to 18mm chipboard, and in the areas where it's not damaged, it appears to be performing well.

    My only doubt about ply is with regard to its long term durability. When I take sections up in future, I have my doubts as to whether it'll go back down without the top ;ayer chipping off at the edges. Also, it can't be sanded down when it gets tatty. Solid wood would be preferable.

    What do you all think about using new scaffold boards? Like ply, they're a cost effective option. They would of course require sanding. https://www.theenglishwoodworker.com/workshop-floor-scaffold-boards/

    Nice one, Benedict
     
  7. KIAB

    KIAB Super Member

    Last edited: Dec 22, 2017
    AlvyChippy likes this.
  8. Thanks KIAB. And what a great price!

    Is it necessary to run them through a thicknesser, or can I just lay them as they come? The doors in the area I'm working on are already cut to accommodate carpet, so thick floorboards would close the gap!
     
  9. KIAB

    KIAB Super Member

    You need one face planed,will take stain,finish better, otherwise they are very rough, risk of splinters if you were to walk on them in your bare feet.

    Here a table made from the.

    http://www.rosesandrolltops.co.uk/2017/06/makeover-dining-table-made-from.html
     
  10. AlvyChippy

    AlvyChippy Active Member

    be warned, not having T&G they might creek"... can mess about in that repsect in having them installed on a glued basis or on a small apertures (3000-400mm joist gaps) + fizz glue between them and clamping.
     
  11. AlvyChippy

    AlvyChippy Active Member


    Yes and no, my opinion.
    using scaffold boards is bit peculiar finish, although they are strong structurally, they are fairly soft timber and can get easily scratched.
    I would recommend, not planing them, but after install do "2 step" sanding-
    one- get rid of edges and loose bits (belt sander jobby), give it dry coat, let it dry;
    and two sand everything with 120 hand 1/3 sander, before giving darker stain and final finish to get nice finish and no splinters
     
    KIAB likes this.
  12. Excellent. I am thinking of just sanding the boards down with a floor sander after I've laid them, similar to how the people in KIAB's video did it. That way, the floor should be nice and level. The fact that I don't have access to a planer is also a factor!

    Alvy, what is this 'dry coat' you speak of? Would it be just as good to sad with both coarse and fine paper, and then treat the wood, or is there a reason to treat between the coarse and fine sandings? I will be hiring the sander, so it'd be convenient to get it all done at once.

    Many thanks, Benedict
     
  13. P.S. Can anyone advise me what percentage area I should add onto my floorboard order to allow for waste? I'm guessing that since the distance between my joists is greater than normal, this will result in slightly higher wastage, as any timber less than 600mm couldn't be used in theory?
     
  14. AlvyChippy

    AlvyChippy Active Member

    Any water based protector - sealant, as "diamond coat" or similar (presumably you going the water based coating route)
    Reason is that when finish sanding grain-soft splinters wouldn't lift up, the stain wouldn't look like "paint"- would retain some wood unevenness characteristics, as scaffold boards (depending on many factors), will look rather bland.
    However, seems you trying to get mirror type of level finish (in video results are of "rustic" appearance-finish), using floor sander (midd-coating) it's not necessary.

    and again, be warned, them boards are treated already and are significantly softer than Oak, Ash, or any other hardwood. Minor movement, shrinking will be there and even you will achieve mirror finish initially, it'll scratch. Just like people putting down "real antique pine flooring", but end up with too much of "real wood floor effect" as splits, splinters etc :D

    I'd recommend staining and wax based coating (quick and simple), so the next time in a year or so, you could reapply again without major heartache.

    Waste, depending on a width of flooring used, I allow 20% on anything under 20m2 and 15% over, but non T&G (scaffold board) you most likely to waste even less.
     
    Last edited: Dec 30, 2017
  15. Thanks for your advice Alvy,

    Luckily, I'm not looking for a mirror finish. I mostly want something to walk on to be honest! If it gets knocked about a bit, I'll cope.

    I like the idea of using a water based protector - sealant in the way you describe. Do you have a product in mind? I tried searching for "Diamond coat" as you mentioned it, but didn't find anything.
     
  16. AlvyChippy

    AlvyChippy Active Member

    https://www.google.co.uk/search?q=c...hrome..69i57.341j0j7&sourceid=chrome&ie=UTF-8

    matt will give you little bit better, more durable finish... in min of 2 coats
    just use paint roller- super quick, after first coat within couple of hours it's ready for a gentle something like 320 paper (on a rubber block), before next coat

    The way I see it:
    1 you lay the floor tight
    2 one sanding with either 80 or a 100 (presume professional drum-belt floor sander) (you'll have to pay extra for each belt)
    once happy, 3- 120 or 180 paper over it (also, get some 1/3 sheet or at least palm sander for the very edges sander ready(
    4 coat of stain,
    5 coat of diamond
    6 hand rubber block with 320, just to get it ready for next coat (MUST give it a gentle scrub between coats) or 240 with orbital
    7 final coat of diamond with foam roller.

    8 Post pictures back here with results :D
     

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