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No they are not a big issue for me for the following reasons
90 - 95% of properties in England are not suitable for permeable paving due to ground conditions
The cost to purchase permeable paving is way above traditional paving costs
you can't purchase small amounts of the 20mm clean stone for the sub base or 6mm clean stone for the laying course as builders merchants don't stock it, you have to order it through Hanson
There is always a solution when faced with changing or extending an existing paving area to dispose of the surface water, we are 21 months into the new planning legislation and I have not come across any situation where I could not install traditional paving whist still containing the surface water within the boundary of the property
We maintain a site that has it's car park laid on permable paving (not sure of make) with slots backfilled with crushed angular grit. It has been down less than 18 months. The car park has a slight slope down to the kerb and this area regularly floods up and over the kerb and covers the footpath due to the drainage slots built into the pavers becomming blocked.
We now have a regular task to clear these slots out by manual means and have considered light jet washing.
The Developers state this is typical of this style of paving.
Appreciate your further (general) views / experience and your recommendation on how Marshalls would approach the issue of blockage ?
Chris Frankland said:
I did the Marshall's permeable training course last year and i must says its a very good course and explains everything in great detail but installing permeable block paving means you have to throw away the manual with the way you have worked installing traditional block paving as the installation is totally different, don't get me wrong its not rocket science either :)
before any work commences on installing permeable paving you need to do a soil test to make sure the ground conditions are suitable, this is not required for traditional block paving
there is additional spoil to remove from site as you need to excavate 320mm depth for permeable paving compared to 250mm depth for traditional paving, bit more cost involved in removing the spoil from site but digging deeper you have got more chance of exposing drains, gas or electric on older type of properties which you then need to cover with ducting or encase in concrete
you can't purchase small quantities of 20mm clean stone from a builders merchants in bulk bags, MOT type 1 is available from most builders merchants, if you order less than a full load either 10 or 20 ton wagon there is a part load charge for the tons the wagon is not carrying and the distance where your working from the quarry or depot can also add additional transportation costs
you can't purchase small quantities of 6mm clean stone from a builders merchants in bulk bags, M grade sand is available from most builders merchants (can't call it zone 2 grit sand anymore) same would apply as the 20mm stone but you would only require a small amount of 6mm clean stone therefore the part load charge will be higher
you need to bed permeable block paving edgings on a full height concrete bed to contain the 20mm clean stone sub base and laying course within the driveway area so it can't spread so this means additional cost of concrete if you use keykerbs both large and small or drivesett kerbs. The only time the concrete bed would be the same as traditional block paving is if your installing the tegula kerbs or a concrete edging as most of this type of kerbs or edge restraint is below ground level
I don't want to mention actual prices as we will all pay different amount per m2 depending on the volume of paving we buy but from enquiries I have made just to buy brindle permeable paving is more than double the cost of traditional brindle block paving
the only faster way i can see is a few hours (if that) in spending time compacting the traditional installation of MOT type 1 sub base and the sand laying course,
instead of making sure the MOT type 1 sub base is compacted as tight as you can get it so the new driveway will not sink, you only compact the clean 20mm stone 2 - 3 times just to firm it up as the voids within the clean stone are for storing the rainwater till it soaks away into the ground and the more you compact it the less voids you will end up with
instead of using a sand laying course to bed the traditional block paving you use 6mm clean stone which is also compacted 2 - 3 times just to firm it up, this will screed a little bit faster than the sand laying course so there is a small saving on time
(it will only be faster screeding if your quick at screeding in the first place, if screeding is something your not used to then there will be no time saving what so ever)
the laying and the cutting of both types of paving blocks is the same
a permeable block paving driveway needs to be maintained 2 -3 times a year so detritus or leaves don't start to clog up and moss or weeds don't start to grow, you can't wash your car on a permeable driveway as the dirt and grime you wash off your car will over time start to block up the clean stone laying course and sub base therefore making the permeable paving less efficient
Anyway getting back on track, It can't be the same cost to install permeable paving as it is traditional block paving when I am being quoted double to buy the blocks, additional cost to dispose of the spill through digging deeper, additional cost for clean stone and additional concrete, but there is a saving of drainage channels, aqua cells and underground drainage.
As for speed of laying, this will depend on the shape and size of the area being block paved, on a good day we will lay 60 - 80m2 sometimes over 100m2 if its a large area or could be less than 10m2 if its a path down the side of the house and is bad access with nowhere to swing a cat round, this would be the same for both types of paving blocks
*NOTE*
don't get me wrong with my comments above, i am not posting this to have a pop at permeable block paving nor is it aimed at Marshall's who's products I have used all my working life and have utmost respect for the staff who i speak to on a regular basis, I am just saying it the way it is out there and please let me know if I am wrong or have missed something because I thought i had every angle covered
I recall on the news a few days before the start of the new driveway legislation back in September 2008 and the newsreader said it was only going to add 5% to the cost of having your driveway paved
I don't know who came up with that figure but over the last 3 years the cost of anything cement based including block paving, the stone and sand tax and the landfill tax on skips tipping etc had risen in price by 8 - 12% per year,
We're getting a lot of very good feedback from experienced paving contractors but I would like to know what is being done to educate the public in respect of permeable paving?
I too attended a Suds, Permeable course in Somerset, October 2008.
Whilst I raise my glass to any manufacturer of permeable products for trying to over come the 95% urban and 5% rural surface water problems we face today.
Having listened intently to the instructor and physically prepared the washed gravels and learnt the exact way to lay the Priora blocks, of which can only be installed one way only, in a nut shell as I understand the whole permeable system is the area below the finished block level is one large or small water tank (dependant on the size of the project), which requires 2 passes of the wacker on the 20mm and zero passes on the 6mm,
My questions, of which were plentiful as the whole concept goes against the grain of procedures for installing a driveway, I needed to know about the water that's flows through the spacings into the holding tank below on the gradient of a drive, especially where the bottom of the driveway meets either the footpath or the road, it wouldn't take very long before the base of the tilted tank fills up and starts to try to back up on its self and it wouldn't take long before the tank starts to spill up and out on to council property.
The solution to this which is an additional cost, by using a baffle system with flattop edging kerbs spanning the entire width of the driveway, like the edging kerb system the concrete must be installed on sub-grade.
with regard to the trial hole, I was told to dig a trial hole 400x400x400mm for every 50 sqm, now my thoughts veer towards including this to the already high price of a 250sqm permeable drive with 80sqm of this being the drive entrance on a sharp gradient, after all if 4/5 holes need to be dug and filled with water, revisited after 12 hours to check that the belt that lies below is sufficient to allow the water to drain of its natural cause, now I want paying for this, according to my tutors, I issue my quotation then dig my trial holes, er not me, how can any price be issued if you have no clarity of what is below.
Don'T get me wrong, I relish change whole heartedly, what I cant get my head around is the long term issues that I believe will occur with the permeable drives, and for that reason only I turn all permeable drive way prospects away regardless whether they are large, medium or small projects, as I cant have my name revisiting because a 4.2 L Jag has caused subsidence whilst running over the surface to the 20mm stone which has been consolidated twice, I believe that the water will also cause the stone to settle down and move around too,
I asked about recessed pavior trays and the trapped water, not even allowed to drill a couple of holes in the tray base to release the pressure, "Not one drop of water to run onto or into drains or roads from the front of the property", er, what about the baffle at the foot of the drive
Until I know that there will be no long term problems with the subases then I'll not lay any permeable products, If any local company who wishes to quote for the projects I bow away from please say.
Good luck.
its funny you should mention the issue of sinking due to the light or zero compaction as I had typed it but but decided to removed it not wanting to look like I was putting the whole concept of permeable paving down
this is my concern too when putting my name to a driveway
due to the sub base and laying course only being lightly compacted this could over time form a rut where the car is driving on and off but because the water disappears through the joints immediately there are never any puddles that appear, now this is where it fall down for me as I would not want to see 2 car tracks on my driveway let alone installing it for any of my customers,
call me old fashioned or call me what you want but that type of finish is not how I have left any of my driveways for the last 30 years and old habits die hard but when your explaining to what is hopefully going to be your next customer and they have asked the question " will my driveway sink like next doors driveway did" then I know hand on my heart when I say "No it will not" that i can back that up 120% with traditional block paving.......I can't guarantee that with permeable paving..."sigh"
not wanting to detract from the original thread and permeable paving but the biggest issue out there at the moment and I can only speak for the North West UK area where i operate but I have been advised its much wider spread too is the total disregard for the planning legislation by paving contractors especially a lot of the patterned concrete guys who don't bother installing any drainage across the end of the driveway/footpath or divert the surface water into a soak a way
another issue is the variation of comments and advice you get from planning departments in different towns, some say you don't need to install channels if the existing driveway was already paved as in like for like so to speak , I was even advised that if you put in for a driveway planning application it will be turned down anyway, now that is wrong
they are not all singing from the same hymn book and they don't have the staff available to police it anyway, the only time they will visit a property is when they have received a complaint and they have to act on it
I don't know if there are any changes in the pipeline now we have a new government but there is certainly scope for improvement with the legislation as it stands
Our experience shows it does become blocked, and with no other drainage channels etc, the sites flood with no other means of dealing with the existing water.
I've had maintenance teams on hands & knees in the pouring rain and 2-3 inches of standing water trying clear the drainage tabs with screw drivers etc on at least 3 occassions this year.
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