Posted: Wed May 19, 2010 12:05 pm
Please can anybody help me with a problem with my drive and patio, laid at substantial expense (in Altrincham) about 4 weeks ago.
A local contractor laid the patio first of all and then the driveway 2 weeks later (about 80sq/m in total). The flags are Indian sandstone laid on a full bed of concrete (MOT base etc) with cobble edgings.
Within 3 weeks of the patio being laid, we noticed that the pointing was starting to crack badly at the edges of many of the flags (where the flag actually meets the mortar on one or both sides). The flags on the edge of the raised patio then started moving, as the pointing was not holding them in place. After this, the same things started to happen with about 2/3rds of the driveway, but strangely most of the cracks are on the part of the drive we weren't driving on.
The contractor lifted and re-set some of the problem flags and then re-pointed a large area, saying that plasticiser had not been used in the mortar mix (it was clearly badly mixed as there were lumps of sand in the mortar).
However, the new mortar is now cracking again at the edge of some of the flags (I am not sure if I can attach a picture of this?). When there is a thin film of water on the flags, if you step on a corner, bubbles come out of the cracks.
I have told the contractor that I believe the flags are not correctly bedded into the concrete and that, as they are moving when walked on, the mortar is cracking. He does not accept this and says that the flags are "flexing" and that air pockets in the concrete base are leading to the bubbling. He says there is no sign the flags are moving when they are dry and the mortar hasn't bonded because the flags must have been old stock and not as porous as newly cut ones.
The contractor is now saying the whole drive/patio should be sealed with matt Picseal to stop water getting in to the cracks and that the seal will set it all solid. I have my doubts this will work - are we just papering over the cracks?
I have read some other replies on here from Tony saying "you may still get micro cracks within the mortar, but it's not critical unless the cracks are at the interface of the flags and the mortar, which indicates the flags are moving and aren't settled down fully".
I am concerned that come winter, water in the cracks will freeze and the mortar will pop out.
Could anybody "in the know" please comment on this problem and tell me whether the drive and patio needs to be re-laid or whether it sounds like this can be resolved. I would really appreciate any help you can offer.
A local contractor laid the patio first of all and then the driveway 2 weeks later (about 80sq/m in total). The flags are Indian sandstone laid on a full bed of concrete (MOT base etc) with cobble edgings.
Within 3 weeks of the patio being laid, we noticed that the pointing was starting to crack badly at the edges of many of the flags (where the flag actually meets the mortar on one or both sides). The flags on the edge of the raised patio then started moving, as the pointing was not holding them in place. After this, the same things started to happen with about 2/3rds of the driveway, but strangely most of the cracks are on the part of the drive we weren't driving on.
The contractor lifted and re-set some of the problem flags and then re-pointed a large area, saying that plasticiser had not been used in the mortar mix (it was clearly badly mixed as there were lumps of sand in the mortar).
However, the new mortar is now cracking again at the edge of some of the flags (I am not sure if I can attach a picture of this?). When there is a thin film of water on the flags, if you step on a corner, bubbles come out of the cracks.
I have told the contractor that I believe the flags are not correctly bedded into the concrete and that, as they are moving when walked on, the mortar is cracking. He does not accept this and says that the flags are "flexing" and that air pockets in the concrete base are leading to the bubbling. He says there is no sign the flags are moving when they are dry and the mortar hasn't bonded because the flags must have been old stock and not as porous as newly cut ones.
The contractor is now saying the whole drive/patio should be sealed with matt Picseal to stop water getting in to the cracks and that the seal will set it all solid. I have my doubts this will work - are we just papering over the cracks?
I have read some other replies on here from Tony saying "you may still get micro cracks within the mortar, but it's not critical unless the cracks are at the interface of the flags and the mortar, which indicates the flags are moving and aren't settled down fully".
I am concerned that come winter, water in the cracks will freeze and the mortar will pop out.
Could anybody "in the know" please comment on this problem and tell me whether the drive and patio needs to be re-laid or whether it sounds like this can be resolved. I would really appreciate any help you can offer.