First time diyer - issues laying indian sandstone

[kangaroo19]

Hi all,

Great site, which I appear to have stumbled upon too late (well, hopefully not too late).

To cut a long story short, I am in the middle of doing a DIY 10sqm patio using Indian Sandstone, and I'm concerned I have got it wrong.

Basically....

1. I excavated the area leaving about 110mm depth.
2. Filled with about 60mm of MOT type 1 and compacted.
3. Sawn and smooth 20mm thick calibrated sandstone slabs, varying size.

The next step is where I have issues... Rather than creating a mortar bed (due to lack of equipment and skill), we topped the area with sharp sand at about 25-30mm levelling off with a slight slope. We then topped this with a thin layer or Tarmac Slablayer mixed with water (not spotting) to get the levels right. About half the slabs have been laid. A few hours later and you could see moisture spots showing on top. These have reduced over the past few days, and probably moreso today after some more sunshine.

My questions are...

1. Should I continue on doing it this way or will this result in a very dodgy base?
2. If not, can I sprinkle the current sand level with cement, mix this through and level off again (either wet this or keep it dry??) and essentially use this as a mortar bed (saving taking up all the sand again to mix in a bucket)
3. Do I need to wet or seal the underside of the sandstone slabs to make sure they do not absorb moisture from the bedding?

After my research, I realise that the best approach would have been to lay it on a proper mortar bed the first time, but as this would now take a lot longer is there a way to make a good finish without taking up the existing stones?

Thanks!

[seanandruby]

I think you already know the answer. Rip it up, place a proper sub base 75/100 ml, allow 20 to 40 ml bedding. The way you are going about it will result in rockers and uneven bed once it"s settled. Use SBR for greater adhesion.

[kangaroo19]

I think you already know the answer. Rip it up, place a proper sub base 75/100 ml, allow 20 to 40 ml bedding. The way you are going about it will result in rockers and uneven bed once it"s settled. Use SBR for greater adhesion.

You are right... I did know the answer, I was just hoping there was a quicker alternative!

It's going to be ripped up this week, and I will now do it properly.

With regards to the SBR for adhesion - is that to be mixed in to the mortar mix? or applied to the slabs?

[seanandruby]

read me
and here

I recommend you spend a couple of hours reading above, also more of the main index on both flags and slabs pages.

[Tony McC]

....we topped the area with sharp sand at about 25-30mm levelling off with a slight slope. We then topped this with a thin layer or Tarmac Slablayer mixed with water.....

Laying a mortar bed over sand is a recipe for disaster. What is the sand good for?

The answer is, as Edwin Starr would have said if asked, "absolutely nothing".

It's a later of weakness that could be washed out leaving the mortar unsupported or will settle and take the mnortar (and teh paving) with it.

Mortar bedding needs to be laid over a sub-base, not another laying course.

As Sean says, you've a lot of reading to do......