The Brew Cabin

Novice first post.
Have read lots on your site and decided to DIY block paving drive (car use). However I struggle with the following:
I have an existing tarmac drive on what is probably a good sub base that has been laid for many years. I intend to remove the tarmac but would like to use the existing sub base. However the depth of the tarmac is far less than what will be the final depth of bedding layer plus blocks. This means that the drive will sit above the level of the footpath. I dont have a problem with a higher drive but....
My question is, what is the best way to create a slope between the drive and the footpath.
I will be using TopPave blocks and therefore a 'multi purpose kerb' with a sloping edge will be available. However I dont think the slope on the kerb will be enough for the transition.
Alternatively should I remove some of the sub base to create a gentle slope near the edge (say for the end metre or so.). Will the reduced depth of sub base affect the load bearing efficiency of the drive. (Afraid I dont yet know the depth of the sub base.)
I dont favour an infil between the two as mentioned in other posts as this will look a botch job.
Is there an alternative.
Your thoughts would be appreciated.
Regards
pete t

i would advise against this as tarmac drives very rarely have class 1 mot under them and if they have it almost certainly wont be 150mm of mot i have seen many diy jobs do what u are going to do all have the same result differential settlement and rutting in around 6 months of the drive going down which will really show up when it rains, i would first take off some tarmac and have a dig down to see what the sub base consists of and how deep it is and then consider your options, but i imagine u will have to have it dug and done right at the end of the day its your house and u want it 100%. if however u go ahaed and use the existing sub base u will probably have to opt for a slopping bullnose kerb edger and have maybe a small bump up onto the drive as i certainly would not entertain removing subbase at the entrance to a drive. good luck.

Suki,
Thanks.
Looks as if I'll be doing a bit of 'digging' this weekend to examine the sub base....
pete t

Have a look what the sub-base is like before finally deciding on a strategy. On some properties, the sub-base can be fine, and, if it's been down a good number of years, you have the added security of knowing that there's no settlement potential. Assuming you;re only going to be using the driveway for cars and, at worst, light vans, then I'd suggest that, as long as you have a good 75mm minimum of sub-base, then it's a better idea to use that than to dig it all out and start again with 100-150mm of new sub-base material that will take years to become as well-consolidated as what you currently have.

For the transition between the driveway and the public footpath, your idea to use a kerb unit to form a short ramp is fine, or you could scrape away at the sub-base to create just enough depth to accommodate the new paving and a minimal bed of 30mm of sand. Personally, I like the idea of using the kerb unbits, and then, if you're still struggling for depth, use an extra-wide border course, perhaps even building in a pattern such as....



...just at the transition will help overcome the level difference.

Tony,
Thanks for that advice. I didnt really want to dig all the sub base up only to put another, deeper one in. Hopefully the existing one will be over 75mm. The transition idea of an extra wide border is good, but I'll have a look at the depth first.
Must admit I feel more confident now.
Thanks
pete t

I have 'dug a hole' in my drive. There are two layers of tarmac. (The drive was re surfaced some 10 years ago). The total depth of the tarmac is about 60mm . The depth of the sub base is about 100mm. By removing the tarmac and using 60mm blocks and about 40mm of bedding sand will mean a raised height of 40mm above current level. If I use a top pave multi purpose kerb this will give a slope reducing the height at the edge by 50% (30mm). ie 10mm above the current level. Therefore If I 'skim' the sub base (10mm) at the edge, the drive and footpath should end up level.
Finally should I have the existing sub base material checked to see if it is suitable. It has obviously settled and compacted over many years but I'm not sure if i can tell the difference between MOT1 and 2 (or any other material).
Pete t

It all sounds fine, Pete. The test to determine just what type of sub-base material you have, and how effective it is, would probably cost more than a new driveway, so don't worry about it. If it's been trafficked for the past 10 years and hasn't rutted or developed "elephant's footprints", it will be fine.

Once you've removed the bitmac, and skimmed-off as required to accommodate the paving at key points, you need to 're-grade' the sub-base, which simply means checking it all for level, skimming off any high spots and filling in any low spots or hollows with DTp1, and then compacting it all again. Although much of it will be firm and solid, the tarmac removal and subsequent tittivating will have loosened the sub-base in places, so it's best to reconsolidate the lot in one operation rather than do bits here and there.

Are you ok with your dpc levels?

Thanks again.
re the DPC. The final level will be below the DPC by more than 100mm.
I plan to use toppave classico blocks which are not exactly rectangular (they have slightly curved sides) and therefore the gaps between the blocks is larger than normal. Toppave recommend using 'classico chippings' brushed in followed by the kiln dried sand. Have you (or anyone else) experienced any problems with these bricks.
pete t

Is "more than 100mm" the same as "almost 150mm"? The Building regs require 150mm between any paved surface and the dpc, and this is the sort of thing that is picked on by a surveyor if you ever come to sell the property.


Anyway, Classico Blocks are fine and the Classico chippings are fine, too, if a little overpriced. For that reason, many installations of Classico disregard the chippings completely and use all sand joints with no apparent loss of pavement performance. :)

Tony,
Thanks again.
The drive only extends about 600mm into the side of the house, at which point there is the front of the garage. The existing height of the drive is 100mm below DPC. The garage is linked to the neighbours house; the drive adjoining that by the same 600mm and 100mm DPC height.
I wasnt aware of the 150mm rule (and presumably the contractor who laid the last tarmac didnt either...). Can I / should I put a short length of say damp proof membrane between the drive adjacent to the houses?
regards
Pete t

How much of the driveway (in linear metres) is in direct contact with the walls of the house/garage? If it's just a couple of metres or less, then don't worry about it, but if it's say, 3m or more, then have a look at a few of the ideas on the Dealing with DPCs page, which are more effective than simply laying a strip of DPC material.

About 600mm in length in contact with the house so I' m not going to worry about it.
I will be starting work next w/e. Only a relatively small job (25 sq metres).
pete t