New patio: How much water pooling to expect?

Are the slabs actualy on a gradient, or are they 'stepped'?

a few of the last slabs are fractionally above the one before

There may be reason for that, to stop water flowing to the house foundations, but it sounds like the underlaying wasn't quite done/finished properly? But I'm no expert on modern patio laying techniques as I've not been divorced for a while.

Maybe the slabs will settle over time, as the corpse decomposes.

Subsidence caused by something buried beneath?

It's raining again so this has caught my attention once more. I measure a 2mm step between the 2nd and 3rd last slabs:

Subsidence caused by something buried beneath?

I suppose never impossible, but unlikely. That first photo was on Monday. The slabs were laid the prior Thursday before being grouted on the Friday - so 4 days max!

Are the slabs actualy on a gradient, or are they ‘stepped’?

They're on a pretty smooth gradient overall, apart from these minor steps in the wrong direction. And the photo is looking away from the house, so they aren't deliberate to prevent any flow-back.

In my non educated view I would expect it to naturally drain towards the grass. Some pooling IMO will happen, but thats different to getting a swimming pool when it rains.

However from your pics I cant see a swimming pool type scenario happening in the pics?

If you hose the area down does it all stay on the patio?

I would want to lay a straight edge over three rows of slabs across the water from the lawn towards the house. If the slope is even from the first row to the third row other than the pool it would appear the water is pooling where the edge of that slab is a couple of mm low and could be corrected by raising that edge of the slab.

Of course it would have been better if this was  noticed prior to grouting.

here's the problem with large format tiles in 50% brick layout. Particularly prevalent with cheap chinese tile means Warpage or cupping along the longest length means that you can't avoid lippage in the center.  You could split it and have imperfections at the and joints as well as the center of the longest length but the setter has likely just focused on lippage where they butt on the shortest length. 33% overlap is often a solution

Expect it to get worse as the bodies decay...

As Dirk above, I was going to ask are the slabs themselves flat? If they have any kind of bow, then will be physically impossible to have them without small hollows when laid in a staggered pattern.

I've had the same with smaller wall tiles - luckily it looked ok as a "feature", but it explained why the tiles were seconds / cheap.

Looks good to me, it's going to move over time anyway. But we need to address the clinical garden, where are the flowers, shrubs etc. Hope that grass is real.

not just the cheap porcilain, i fit a lot of quite expensive italian/spanish stuff and that can have quite big bows in it, can even be flat for 3/4 of it's length then dive of a mm or 2.
always try and avoid doing 50/50 if possible and sometimes it even states on the box not to.

Just finished laying a porcelain patio last week, all the slabs bowed at the end (900x600mm) although the slabs appeared flat they were anything but , you have to find a happy medium so I level from the highest point.

Obviously I mention this to the customer and show them....but the main objective is to push the water away from the house with the least fall ( bubble off level touching the line)

Expect it to get worse as the bodies decay…

Yeah, that’s what I was implying…