Laying course material - Is gravel suitable

[anatol]

I have a contractor laying a new patio for me and I am concerned about the methods they are using.

They laid the patio a couple of weeks ago but the following week when we had heavy rain it flooded because the they did not provide drainage and also they didn't get their levels correct.

I made them lift the blocks and start again. They lifted the blocks, removed the sand layer and are now laying the blocks on a 50mm bed of 6mm gravel. I am rather concerned about this as I always thought sand was the correct medium.

They told me this is the modern method used by installers on building sites. At the moment they have laid the gravel, set their levels and coming first thing Monday morning to finish the work. They are also not doing any compacting of this gravel until after the blocks are laid.

I would appreciate anyone being able to give me some help on this quickly as I only have until Monday morning to decide whether I continue to let the contractors continue with this.

[Ross-Paving]

The gravel is a common feature when invisible drainage schemes are specified, where the drainage system is under the gravel and blocks, generally large commercial projects. These projects use special blocks which are designed with drainage in mind - not Driveline 50 or other normal driveway blocks.
But in your case if they haven't installed drains then the gravel will only create the equivelant of a soakaway with greater water storage capacity than when infilled with sand.
It's not the sand that was stopping the water draining away, it is more than likely poor draining sub-base.
For a patio it should be easy enough to set it up with a fall to enable free draining.
Was the area prone to flooding before the work was carried out? If so the situation should have been made clear and drainage considered as part of the patio scope.

[anatol]

To Ross Paving


Thanks for your reply it was helpful.

I did explain to the contractors that My ground was prone to water logging as the land slopes down towards my home from a distance. I originally had drainage in place the length of my house which had coped well for thirty years. They removed it saying they would create levels which would allow the water to drain to a ground hopper but they got there levels wrong which reulted in my patio area flooding very badly. They also built a small dividing wall between thenew patio and the lawn and never took into consideration that this was a barrier for the water coming down the slope with the result tha my lawn became a swamp.

[Tony McC]

Sounds like they've bollocksed up. Laying on gravel is NOT suitable for driveway paving unless it is a SUDS installation. I'm fairly confident yours isn't, and that these clowns have seen a picture of a permeable pavement being constriucted on grit/gravel and assume d that it is the "latest idea", when it's not - it's a completely different technology.

If they can't figure out that a sub-base needs to drain, perhaps they should go back to their day job with the donkeys on Blackpool beach.