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Posted: Mon Sep 04, 2006 1:02 pm
by Steve.W.
I am about to start replacing my existing patio with a natural sandstone or travertine and I'd like some help to know how much extra work I need to do for the bedding layer.
Existing patio (40msq) = Clay base + 40mm sharp sand (no cement) + slabs.
Questions:
1. Is the clay suitable as a sub-base (feels quite solid)?
2. Do I need to remove the existing sharp sand down to the clay base or can I use the existing sand layer?
3. If I use the existing bedding sand should I plate compact down and then ripple before laying the slabs?
4. Do I need to add a 10:1 dry mix to firm up the bedding sand?
5. How do I prevent the ants from digging my new patio up!?
Advice would be very much appreciated 
Posted: Mon Sep 11, 2006 1:42 pm
by Steve.W.
HELP - could someone please reply!
Posted: Mon Sep 11, 2006 8:40 pm
by lutonlagerlout
1. Is the clay suitable as a sub-base (feels quite solid)?
NO
2. Do I need to remove the existing sharp sand down to the clay base or can I use the existing sand layer?
yes it needs to be removed
3. If I use the existing bedding sand should I plate compact down and then ripple before laying the slabs?
its got to be dug out to at leat 200mm below finished flag height
4. Do I need to add a 10:1 dry mix to firm up the bedding sand?.
i think you have been watching groundfarce mate,you need to dig out 200-250mm add 150mm of type 1 ,wack this,then you are ready for a mortar mix and flags
5. How do I prevent the ants from digging my new patio up!but an anteater,alternatively make sure all the cement mix is well mixed so it goes off hard
hope this helps
tony
Posted: Mon Sep 11, 2006 9:11 pm
by rms
You do NOT need 6'' of type one for a patio. 3'' would be ample and in many cases if you use a ground stabilizing membrane, no sub base is required. Just 2'' of ballast and cement or sharp sand and cement (anywhere between 6 and 10 to 1)
Posted: Mon Sep 11, 2006 9:20 pm
by lutonlagerlout
6" wacks down to about 5" which then leaves you 40mm for the bedding and 40mm for the flags
the Op mentioned clay as the soil,would you lay a patio straight onto clay RMS??
cheers tony
Posted: Tue Sep 12, 2006 8:48 am
by Steve.W.
Thanks for all the info. I'm thinking 50mm of 6:1 sharp sand and cement, compacted down and laying the flags on that.
The clay sub base is so hard, is it really going to shift? The current flags have been down 20 years and only just started to move.
Posted: Tue Sep 12, 2006 7:01 pm
by lutonlagerlout
The clay sub base is so hard, is it really going to shift?
ask all the people in london whose houses have subsided,it may be ok for a few years but if it does heave or shrink your patio is NFG
cheers tony
Posted: Thu Sep 14, 2006 6:42 pm
by Steve.W.
Fair point Tony. Thanks.
I may trade off the expense of digging down vs. the fact it's a light use patio and the original clay and patio have been down for a couple of decades with no problems.
Posted: Thu Sep 14, 2006 7:05 pm
by Steve.W.
Sorry,
One other confused question.
Do I lay down the complete coverage of bedding layer and compact in one go (10:1 for individual bedding) or do I do a section at a time. I assume I do in stages as the bedding will harden before I lay all the flags - if it takes me a few days. Thanks.
Posted: Thu Sep 14, 2006 8:09 pm
by lutonlagerlout
the bedding layer doesnt get compacted because it has cement in it and will go hard anyway.
"cavaet emptor" with the lack of sub base mate
cheers LLL
Posted: Fri Sep 15, 2006 4:51 pm
by Steve.W.
Okey dokey,
So... 50mm 10:1 dry, trampled in as I go (no compactor) - understand the risk with laying onto clay sub-base.
Posted: Sat Sep 16, 2006 12:37 am
by lutonlagerlout
thats it mate good luck
LLL
Posted: Tue Sep 19, 2006 9:03 pm
by rms
Worst case scenario, a 40 sq. metre patio is not going to move much even with a clay sub base, if you use a ground stabilizing membrane.