Newly laid patio disappointment

[Evolved]

We have just invested a small fortune into getting our outside space fit for summer which included having a new patio laid.

We chose some lovely 600x600 honed grey sandstone slabs which when they arrived looked superb, the colour was really flat and smooth. The guy we paid to lay them has done lots of fantastic jobs previously and took his time preparing a very solid base with a nice deep bed of MOT and a full bed of mortar to lay them on. He has done a superb job in laying them but we have noticed after a couple of weeks of being down that they're started to darken and go blotchy in areas, which is detracting from the look we wanted.

I've asked the guy that fitted them why and he's not really sure, did a quick search online and not really found any answers, so thought I'd ask here.

Any ideas why they'd do this?

Edited by Evolved on Saturday 21st May 23:16

[Evolved]

No they're not seal YET as they've not been pointed and finished yet due to the rain. They've been laid onto a full bed of mortar not a spot bed. The MOT base is around 6" thick and very firm and then it's got around 4" of mortar.

It's raining (again) but I'll try and get some pics once it's dried out to show what's happened. It almost looks as though they're constantly wet in areas but we did have a period where we had sun on them for a couple of days so I know they're not.

[Evolved]

Kinkell said:

They've been down 4 weeks and not yet pointed. 4" of wet mortar ? This is not a pro job by any industry standards. That said, stone is a natural material and will have its quirks known as character within the trade and will probably be fine.

Nope didn't say 4 weeks and the pointing is governed by the weather. The job itself was only finished on Thursday but 'some of the flags have been down for around 2 weeks and they've discoloured. Can you explain why 4" of wet mortar is a problem? I'd be more concerned over a thin base but obv looking for advise.

[Evolved]

SAB888 said:

We always use a sand bed not mortar. Wonder if the slabs aren't drying and it's damp showing through from below.

A sand bed for slabs? The block pave he's done is on grit sand and looks great but the patio is on a wet mix of mortar which has now dried obv.

[Evolved]

INWB said:

did he use concrete to set them or use sand? how thick are the slabs?

It was a 4/1 mix of grit and cement for the mortar bed. The slabs are 20mm thick.