Efflorescence, haze or not sealing back of slab?

Patio flagstones (slabs), concrete flags, stone flags including yorkstone and imported flagstones.
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rolysatch
Posts: 39
Joined: Sat Feb 19, 2011 11:42 am
Location: sussex

Post: # 109465Post rolysatch

hi

i'm a diyer but haveing a crack at laying my own patio with the help of the site and helpful advice on here, so thanks for that. i've done the brickwork which went fine and have started laying the slabs.

i used a pointing gun and having never used one before didn't realise how long the very wet mortar would take to start setting ready to rub the joints. i did it in the evening (trying to fit it around work), and it still hadn't gone off enough when it was starting to get dark so i had to rub the joints much earlier than i would have liked. this made a bit more of a mess than i would have liked but managed to clean them up reasonably well the next morning with a sponge.

the slabs are tumbled camel dust, which i laid on a full wet bed with a bit of sbr in the mix and wet the back of the slabs before laying.

it's hard to see from the photos but some of the slabs have a bit of white speckling on them. nothing major but they weren't like that when i laid them. and i was wondering if it's efflorescence, sort of a grout haze from where i sponged off the slabs or if it's because i didn't use a bond bridge with a wet bed?

i've still got a lot to lay so if i can avoid any more of this it would be good. if anyone has any advice or suggestions it would be really appreciated. if you see anything else where i'm going wrong i'm happy to hear any critism of what i've done too. pics below.

thanks in advance

roly



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lutonlagerlout
Site Admin
Posts: 15184
Joined: Fri Aug 04, 2006 12:20 am
Location: bedfordshire

Post: # 109466Post lutonlagerlout

Roly
most blokes on here point the whole lot when the job is done,pointing piecemeal is a huge fail
if you use larssen or easipoint it goes off in around 30 minutes
what mix are you using?
this could be the flags wicking cement into the stone
cheers LLL :)
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rolysatch
Posts: 39
Joined: Sat Feb 19, 2011 11:42 am
Location: sussex

Post: # 109467Post rolysatch

lutonlagerlout wrote:Roly
most blokes on here point the whole lot when the job is done,pointing piecemeal is a huge fail
if you use larssen or easipoint it goes off in around 30 minutes
what mix are you using?
this could be the flags wicking cement into the stone
cheers LLL :)

hi lll
thanks for the reply. regarding the pointing as i'm only getting weekends to lay them and i had read on the site that they should be pointed soon after laying, i figured i had best point them up. i'm only about 1/3 layed so far - i'm having to use buckets to carry the sand 200 yards to the back of the house as lots of steps, and then knock up myself with the mixer, and i'm nowhere near as fast at laying as you guys so it's slow going - so the rest will be layed over the next 2 weekends. shall i wait until the end of the job to point the rest or is 2 weeks too long? what's the issue with piecemeal pointing?

the slabs were layed on full wet bed of 6:1 sharp sand and the pointing is 4:1 building sand/cement. i don't need it to go off faster i just need to start the job earlier lol.

as far as the wicking of cement, so should i use drier bedding mortar and sbr bond bridge?

thanks

roly

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