1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

'Read' a warped rafter end? Cut/drill to relieve?

Discussion in 'Wood / Woodwork / Carpentry' started by Safety First, 9 May 2020.

  1. Safety First

    Safety First

    Joined:
    26 Nov 2011
    Messages:
    404
    Thanks Received:
    26
    Location:
    Somerset
    Country:
    United Kingdom
    I have finished a basic lean to shelter. One of the rafters bent as it dried before putting polycarbonate sheets on so I had to remove the fixings and set it off it's original position. I tried to bend (fight) it before bracing it. But it still wants to be twisting.

    The fascia is the only thing holding it.

    Can anyone point me to some drawings or diagrams about tension in wood.

    From an arborist perspective I get simple tension and compression, but this is beyond me. Also don't want to cut it in half! IMG_20200509_210536.jpg IMG_20200509_210529.jpg IMG_20200509_210615.jpg
     
  2. Sponsored Links
  3. sircerebus666

    sircerebus666

    Joined:
    31 Oct 2019
    Messages:
    1,423
    Thanks Received:
    224
    Country:
    United Kingdom
    Erm.. this might be a silly question but why haven't you considered replacing said warped piece of timber?
     
    • Like Like x 1
  4. JobAndKnock

    JobAndKnock

    Joined:
    30 Sep 2011
    Messages:
    5,313
    Thanks Received:
    1,177
    Location:
    Lancashire
    Country:
    United Kingdom
    I think you'll struggle to find drawings about tension per se. When the boles of trees are converted by being sawn "through and through", the cheapest and fastest way to mill construction timbers, you'll get quite a few boards which can be prone to cupping across the width. In construction timbers this normally isn't significant (see below). Where a tree has been grown in a place such that it has to bend one way or twist to reach the light this can cause crowning or winding along the length, particularly when the boards are dried. The worst examples are normally pulled by the timber processor, so you don't see them, but poor storage (e.g. lack of sticking between boards, boards not stored off ground or left in sheeted) can exacerbate problems in new timber

    What the trade normally do is to order over volume by 5% or so. The carpenters then sight down each board as it is lifted off the stack to check for cup, wind and crowning (bowing along the length). Badly affected boards are rejected for use as longer components, but they can still be utilised for shorter pieces, solid strutting or blocking (or in walls, noggins/dwangs) where he much shorter lengths make cupping or warping less of an issue, as well as being ripped down for bearers, etc where being thinner wind and crowning can normally be taken out by nailing or screwing down. Joists and rafters/spars which are bowed or crowned along the length are installed crown side upper most as subsequent loading from sub-flooring, sarking boards or roofing materials will naturally flatten any crowning out. Only in the worst cases will a jack plane ever be taken to framing timbers to sort out discrepancies

    TBH your best bet is probably to replace that piece. In general no amount of drilling and relieving will do much good and worse risks weakening the timber
     
    Last edited: 10 May 2020
    • Thanks Thanks x 1
  5. Safety First

    Safety First

    Joined:
    26 Nov 2011
    Messages:
    404
    Thanks Received:
    26
    Location:
    Somerset
    Country:
    United Kingdom
    Thanks for taking the time. Shame, but makes sense. I hope the panels have the margin to take whatever the joist end has done without bowing or pulling clear of a seal edge. Really don't want to remove it.... In a year's time, it should have gone through its cycle of humidity and movement? Would you say that long to see what it's potential is?
     
  6. JobAndKnock

    JobAndKnock

    Joined:
    30 Sep 2011
    Messages:
    5,313
    Thanks Received:
    1,177
    Location:
    Lancashire
    Country:
    United Kingdom
    It matters little how long you wait. If it is warped now it probably won't ever straighten itself
     
  7. Safety First

    Safety First

    Joined:
    26 Nov 2011
    Messages:
    404
    Thanks Received:
    26
    Location:
    Somerset
    Country:
    United Kingdom
    Granted, yes not straight. But it will oscillate seasonally with highs and lows of ambient humidity? Worst next year not likely to be wildly different from 5 years time. I hope?
     
  8. Sponsored Links
  9. big-all

    big-all

    Joined:
    12 Jul 2004
    Messages:
    18,628
    Thanks Received:
    1,445
    Location:
    Surrey
    Country:
    United Kingdom
    wood can react one way one cycle or another way another cycle and a different way every cycle
    it can also go stable then unstable
    in general inbuilt forces will tend to repeat movements but not guaranteed
    usually once you get timber in a frame it will still try to move but will be restricted by the surrounding structure
    somtime you can take a bent timber over bend it a bit the other way and once settled in a structure will be fine
    this can often require you to wet the timber well say overnight on wet grass to make it relax a bit
     
  10. Safety First

    Safety First

    Joined:
    26 Nov 2011
    Messages:
    404
    Thanks Received:
    26
    Location:
    Somerset
    Country:
    United Kingdom
    It's weird..... looking at it, I can help feeling that with, say, a spade bit, I could drill out a couple of holes somewhere, and it would relax.....or get worse.

    Think I'll mark it and measure it all up with tell marks.. for now.
     
  11. sircerebus666

    sircerebus666

    Joined:
    31 Oct 2019
    Messages:
    1,423
    Thanks Received:
    224
    Country:
    United Kingdom
    Then you would be left with a warped piece of timber on display with big holes in it.

    Why are you so desperate not to replace it?
     
    • Like Like x 1
  12. Safety First

    Safety First

    Joined:
    26 Nov 2011
    Messages:
    404
    Thanks Received:
    26
    Location:
    Somerset
    Country:
    United Kingdom
    The only aspect of 'display' I am concerned with is the outside view. I.e. panels buckling or pulled off their seals.
    'Desperate not to' is a dramatisation of 'do you think I'll have to?'
     
  13. foxhole

    foxhole

    Joined:
    14 Mar 2006
    Messages:
    17,116
    Thanks Received:
    1,957
    Location:
    Kent
    Country:
    United Kingdom
    I'm sure there are worse timbers sitting in hundreds of home around the country without any ill effect.
     
    • Like Like x 1
  14. 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