Patio slope

Discussion in 'Landscaping and Outdoors' started by Twen, May 2, 2018.

  1. Twen

    Twen New Member

    hi all,

    I am a keen diyer and I am building my first patio which is in the garden and not near the house.

    Following various sites online I have dug a rectangle which is 3.6m by 3.15m (11.34 sq m ) which is 182mm deep. This is to allow 100mm sub base, 50mm mortar bed and 32mm for the chosen slabs.

    My question is around the slope to allow run off. I have followed guidance online which recommends 17mm per linear metre (water runs off into flower bed across 3.15m width)

    I have put wooden stakes in, with marks for the hardcore, mortar and slab. I was going to simply put the stakes in to the level needed for the slope and fill with material. However I realised that this means less material ie hardcore etc at this end because the base is reasonably level so not sure if this is right.

    My question is do I need to dig the soil out further than 182mm to create the slope or do I use the hardcore and the already dug out soil level to create the depth needed ?

    Any tips/pointers for getting the foundations/ slope right would be ace.

    Also any recommendations for pointing material would be great.

    Thank you

    Twen
     
  2. candoabitofmoststuff

    candoabitofmoststuff Screwfix Select

    For this type of thing www.pavingexpert.com is the best online source of info by a country mile! I've used the info to do a front drive, a patio and a block paving path. It's all brilliant info.

    On this page;
    http://www.pavingexpert.com/layflag1.htm
    If you go about half way down you'll see that the best thing is to get the slope right at the sub level.

    Good luck with it.
    Regards,
    Cando
     
  3. Twen

    Twen New Member

    Many thanks so it’s the hardcore level I need to worry about that’s great
     
  4. KEVIN NAIRN

    KEVIN NAIRN Member

    Hi Twen, the standard fall on a patio is around 15mm per metre. If the fall is 3.6mtrs then the calculation is: 3.6 x 15mm = 54mm. To achieve this fall, get a dead straight piece of wood or aluminium angle, bang a stake at the start point and a stake at the finish point (you will of course need 2 at the start and 2 at the finish) fix a long spirit level to the straight edge with masking tape, cut a piece of wood 54mm thick as a packer and get your helper to hold the packer on the last stake. Keep banging the stake and rest the straight edge on it until the bubble in the spirit level is level. you now have the correct fall. Before laying the concrete, excavate the soil, TAMP IT DOWN HARD with a hand tamper (100mm x 100mm cast iron on a broomstick) this stops the earth from sinking. You then put hardcore down then concrete to the finished level. I would have 50mm of hardcore and 100mm of concrete, using a heavy wooden beam to tamp it down. You don't need to screed it as any imperfections are taken out by the mortar bed below the slabs. Always use a FULL bed of mortar never 5 blobs, as the slab has no support underneath it and any pressure can crack it. You only screed when laying floor tiles and the screed needs to be flat and level. The excavated ground should be sloped the same as the fall or you will lose 54mm of hardcore or concrete.
     
  5. WillyEckerslike

    WillyEckerslike Screwfix Select

    Personally I think 100mm of concrete is excessive. It's a patio - not a helicopter landing pad.

    Compacted MOT Type 1 (or similar) 100mm deep on top of terram (or similar) and a full bed of mortar should suffice.

    Edit: I completely agree about getting the fall in the excavation though.......
     
    KIAB likes this.
  6. KEVIN NAIRN

    KEVIN NAIRN Member

    Hello Willy, I think you'll find that the recommended thickness for garden paths is 75mm and for patios and drives is 100mm. Any thinner and it may crack.
     
  7. WillyEckerslike

    WillyEckerslike Screwfix Select

    Hello Kevin. The only time I have ever seen concrete used as a sub base under a patio was back in the early 1970's when someone had assumed that 4.5m³ of ready mix would be the same as the 4.5yd³ that had been worked out for the floor that was being poured.... A patio was created out of necessity (and a couple of steps).
     
  8. Ellie Darlene

    Ellie Darlene New Member

    I can feel that you are much concerned about the look of your patio,for this you should consult some specialists , because a well designed patio not only adds beauty to your house but it also increases the market value of your house.
    You can also consult some specialists like https://professionaldriveways.com.au/
    Constructing driveways and patio is a technical field and it should only be done by the specialists.
     
  9. WillyEckerslike

    WillyEckerslike Screwfix Select

    Hi Ellie. This is a UK forum however I assume that spam still tastes as good down under....
     
    The Fox likes this.

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