Hi guys, Novice here.
I started laying Sandstone slabs on top of my mortar mix (5:1 builder sand to cement). Lots of videos and websites say you can use builder sand and others say sharp sand. Type 1 mot, mortar, and then wet the slab before laying.
All seem fine until I check the next day and around 7-8 of them are wobbling or can easily be picked up. I never put a slurry on them as again some videos I watched, said you don't actually need a slurry mix.
What options do I have now as I never even got to do the pointing and it rained that night I put them down. Do I buy a jackhammer for me to remove the old mortar that's solid?
I've also bought these 2 items for the mortar mix and also for a slurry, but not sure if I'm creating a bigger disaster and if they will help.
As the old mortar is not even a week old, can I add new mortar on top of it?
BOSTIK SBR ADMIXTURE WHITE
BOSTIK CEMPLAS MORTAR PLASTICISER DARK BROWN
Would appreciate any advice and sorry I can't reply as I don't see that option on this site.
Are you a tradesperson and able to answer this question?
Hi There
The only sure-fire fix for wobbly or loose flags is to lift the affected flag(s), break out the bed, put in a new full mortar bed , apply a bond bridge to the underside of the flag to be re-laid, and then put it into place. This method works, every time, no risk of it failing.
Hi,
When the sandstone goes through the cutting process it tends to leave some dust on the underside, which can cause the slabs to not take to the cement as effectively. We tend to brush the backs with a bucket of water and brush/sponge to remove this dust and then you won’t have any problems. The ones that are loose I would break the bed out with a hammer and chisel and replace with fresh mortar, and use a slurry painted on the backs to ensure they don’t come up again.
Don’t panic ! This can be easily remedied.
Take up the loose paving and clean the mortar from the back of the paving, this can be done with a bolster chisel and lump hammer.
Dig out any old mortar and for good measure give the sub base a quick check compact if you’ve disturbed base.
Apply a slurry mix ( cement/sand mix) which will always help with adhesion.
Mix a 5:1 mortar mix using sharp sand/grit sand is preferable.
Make the mix wettish but not sloppy and provide a full mortar bed not spots and bed paving down with rubber mallet.
You’ll be good for pointing up the next day.
In my experience i use primer for any slabs outside, porcelain or Indian sandstone, sharp sand & cement it's great..should not be any dust at all
Answered10 August 2022
0
Anonymous user
Always use sharp sand in your mortar, it is stronger than mortar containing building sand. Prime the slabs with SBR mixed with cement and water, or use Aspects Easy Prime. You will be best pulling the loose slabs up and fully breaking the mortar bed out then relaying them with the SBR bond. Id personally re do the whole thing as its only a matter of time before the other slabs start flicking about.
