Help! Patio advice needed :)

[gairloch]

Hi folks,

I'm after some advice I you can help.

Situation just now is that I have an existing patio made up of 3x2 concrete slabs. As it is just now, it's about 30 feet in length (the length of the side of the house), and about 5 feet wide. but fairly uneven in places. The exisiting slabs don't look too great, and having obtained, from a friend, some nice 18"x18" slabs, I figured that I'd lift these existing ones and lay the smaller, but nicer looking ones. I should also say this patio is only used lightly, no cars or heavy equipment near it.

I have lifted one of the existing 3x2 slabs, and found sand beneath it, therefore I assume, there is a sand bedding beneath them all. I will have to remove some of this bedding to even out the level at one side, as due to the aforementioned uneveness, the existing slabs are less than 150mm from the dpc in places. But generally its fairly level, so...

Is they any reason that why I shouldn't just lay these smaller slabs directly onto the existing base, with some additional sharp sand to even the level, after I remove the 3x2's? Or do I need to add some kind of dry cement/sand mix bedding? Or do I bed the slabs with mortar/cement?

Also, I plan to extend the patio in depth to around 8 feet, covering what was a 3 ft wide, cultivated flower border. If I pack the soil in the border down well, and use sharp sand to raise the level as required, should I be safe enough to lay the new slabs onto this base?

Assuming above is ok, I have two remaining questions. Firstly, what fall over the 8ft should I aim for to ensure adquate drainage? Secondly, I had aimed to lay the slabs, butted right up to each other, in fact touching in places, I guess. Is this a problem? Should I leave a actual gap betewwn them? And should I use any kind of wet/dry mortar between them, even considering the, intended, very close proximity of the slabs to each other, or is it not required? Or maybe just brush sand between the joints?

A lot of questions, I know, but any advice, on any point, that anyone with experience of this, has to offer, would be greatly appreciated. Thanks in advance to anyone who takes the time to read and reply.

 

[Thermo]

no reason why you cant lay on a screeded sharp sand bed. Make sure its compacted before you lay it. Same goes for the new area you want to lay on. You dont need any cement in the sharp sand. I usually lay patios to a fall of about a 1/4 of a bubble on a 2.5 metre spirit level, rising slightly more as it nears the last few slabs to the house. Leave a gap betewwen the slabs so they dont touch. Most manufacturers advise against this due to any thermal movement once they are down. Depends on the style of slab as to how you point them. if they are a vertical edge then they can be simply brushed with kiln dry sand (block paving sand) it will take a few goes to fill the joints as thye will settle, but it will lock them in place. Alternativly you can use a dry or a damp mix to point them.

good luck and get the preperation right with the bed and it becomes a fairly easy job after that. (and wear gloves as your hands take a pounding from the sharp sand and the slabs as you lay them.

 

[gairloch]

Thanks for your advice Thermo, it's appreciated. I'll do my best to make sure the preparation is up to the job

 

[nstreet]

I would dig a small hole in the sand to see what it has been laid on. Sometimes you may find its on top of the soil, in which case the patio will become uneven again over time. Ideally it needs a sub base under the sand of hoggin or other type 1 material.

We have a small patio area at the back of our property, its 2 inch of sand on the soil. We get grass growing through and its settled up to 50mm in places. Previous occupants took short cuts.

 

[Thermo]

if its only a patio for foot traffic, then provided the subsoil is compacted with a whacker plate and a good bed of compacted sharp sand is used there is no need for a sub-base

 

[gairloch]

Thanks again for your advice so far guys, hugely helpful

One other thing has just occured to me though, that you may be able to clarify or advise on.

If this sand base is open at any point, ie say the final slab leads up to a flower border or to gravel, what stops the sand from leaking out at that point and the slab dipping? Should i use mortar under the final edge of each external slab on the patio to prevent this, or use some kind of edging product, or build a timber edging to hold the sand?

Or am I just concerning myself with unimportant detail?

Thanks for advice, I'm almost ready to get to it!

 

[Thermo]

good question! You need to bed the last slab in a wet mix of cement mortar to seal the edge. dont use wood it robs!

 

[nstreet]

I have always used concrete edging strips, bedded in mortar or have built a small raised bed from brick around the edge. As Thermo say's wood is a no no.

A neighbour of ours, once laid a brickweave drive without any form of proper retaining around the perimeter. At least twice a year he can been seen lifting bricks and topping up the sand.

 

[Thermo]

oi who you calling masona?????

 

[nstreet]

thats what happens when youre look at two threads at once and downloading via limewire.

 

[pitbull]

I'd put some weed-guard fabric down as well

 

[Thermo]

wont need it if its laid and pointed properly

 

[gairloch]

Thanks guys, all advice appreciated

 

[sandwell]

I have relaid my garden path this week. It was originally laid by my late father-in-law 60 years ago. There was no sand under the slabs, they were laid on coal slack. And it has lasted all these years.

I noticed in Focus today that they are now selling Slab Mix, in bags. It is a mixture in correct proportions of sand and cement by Blue Circle. Would be ideal for your job.

 

[Snash]

Gairloch sorry if I'm butting in on your thread but what you're doing is exactly what I'm planning to do (except I can't afford to replace the concrete 900 x 600 at the moment ).

A couple of questions, what's the best thing to use to compact the soil/sharp sand? Is it necessary to get a whacker? If so can you hire these?

Also, we've got a rodding eye right where we want to extend the slabs - best method of cutting?

Cheers

Snash