Weatherstruck/ weather struck pointing with lime mortar

Discussion in 'Builders' Talk' started by Rob Denness, May 22, 2020.

  1. stuart44

    stuart44 Screwfix Select

    For that wall I wouldn't use the churn brush. What I normally do for a lime job, is first thing get a 3/1 mix in dry for 5 minutes, then add some water and let it mix for about 15 mins. While it's mixing make sure all the joints are properly raked out. Then let it fatten up for about 15-20. If it's a hot day jet out the joints and then put it on mist and soak the wall. Let the surface dry and mix up for another 5 mins and you are good to go.
     
  2. Rob Denness

    Rob Denness New Member

    Thanks for the advice stuart. I think I was reading some of your posts on another site- noticed your replies were very concise, so thanks for that.

    With regards to sand, what would you use? I have read that some people use a mix of plastering sand, but I'm guessing I wouldn't need any sharp?
     
  3. stuart44

    stuart44 Screwfix Select

    Depends what people call sharp sand. Our local merch calls concreting sand sharp sand. Really, sharp sand refers to the shape of the particles. Sharp sand has angular shaped grains, whereas soft building sand has rounded grains. Coarse sand has larger grains, fine smaller. Well graded has a mixture of different sizes.
    Building sand is easier to work with, so is more popular for pointing.
    When I point stonework with larger joints I would more use a mix of coarse sharp and building sand. When doing brickwork more often building sand.
    If pointing brickwork with really tight joint a really fine sand is needed. If joints are only 2-3 mm, a sand that's been through a 5mm sieve isn't going to work.
    You will find with lime that a sharp sand can still be workable as long as it gets a long mix to get plenty of air into the mix. Don't put too much water in to begin with, as after about 10 mins in the mix it starts to become more workable.
     
  4. Rob Denness

    Rob Denness New Member

    Oh ok. So maybe 2 building, 1 sharp? From my experience with pointing about a 10mm joint the sharp sand in a mix always leaves a fragile crumbly edge?
     
  5. stuart44

    stuart44 Screwfix Select

    Usually best to test out a few mixes before you start. You want one that will be easy to work with, especially with those kind of joints.
     
  6. WillyEckerslike

    WillyEckerslike Screwfix Select

    Another problem with finding the right sand, especially with some of the larger merchant and DIY chains, is that their small bagged products (20kg ish) may not be local to where you're working so might not match the existing (which almost definitely would have been). Sharp, coarse, concreting and plastering sand might all mean the same thing (or not) to different merchants as well - Grr....
     
    stuart44 likes this.
  7. Abrickie

    Abrickie Screwfix Select

    Tbh I’m having trouble seeing you get the sharp neat cut with sharp sand in the mix
     
  8. Rob Denness

    Rob Denness New Member

    Yes, from my experience you only need one grain bigger that say a couple of mm on the cut edge for it the look rough.
    Matching the colour will be a bit of a minefield wherever I get the sand from Imho. Like Stuart44 said: I could probably only experiment with a few trial mixes, but then I suppose any new lime mortar will be fairly 'light' in colour for the first few years? So far the only thing I know for certain is that NHL 3.5 will be a good all round bindero_O
     
  9. Abrickie

    Abrickie Screwfix Select

    If you’re repointing the whole of the wall on the customers property what are you planning on colour matching to ?
     
  10. Rob Denness

    Rob Denness New Member

    In all honesty I don't think it will matter too much. You can see in the photo that most of the joints are knackered and have eroded away a long time ago. As for the customer's property - that's rendered. So really just want something that's not too stark I suppose.
    The customer just wants the wall to look a bit more of a feature by tidying up with the repoint. I'm a believer in function & form
     
  11. stuart44

    stuart44 Screwfix Select

    That's the problem. Go into Bradfords and ask for sharp sand and you get a bag of coarse sand. Go into Limebase and there are loads of different sands graded by their particle size and colour. They all feel sharp, as angular grained sand should really be used with lime to compensate for the higher shrinkage of lime.
    In the old days sand was supposed to be clean with angular particles, but when OPC started to get used for mortar soft building sand was needed to make it more workable.
     
    David Hatim and WillyEckerslike like this.
  12. Rob Denness

    Rob Denness New Member

    Surely plastering sand would be a good happy medium?
     
  13. David Hatim

    David Hatim Active Member

    Are you in Somerset? Or is there a Limebase somewhere else?
     
  14. Rob Denness

    Rob Denness New Member

    I'm in Brighton. I've just rung Conserv and they do a premix mortar, but can't give any advice on weatherstruck
     
  15. Abrickie

    Abrickie Screwfix Select

  16. Rob Denness

    Rob Denness New Member

  17. stuart44

    stuart44 Screwfix Select

    Somerset
     

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