The Brew Cabin

Posted: **Fri Aug 26, 2011 6:47 pm**

Hi All,

I hope you can give me a bit of advice, on sub-bases, I have read through the main site, where I have picked up lots, got all my depths and falls from, but I can only see that a sub-base, for a sandstone patio, is sometimes, or "occasionally" required. As a first timer I don't have the experience to know if I need one or not in my situation.

I have dug out the area for my patio, borderstone purestone riven paving, to have a finished height of 150mm below the damp course with a fall of 1:40, with a bedding layer of 50mm 10:1 sand cement.

I have spent the last four days digging by hand in the rain but am now second guessing myself on the sub-base.

It did look better, was quite neat before the rain, there are pegs in their for the levels but you can't see them any more in the mud!!!

Any advice is welcome based on the attached photo.

Also I was going to screed a dry mix, as per the main site advice, but can I mix that in a cement mixer, the main site said to add water to a mixer first which would mean I have to have a wet mortar, or should I mix wet and if so will i need more cement?

The patio will be 6m across and 3.5 deep, with sleeper steps up to the garden.

Thanks alot
Sye

Posted: **Fri Aug 26, 2011 7:06 pm**

Tony McC
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Posted: 01 July 2007,18:54 QUOTE
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Posted: **Fri Aug 26, 2011 7:36 pm**

Thanks Sean, added picture to first post.

Posted: **Fri Aug 26, 2011 7:42 pm**

You only need 3T of type one for 75mm coverage, it is a small price to pay to ensure that your patio isn't going anywhere. Put some terram down first to make sure the type 1 doesn't sink in to the clay or mud.

Your bedding layer is too thick, it should be 20-40mm.

10:1 is strong enough, though most on here would recommend 5 or 6:1. Costs you Â£15 for a few extra bags of cement and makes your patio solid.

Your mix should be semi dry / damp. Mix a little bit at a time in the cement mixer to ensure it is all mixed well. If you put 10 sand, then 1 cement then some water in you will end up with the stuff at the front being too wet and with too much cement in it and the stuff at the back will be dry and have no cement content.
Read here about the mix to use:
http://www.pavingexpert.com/layflag3.htm

Posted: **Fri Aug 26, 2011 8:46 pm**

thanks Carberry,

If I did 75mm type 1 then 25mm bedding I would be 100 below damp course, I suppose I have to live with that or dig another 50mm all over?

The patio is against a single story extension which has quite an overhang, and a gutter, about 35-40cm in all, do you think I could get away with 100mm below dpc, trying to get out of more bloomin diggin!

Thanks

Posted: **Fri Aug 26, 2011 9:00 pm**

You can get away with it if patio is sloping away from house etc but it isn't best practice. 50mm isn't much, it will take you an hour or two to dig that out, it will give you a better patio and it will make you fitter.
Put the time and effort in now and you're patio will last decades instead of years.

Posted: **Fri Aug 26, 2011 9:06 pm**

yes you are right, i will dig it.

Posted: **Sat Aug 27, 2011 6:08 am**

2 things i would add
10:1 is way too weak for anything except bedding drains IMHO
we always use a half bag of cement to 12 shovels of sand for general use,this equates to about 6:1
when a lot of people try to knock up 10:1 they put in a level shovel of cement then 10 great heaped shovels of sand,thereby ending up with 15 or even 20 to 1
second point
i cant lay slabs/flags on 20mm of bedding? does anyone here?
40-60mm is ideal as if you rake it about you can still tap the flag down
you will break a lot of slabs laying them on 20mm
IMHO
LLL :;):

Posted: **Sat Aug 27, 2011 1:15 pm**

Ok thanks I was only going for 10:1 as I read it on here, "patio mix" but thats fine I will will do the half bag and 12 shovels.
I am glad I posted now!

So I will have 75mm type 1 and 50mm (40-60) bedding at 6:1 with a 1:40 fall starting with a finished paving level 150mm below dpc, so I my formation layer will be about 300 deeper than dpc.

Does that sound about right?

Thanks for advice I almost fd it right up!

Posted: **Sat Aug 27, 2011 3:17 pm**

I started digging out the extra 75mm for the sub-base and its all clay, to get to this level was mostly top soil which I am using to level the rest of the garden, will turf over it later, should I keep digging through it? Or live with the paving being 75mm below DPC?

Posted: **Sat Aug 27, 2011 6:29 pm**

Ok, I have decided not to be lazy and find excuses so I am digging deeper, but now need a skip as whats coming out is only good for building bricks with, does anyone know of a skip company in herts that drops of on Sunday?

Posted: **Fri Sep 02, 2011 12:35 pm**

Still working on it, Is groundsure the right terram product for the seperation layer?
Thanks

Posted: **Fri Sep 02, 2011 5:41 pm**

the stuff you need must be non woven fabric
for skips down your way try "holywell" I know the guvnor paddy
LLL

Posted: **Fri Sep 02, 2011 9:10 pm**

Thanks, I could only get the skip on Tuesday in the end, so hopefully get the digging finished tomorrow.

The groundsure must be the stuff, it says non woven.

Found it on the terram website, along with instructions on how to lay a patio; its seems you lot are doing it all wrong

Prepare a loose, medium strength 4:1 cement/sand mix
Starting in one corner, place the first paving slab onto the
course sharp sand and note the area it covers.
Remove the paving slab. Place dab of cement to
correspond with each corner of the paving slab and one in
the middle.
Replace the paving slab over the dabs of cement and level
by tapping lightly with a rubber mallet.

Posted: **Fri Sep 02, 2011 9:42 pm**

crikey!
we have been busted :laugh:
I have used wrekin non woven before ,but the non woven bit is the key to success
cheers LLL

The Brew Cabin

Do i need to put in a sub-base? - Do i need to put in a sub-base?