Patio Slope Or Fall Is It Needed

[gibbsy09]

Hi I'm going to lay a patio I layed 26, 3x2 council slabs last year on the other side of garden, turned out not bad, but buying my slabs for this one probably 2x2 by 35mm, and a concrete slab hard wearing, but not picked them yet, so bit nervous how this will turn out.

I'm laying it on the surface below it will be 360cm x 360cm, it is ok length wise, but a little shy on the width so I'll have to widen it slightly, as the concrete surface is kind of uneven I'll put sand down to level off the concrete appropriately.

So here's the part I'm nervous about I've read you need a fall or slope of 10 mm for ever 1 metre, to 1.5 metres, so I'm going to create a slope or fall on the concrete, and the part I'm widening I will use type 1, for the base and I'll incorporate the slope in that, the part I can't get my head around is does my fall start with my very first slab, meaning higher at top lower bottom, eg touching bubble on spirit level, or bubble just slightly off if that's even possible lol, or do I start with my very first slab totally level, and slope it gradually.

Lastly as you see from the pic will I run the slope from the top to the bottom, or left to right running into the fence as you see the pic face on, hope you understand why I'm a little nervous, just don't want it sloping down too much and look stupid or dangerous, or is a touching bubble on the spirit level barely noticeable, done those slabs last year, but you can tell I'm a total novice, lastly they'll be layed on a full mortar bed, or screed if mortar is wrong term, apologies for making this thread long.

 

[cdbe]

Create your fall with a string line between 2 posts running from top to bottom - you fall the whole thing as one, not individual slabs. Use a laser level if you have one, or a spirit level on a long straight edge to set it up.

Don't understand about leveling up concrete with sand? And unless it's the angle the whole thing looks lower than the surrounding ground so it could end up as a paddling pool.

 

[gibbsy09]

Create your fall with a string line between 2 posts running from top to bottom - you fall the whole thing as one, not individual slabs. Use a laser level if you have one, or a spirit level on a long straight edge to set it up.

Don't understand about leveling up concrete with sand? And unless it's the angle the whole thing looks lower than the surrounding ground so it could end up as a paddling pool.

Hi thanks for reply I don't have a Lazer, this is just my second DIY paving job and I'm not planning on doing any more, I get the fact the whole thing has to slope, but surely when I lay my first slab, it can't be perfectly level meaning higher at top, lower at bottom, I've seen videos of them saying get your first slab correct, and your set to go I'm a novice help me understand.

The idea behind using sand on the concrete, is to use the sand to level the uneven parts, and when it's level, start incorporating my slope eg more sand at top and having it thin out as I go, to create the fall, then place a membrane on top, is that a bad idea will it not work using the sand on top? I just thought why take away the hard ground just to create, hard ground again, I thought I could cut down the cost this way, and I could get away with it, am I going about it the wrong way, Thanks.

 

[cdbe]

You lay the slabs to a line, like laying bricks but on a bigger scale. The line must slope to the correct fall (which depends on the type of slabs, with textured often needing more).

Normally you would create the fall with your subbase but you can't really do that if you want to reuse that fixed slab, but with care, you should be able to get away with creating the fall (and building up any gaps in that old slab) with your bedding mix - sharp sand and cement.
You need to minimise the amount of bedding material but you'll need a minimum bed of 25mm. Get yourself a long straight edge (a 3.6m length of decking if you haven't got one), establish and follow any existing fall on the slab and set it all out so you have the correct fall and a minimum clearance under the straight edge of slab thickness plus 25mm.

Don't use loose sand, it will compress and get washed out. Think about some edgings (slabs set vertically in concrete) to contain it and form a nice border.

 

[gibbsy09]

You lay the slabs to a line, like laying bricks but on a bigger scale. The line must slope to the correct fall (which depends on the type of slabs, with textured often needing more).

Normally you would create the fall with your subbase but you can't really do that if you want to reuse that fixed slab, but with care, you should be able to get away with creating the fall (and building up any gaps in that old slab) with your bedding mix - sharp sand and cement.
You need to minimise the amount of bedding material but you'll need a minimum bed of 25mm. Get yourself a long straight edge (a 3.6m length of decking if you haven't got one), establish and follow any existing fall on the slab and set it all out so you have the correct fall and a minimum clearance under the straight edge of slab thickness plus 25mm.

View attachment 234753

Don't use loose sand, it will compress and get washed out. Think about some edgings (slabs set vertically in concrete) to contain it and form a nice border.

Thanks pity, I didn't think I was getting a reply lol, so I thought about my sand idea and knew it wouldn't work, but I never thought about filling the uneven bits with the mix, but the slab is pretty much history, I had hired a breaker to get rid of some old fence posts, and just lost patience with the concrete, so decided to rip it out lol, half of the concrete is gone now, and I was just going to start from scratch, can't get on for falling off, awe well not too worry every day's a school day lol.