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rotunda problem

I have a 16ft diameter rotunda filled with 5" square slabs 2-1/2" thick. I always find it a pain to remove all the moss algae weeds etc and have decided to point it up. I will of course have to brush out all the moss weeds etc between the slabs before I can do this.' I use a"wolf"purpose made brush for this which does the job well even though it is very time consuming. In order to prepare for the pointing I assume I will need to clear/clean the gaps to hopefuly prevent weeds growing again after it has been pointed. Will laying tarpaulein over the patio to dry it up be beneficial before pointing? Any other suggestions would be appreciated


  • nutcutletnutcutlet Posts: 27,306

    yes to clean out.

    Don't dry things out.

    You're unlikely to get slabs dry enough to suck the moisture out of the cement at this time of year but this could be a problem if you leave it til summer. Wet the slabs, don't dry them.

    In the sticks near Peterborough
  • Thanks for your advice NUTCUTLET but when I remove the weeds etc between the slabs I am left mostly with earth, Do I have to dig this our too? I suppose I thought that having removed the weeds etc by putting on the tarpaulene I would dry up the soil so that the pointing would adhere better Please confirm
  • nutcutletnutcutlet Posts: 27,306

    The more cement you can get between the slabs the better it will last. Very thin cement doesn't survive long. Try and scrape out the dirt to expose as much of the sides of the slabs as you can. The cement needs to adhere to the sides of the slabs not the soil. 

    In the sticks near Peterborough
  • You need to clear at least 1/2" (12mm) depth of soil from the joints or the pointing won't last long.  The more earth you can remove from the joints, the longer the pointing will last.  Blast it out with a pressure washer if you have one.  Use a 3:1 sand to cement mix and keep it fairly dry so that when you take a handful and squeeze it together, it doesn't fall apart.  Too wet a mix will stain the slabs.  Good video here:

    you can make a rounded tool for finishing it off out of an old bit of 15mm copper water pipe if you have any lying around.  Best done when the surface of the slabs are dry to help prevent the mortar from staining them.

    A trowel in the hand is worth a thousand lost under a bush.
  • nutcutletnutcutlet Posts: 27,306

    I'd go with Bob, Gg, My experience is limited to one set of steps. 

    In the sticks near Peterborough
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