Posted: Mon Nov 07, 2011 2:17 pm
Hi there,
My question relates to the depth of excavation required.
I am installing a new patio in my garden where there used to be grass. The patio is for light foot use only.
The area is about 20m2 and I am using something similar to the following cast concrete riven paving stone (http://direct.tesco.com/q/R.210-1252.aspx) 600mm x 600mm x 35mm. My intention is to have the patio at the same elevation that the grass was previously.
I have skimmed off the grass and taken it to the dump. These removed pieces were approximately 60mm – 90mm deep (soil depth).
The person helping me told me that I then needed to dig down to the hard sub-soil layer which was another ~250mm down, i.e. removing ALL of the top soil. We proceeded to do this over half of the area and dumped the top soil at the dump. I continued removing the top soil myself the following day and kept the top soil in a pile elsewhere. About ¼ of the patio site is still to be excavated.
I have now seen on this web-site that only 100mm of sub-base is recommended with no mention of digging down to the sub-soil. I have also looked at how much hardcore I would need to fill the 250mm and was shocked at the volume (and price) required! Approx 10 tonnes would be needed.
My question is therefore – should I continue digging down to the sub-soil and build up ~250mm of hardcore, OR, fill in the hole I have already dug with the remaining pile of top soil and compact and spread to an even level, before applying ~100mm of compacted hardcore? Note that cost is a major factor in this project and I only intend to be in this property for approx 5 years.
Really looking forward to some advice.
Thanks,
Euan
My question relates to the depth of excavation required.
I am installing a new patio in my garden where there used to be grass. The patio is for light foot use only.
The area is about 20m2 and I am using something similar to the following cast concrete riven paving stone (http://direct.tesco.com/q/R.210-1252.aspx) 600mm x 600mm x 35mm. My intention is to have the patio at the same elevation that the grass was previously.
I have skimmed off the grass and taken it to the dump. These removed pieces were approximately 60mm – 90mm deep (soil depth).
The person helping me told me that I then needed to dig down to the hard sub-soil layer which was another ~250mm down, i.e. removing ALL of the top soil. We proceeded to do this over half of the area and dumped the top soil at the dump. I continued removing the top soil myself the following day and kept the top soil in a pile elsewhere. About ¼ of the patio site is still to be excavated.
I have now seen on this web-site that only 100mm of sub-base is recommended with no mention of digging down to the sub-soil. I have also looked at how much hardcore I would need to fill the 250mm and was shocked at the volume (and price) required! Approx 10 tonnes would be needed.
My question is therefore – should I continue digging down to the sub-soil and build up ~250mm of hardcore, OR, fill in the hole I have already dug with the remaining pile of top soil and compact and spread to an even level, before applying ~100mm of compacted hardcore? Note that cost is a major factor in this project and I only intend to be in this property for approx 5 years.
Really looking forward to some advice.
Thanks,
Euan