Laying wooden decking - how much movement?

Discussion in 'DIY' started by Tartan_Terrier, May 26, 2013.

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  1. I'm about to lay some wooden decking (pressure treated pine) on my patio. I've been recommended to leave about 6-8mm between the planks to accommodate the movement of the wood due to climatic conditions. How much vertical movement should I expect though?

    The problem is that the height of the decking is limited due to a door which opens onto it. So if I am to avoid digging out the entire 50m2, I've only got about 6mm of space between the top of the planking and the bottom of the door. Is this going to be enough, or should I be spending my Sunday removing 1cm of dirt from my entire patio area?

  2. Don't worry it won't expand that much. Think about old doors... Did they leave a cm under on all sides? As long as you have a couple of mm for thermal expansion you will be fine.
  3. The decking wont expand up by 6mm. Dont forget the 6mm gap between the boards is in practice 3mm per side. A spacer made from a suitable bit of ply makes that bit easier btw. Dont forget to put a 1% slope on the deck to keep it dry, and a good quality membrane/pea gravel layer underneath.
  4. If you're laying it in Oklahoma, about 800 metres of movement is normal this time of year.
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  5. Can I swap my decking for your patio?

    There is decking out our back garden from when we moved in and it's shit. I cleaned it off last year, and put a couple of coats of stain on it. Already in some places the stain has worn off. And it gets slippery in winter when it's soaking wet.

    Give me a concrete slab patio anyday of the week.

    Sent from beyond the grave using the Force.
  6. A2_Matelot

    A2_Matelot LE Book Reviewer

    Concur with Miner - we have a victorian house and as a consequence (around here) they have quite small rear courtyards so when the children were small we decked over ours as the previous tenants has concreted it. It's just a nightmare to maintain, gets wet over winter, traps all organic debris, gets slushy and slimy, needs powerwashing and scrubbing all the time. If you want I'd lay stone down, will last longer and is easier to look after.
  7. Its not that decking is a bad product, but people try to use it as a cheap alternative to masonry in the wrong situations. Wet decking is normally due to it being laid level in a north or south facing location. Any patio laid like that is going to get wet and slimy.

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  8. You should never powerwash decking btw.

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  9. Problems you might encounter in the future with your decking include warping across the grain (due to the grooves),lifting of edges (especially if nails are used instead of screws),very slippy mould growth (especially when wet in the colder months),rats and mice making a home under decking (try to encourage a fox to live underneath instead),future maintenance (I built mine when I was much younger now the annual painting/cleaning is a nightmare).

    Still when completed it should give you lots of pleasure,good luck with your project.
  10. The pressure washer obliterates the treated surface of the timber, leaving an abraded layer of untreated wood for the elements to get into. On the wooden bits of my boat I scrub down once per year with a weak solution of oxalic acid. I do the same to the decking at home and thats all the time it gets. Its lasted 6 years so far.
    I suspect the various potions sold in the big diy sheds are all a variety of snake oil.

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  11. Okey doke, cheers.

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  12. Ideally, the deck surface should not be above the DPC layer (Same applies to patios). Reason being is that when it rains, the splashes will bridge the DPC with a risk of rising damp developing. If you must have it at the height you describe, make sure there is a small gap between the deck and the house wall and build a slight fall in level away from the house to prevent water collecting and bridging the DPC. Avoid damp at all costs as it could become costly to fix.
  13. The distance between the planks is essential for drainage. If you get vertical expansion, take a bit off the bottom of the door.
  14. Ah my friends welcome to the future:

    PVC and Wood Decking :: Plastivan UK

    Composite decking - Doesn't rot, no need to stain just pressure wash it down every 6months to 1 year.