Newly Laid Patio Pointing Breaking Down

Twit_Head

Hi All,
Apologies if I am not posting in the correct place but need advice please.
Had a professional builder in to replace fences and build new Indian limestone patio. Work completed couple of days before Christmas 2017. Patio slabs are laid sound, but the pointing (grouting?) is already flaking and breaking up. Only noticed today as not been in garden over winter since work completed less than two months ago.
I am not happy with this as cost a deal of money, but as a female on her own and not in the first flush of youth, I'm afraid builders can side-line me with techy talk
So, question -I am right to be unhappy that the filling (sorry, don't know what was used) is breaking up already? IT was VERY cold weather when the pointing was done - could this affect the finish?
Thank you and would appreciate your thoughts.

bris

Bad time of the year for pointing, yes the weather is probably to blame.


Moisture gets trapped, cold weather, rain etc keeps it from drying out properly, freezes and pops.


Get them back to look at it.

Heedtheadvice

^^^ as per Bris.

Mortar can set under water but rain will wash out cement and then the 'weak'mortar mixture will be saturated. Along comes the frost before the mortar is cured and the water content expands and breaks up the bonds within the mortar and hey presto, it brakes up.
Can also happen if there are forces from adjacent slabs. These forces can be very high from frozen water.

The situation will not be helped if there is movement in the foundations of slabs allowing water (and then freezing) within cracks, even minor ones.

Poor mixing can be detrimental too i.e. if the mix is uneven with small 'lumps' of sand not surrounded by cement. It should really be a homogenous mix other wise there will be strong points and weak points!

That timing given the weather was very bad. There should probably have been two weeks or more of good and certainly not freezing weather for both the foundations and the pointing to cure and gain strength. The builder can add an antifreeze agent during mixture but that is only effective for a little frost not serious freezing and even so the pointing should have been protected against the effects of the weather particularly direct falling rain and insulated against frost.

Anything else is bad practice and the result you describe is not surprising

getmore4less

Resin bonding based products do they have the same issues.

Twit_Head

Thank you for your help. Will be brave and not be bamboozled by builder telling me the flaking. lumps of cement are a 'feature!'

marlot

Resin bonding is more expensive, but works much better.

Justagardener

It sounds as if the landscaper has used the brush in method of pointing.This is where he makes a mix of dry sand and cement and then brushes it in between the slabs. This looks great for the the first month but can, if not finished correctly, flake and break up.
Very often, the dry mix gets brushed in and then not pushed or tamped down leaving air gaps underneath the pointing, then of course the pointing has some where to move to...which enables it to break and flake. and as said previously rain gets in and possibly freezes causing expansion and the whole pointing can break up very quickly.
He might try and do this pointing method again as removing all the pointing is a pain for him. unfortunately if he does, you will be calling him back. whatever he does all the "old" pointing should be removed first. if you want the patio to last it should be wet pointed (sand,cement and water mixed and then smoothed in leaving no gaps below).

garrysibbald

The weather probably paid its part but is probably the secondary reason in my opinion. I also agree that a dry mix if used is not a reliable approach to acheiving longevity
The most likely reason for cracked mortar joints on slabs that we come across is due to slabs that are laid using a "dot and dab" method where bedding mortar is only used on the corners . No matter how good the hardcore footing below , the slab will move through settlement when laid and over time due to earth movement and this causes the mortar to crack. The only reliable way to lay slabs, in my opinion, is on bed of wet mortar. This removes any chance of the slabs moving and as a consequence the pointing is less likely to crack due to movement. (and the slabs will stay level too!
Having said all that, even pointing with a wet mortar will deteriorate over time.

Twit_Head

Thanks again to all for your very useful and informative replies.
You just hope by choosing a reliable contractor and not a cowboy the job will be done right.
Again thank you