Tips for repointing gable end (mortar mix)

Discussion in 'Builders' Talk' started by Poe, Feb 8, 2019.

  1. Poe

    Poe Member

    Hi guys,
    I need some tips on repointing my gable end.
    Its a 1950s semi brick construction. We are in an exposed location so want to make sure the mortar can stand up to harsh conditions.
    I'm happy with doing the repointing but its the mortar mix I really want to get right as I have seen and read so many different mixes using different sands sharp/builders, water proofer/no proofer, lime/no lime/some lime.
    So what is the ideal mix in your opinions.
    many thanks,
    Poe.
     
  2. DIY womble

    DIY womble Well-Known Member

    Washed sharpe sand , NHL 3.5 , 3-1 ratio , no additives
     
  3. stuart44

    stuart44 Screwfix Select

    General rule of thumb is to Use a similar mix to the existing, only slightly weaker. Too strong a mix is not so good for the brickwork.
     
  4. Poe

    Poe Member

    I wouldn't have a clue what the original mortar mix would have been or what strength as the house has been repointed many times in different areas with different mixes.

    DIY womble you wouldn't recommend any cement or additives in the mix at all then.

    Is there no benefit to water proofer being added. I just want to be sure to the how exposed the house is to get a long lasting finish.

    Also some of the mortar deep into the joints is quite crumbly, how deep should I rake these areas.

    Cheers,

    Poe.
     
  5. stuart44

    stuart44 Screwfix Select

    A common mix for houses of that period would have been 6 or 5/1/1 sand/lime/cement.
    Rake out about 20mm or so and clean out the joints. Then wet them down before repointing.
     
    KIAB likes this.
  6. DIY womble

    DIY womble Well-Known Member

    If the original had no cement in it it would still be mint condition , like for like will do ,aesthetics may influence your choice ,
     
  7. KIAB

    KIAB Super Member

    Would wait a few months until risk of frost has past, & we have warner weather.

    Another who would go with 6 or 5/1/1 sand/lime/cement.
     
  8. David Hatim

    David Hatim Active Member

     
  9. David Hatim

    David Hatim Active Member

    Hi Poe,
    You have to be very careful with re pointing brickwork, particularly if it's a bit on the old side, the main rule is that the mortar must be softer than the brick/stone, the reason for this is to allow any rain to drain out through the mortar, otherwise the bricks will become saturated during wet weather, and if followed by a hard frost can possibly blow the face of the brick. To be on the safe side do as previous comment, NHL 3.5 (That's hydraulic lime) ratio 2.5 sand to one part lime. You can buy ready mixed mortar from specialist outlets, look online
     
    Joe the Plumber likes this.
  10. Joe the Plumber

    Joe the Plumber Screwfix Select

    Great advice from David. You can buy lime mortar here:

    https://www.lime-mortars.co.uk/

    I've used them and was pleased with the service and the product. Just note that if you order too much, they don't accept returns (guess how I know.)

    If you do use lime mortar, in spite of what anyone tells you, you DO NOT need to add any cement to it. It dries perfectly well on its own (after, and I love this, 91 days for the stuff I bought, in fact!)
     
    David Hatim likes this.
  11. Poe

    Poe Member

    Hi guys,
    Sorry to bump my old thread but but ran in to a problem.
    I've not repointed yet due to weather and work but over three weeks ago I removed and bricked up the bathroom widow on the gable end and used NHL 3.5 at the recommended ratio, I put a loose sheet over it to prevent the effects of the weather and made sure air could circulate well.
    I was very surprised yesterday to find that the mortar was still very soft in fact I could scrape it out using just my finger nail.
    I need to get on with the repointing in the next few days but really don't trust the NHL and can't sheet down the entire side of the house for months hoping the mortar will harden.
    Am I missing something here, should I add some cement to speed up setting or should I just use a sand and cement mix?
    The mortar I removed well very hard to remove to a good depth, so hard that I ended up using a grinder and dimond wheel to rake out.
    Cheers,
    Poe.
     
  12. KIAB

    KIAB Super Member

    Weather needs to warm up,this time of year it dry out slowly.
     
  13. Poe

    Poe Member

    I haven't got time to wait.
    I've had the scaffold here for a year now and haven't been able to get on with the work due to illness. I can't afford to continue paying for the scaffold rent and need to get this done before I have to make further payments.
    Surely if NHL mortar takes so long to dry out it can only be used in summer months, how do people work with the stuff throughout the year?
    Is meant to be dry next week but how long does it need before any rain fall washes it out.
    Poe.
     
  14. KIAB

    KIAB Super Member

    usually around 72 hours to cure, then it will dry out slowly.
     
  15. Poe

    Poe Member

    Thanks Kiab,
    so providing I get a least three day of fine weather after this time the rain should effect it or wash it out?
    Would adding a small amout of cement to the mix help at all (the original mortar was very hard).
    Cheers,
    Poe.
     
  16. DIY womble

    DIY womble Well-Known Member

    It won't wash out , the slower the drying the better
     
  17. Dam0n

    Dam0n Screwfix Select

    I would use a 3-1 sharp sand to 3.5 NHL for most mortar mixes. Any less and the lime doesn't fully fill the voids in-between the sand .

    That's my understanding of it anyway
     
  18. Dam0n

    Dam0n Screwfix Select

    Also, your place is 1950's is it definitely lime pointed?
     
  19. stuart44

    stuart44 Screwfix Select

    The chances are that it's a OPC mortar.
    When using NHL you need to let it mix for 20 minutes, leave it for 20 mins to fatten up, then mix for a few more. The bricks should be well damped down before starting, and the work misted down for the first week.
    I'm starting a lime repointing job on Monday, but it's an old barn, and I would probably be using a cement mortar on a 50's build.
     
  20. Poe

    Poe Member

    Yeah,
    I'm starting to think a cement mortar would be best after getting through the top layer of old pointing the mortar was very hard and took forever to get back to a good depth, plus this would cure much faster.

    I mixed the NHL pretty much as Stuart44 suggested and was suprised how nice the mix was to work with.

    Going to think it over this weekend but I might just settle on a cement mix.

    Cheers

    Poe.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice