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Best timber for a bridge bed

Discussion in 'In the Garden' started by dornfield, 14 Feb 2021.

  1. dornfield

    dornfield

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    We have a 4m bridge spanning a small river in our garden: nothing fancy, just concrete 'foundations'* built into the banks supporting (small) steel I-Beams across the span of the river, and then a flat timber bed on top of the I-Beams. The timber has deteriorated now to the point that I need to replace the whole deck.

    What would be the best wood to use that is a combination of being naturally resistant to rot, strong and 'attractive' when new and aged state? The 40 timbers that are present at the moment are dimensions 1800mm x 100mm x 50mm. So not huge: expense is not so important as appearance, longevity and strength, as the load bearing needs to be able to accommodate my 90kg bulk perched atop a Countax garden tractor towing a 79 litre spraying bowser! Maybe north of 300kg in total.

    *the foundations have been scoured out by the water over the years, so it's an opportunity to strengthen those whilst the deck is off, but that is another story...

    Thanks for any advice
     
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  3. dornfield

    dornfield

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    As a follow-up: I've just checked whether Accoya would be an option, and although I have heard that it can be quite hard on tools it is the fact that 40 timbers of the dimension mentioned would be close to £4000 that puts me off. Whilst I mentioned that cost was not so important, I think I might have to reconsider that statement!
     
  4. StephenStephen

    StephenStephen

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    cut down oak sleepers would seem like the obvious choice to me...
     
  5. dornfield

    dornfield

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    Oak sleepers would require a lot of processing to the dimensions of the current timbers. Not impossible, but something that would not be simple for me with the available tools that I have, which would not accommodate sleepers. I'd rather buy the timbers direct from a supplier preprocessed to the 1800x100x50 dimensions.
     
  6. bernardgreen

    bernardgreen

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    Elm is very resistant to water, often used for planking the hulls of boats and water wheels in mills.
     
  7. foxhole

    foxhole

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  8. SFK

    SFK

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  9. scbk

    scbk

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    Larch would last a couple of decades, probably cost about £100 for that amount
     
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  11. SFK

    SFK

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  12. HERTS P&D

    HERTS P&D

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    Old railway sleepers fitted into the I beam.

    Anyway, can we have pictures of it.

    Andy
     
  13. scbk

    scbk

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    Don't know about other parts of the country or online, but yes.

    It would only be 20 3.6m lengths
     
  14. Tigercubrider

    Tigercubrider

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    I tend to think railway sleepers
    Buy/rent a chainsaw
    Or use a circular saw to cut slits then chisel them to a sort of tenon
    You don't need to cut the timber down it's entire length, just where it sits in the steel
     
  15. dornfield

    dornfield

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    I'll try to take pictures and post: I am usually flummoxed by this, and the size of the pictures being too big!

    The deck sits in top of the I-Beam, rather than being slotted into them. I have a Stihl chainsaw, but it scares me to death using it for conventional tree work: I'm not sure that I'd want to use it to try to cut sleepers down, and would anticipate that there might be ironwork in old sleepers that could damage the blade, or worse throw the blade upwards: our tree surgeon (for more substantial works) lost a his 'climber' mate to a horrendous 'kickback' accident to the neck a few years ago. He bled out in no time. Gone. I use the chainsaw only when absolutely obliged to do so.

    I'll have a look at the larch option. I'm not too keen on the composite stuff.

    I will attempt to get some images today, or soon.
     
  16. Tigercubrider

    Tigercubrider

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    You'd pay extra, but find a timber supplier that will cut to length.
    I'd allow a gap between each plank.

    I suppose an alternative is to add more metal rails bank to bank, they won't need to be as hefty?
    Then use slimmer decking type planks.
     
  17. Mike13

    Mike13

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    Real railway sleepers are too toxic for direct exposure to water, and the tar that leaks out when you try and cut them clog things up. I had a couple in the garden that were still leaking tar on hot sunny days over 20 years after buying the house, not sure when they were laid, and not sure if they are still allowed to be sold. Most are just freshly treated timber cut to the same size as the originals.
    Alder used to be used a lot for canal lock lining, so must be quite rot resistant.
     
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