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Drive Repair - sub base requirements

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Drive Repair - sub base requirements

Postby Wizard9999 » 06 May 2016, 09:22

I need to do some major repair work on my drive. As part of the planning for that I am trying to work out the volume of sub base I will need. So as to avoid hijacking another thread I taken a quote and dropped it here

Mike G wrote:5x2.5 = 12.5sq.m

12.5 x 0.06= 3/4 cubic metre.

From here: http://www.diydoctor.org.uk/tips/tipsconversions.htm there are 1.92 tonnes per cubic metre of Type 1, so:

.75 x 1.92 = 1.44 tonnes. So, on the face of it, two bags (1.6 tonnes notional) should be enough.


Can I just double check that this is the amount required to get a compacted base? In other words I assume 1.92 tonnes would fill more than 1 cubic metre as delivered, but would then lose volume as compacted.

The drive I need to repair averages 2.5m wide and is about 50m long, with a suggested depth of sub base of 100mm after compaction that is a volume requirement of 12.5m3, so that would suggest I need 24 tonnes of sub base. If a standard bag is 0.8 tonnes that would be 30 bags.

Does all of that make sense? Given the amounts involved I don't want to get the decimal place wrong in my calculations!

Terry.
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Re: Drive Repair - sub base requirements

Postby Rod » 06 May 2016, 10:24

1tonne of type 1 covers 5m2 @100mm
So I reckon 2.5T is what you need?

When you say "repair", laying 100mm is more like a reconstruction for a driveway?
What are you proposing to do?
Type 1 is not the cheapest choice.
I wouldn't worry too much about losses due to compaction as final thicknesses are not that critical in a situation like this.
You don't really want to remove too much existing materials unless you have a source for free disposal?

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Re: Drive Repair - sub base requirements

Postby Wizard9999 » 06 May 2016, 11:42

Rod wrote:1tonne of type 1 covers 5m2 @100mm
So I reckon 2.5T is what you need?

When you say "repair", laying 100mm is more like a reconstruction for a driveway?
What are you proposing to do?
Type 1 is not the cheapest choice.
I wouldn't worry too much about losses due to compaction as final thicknesses are not that critical in a situation like this.
You don't really want to remove too much existing materials unless you have a source for free disposal?

Rod


Thanks Rod, yes, repair was a bit of an understatement it is a complete rework I am afraid. I have filled holes for years, but it is clear the drive is nothing more than gravel spread on well compacted earth. If there are cheaper options would be happy to hear about them, but I do want something that will last.

In terms of amounts, if my drive is 50m by 2.5m than is that not 125m2? If so don't I need 125/5 or 25 tonnes? At 1 tonne per 5m2 the 2.5 tonnes you suggest would only cover 12.5m2?

Thanks again,
Terry.
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Re: Drive Repair - sub base requirements

Postby Rod » 06 May 2016, 13:05

Sorry Terry you are correct - I was getting m2 & m3 mixed up.
Good job I'm now retired!

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Re: Drive Repair - sub base requirements

Postby Stargazer » 09 May 2016, 18:23

Try http://www.pavingexpert.com for construction tips and very useful calculators.
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Re: Drive Repair - sub base requirements

Postby 9fingers » 09 May 2016, 19:07

Stargazer wrote:Try http://www.pavingexpert.com for construction tips and very useful calculators.



+1 - A very useful site
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Re: Drive Repair - sub base requirements

Postby Wizard9999 » 09 May 2016, 22:19

Thanks for the link chaps, already found that one but good to know others rate it.

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Re: Drive Repair - sub base requirements

Postby will1983 » 10 May 2016, 11:07

if you are after 20T+ get it delivered by the wagon load instead of in bags. it'll work out a hell of a lot cheaper.
1 wagon load is 20T so if you get one load and see how far it goes you'll be able to better estimate the remiander to be made up in bags.
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Re: Drive Repair - sub base requirements

Postby Wizard9999 » 10 May 2016, 12:53

will1983 wrote:if you are after 20T+ get it delivered by the wagon load instead of in bags. it'll work out a hell of a lot cheaper.
1 wagon load is 20T so if you get one load and see how far it goes you'll be able to better estimate the remiander to be made up in bags.


Thanks. The other thing I am looking into is whether I can get an even better deal if the same wagon that brings the sub base can take away the top of the existing drive that I will be scraping off.

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Re: Drive Repair - sub base requirements

Postby Mike G » 10 May 2016, 13:03

The issue there Terry is loading the lorry. If you have a digger on site it needs to be pretty big to be able to reach into the back of a lorry body (check with your digger driver). Otherwise, you need a truck with a "grab". They don't do a wonderful job of picking up all the scraps, but it's a good compromise if you haven't a digger.
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Re: Drive Repair - sub base requirements

Postby Rod » 10 May 2016, 16:52

You've also got to dump your 20tonnes somewhere to be able to take the waste away or vice versa?
Are you just going to run on sub-base - 100mm is not that thick.

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Re: Drive Repair - sub base requirements

Postby Wizard9999 » 10 May 2016, 21:35

Rod

I'm using this as my main input (others have said the site is good):
http://www.pavingexpert.com/gravel01.htm

An extract says:

Sub-base

This layer provides the strength and competence of the gravel drive. It should consist of a 130mm layer of DTp Type 1 granular sub-base material, hammered down with a vibrating plate compactor or vibrating roller, both available from local hire shops, to an approx compacted thickness of 100mm. For heavier applications, use 180mm of hardcore, compacted to 150mm thick.
1 tonne of DTp 1 covers approx 5 m² at 100mm compacted thickness, and approx. 3.5m² at 150mm compacted thickness.

Surface

This part of the construction is exactly the same as that given above for paths. Any size gravel or other surface dressing can be used for a driveway, although 10mm is the most popular choice. Any aggregate larger than 20mm poses a hazard if flicked up by the tyres of traffic using the driveway.
A harder gravel, such as granite, flint or magnesian limestone is a good choice for driveways. Some of the softer local gravels, such as Cotswold buff limestone or Keuper sandstone, are relatively soft and can be rapidly crushed to dust by repeated trafficking.

It is recommended that the gravel is compacted or rolled to aid settlement, but it may take some time before it becomes thoroughly embedded in the underlying sub-base.


As it is only a domestic driveway with only occasional delivery vans, etc. I had concluded 100mm would be sufficient. Sounds like you question that. What would you think would be required?

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Re: Drive Repair - sub base requirements

Postby Rod » 10 May 2016, 22:46

If you want it to last I would lay a geotextile on top of the existing ground, 150mm subbase topped with 50 of surfacing (20mm gravel).


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Re: Drive Repair - sub base requirements

Postby Wizard9999 » 11 May 2016, 07:13

Rod

Just too check my understanding, when you say 50mm of surfacing, is that the gravel? And when you say 20mm grael is that the size of the grael rather than thickness of layer? Or is the surfacing a layer between sub-base and gravel, if so what? And the 20mm the thickness of the gravel layer?

Thanks for the input,
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Re: Drive Repair - sub base requirements

Postby Rod » 11 May 2016, 09:20

It's 50mm of 20mm gravel
Compare this with the standard footway (pedestrian) construction where you can get occasional vehicular use (drive entrances etc) the spec would be 150 sub base, 50mm base course and 20mm surfacing (BC and surfacing in "blacktop")
If you want a Rolls Royce job with a "Country" look then 150 SB, 50 bitumen BC, expoxy spray covered in a pea shingle of your colour choice.
In the old days, in this part of the world, a hoggin called Romsey Gravel was the best choice (an as-dug material with an excellent mix of stones and clays) which went down hard and looked really good. Very hard to find nowadays sadly.

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Re: Drive Repair - sub base requirements

Postby Mike G » 11 May 2016, 10:53

Rod wrote:If you want it to last I would lay a geotextile on top of the existing ground, 150mm subbase topped with 50 of surfacing (20mm gravel).


Rod


There are a couple of really important things to talk about in this. Firstly, 20mm shingle (still universally known as 3/4" stone) is absolutely the right material: it is large enough to not get caught in car tyres and in the soles of shoes. I never use "pea shingle" (10mm stone) for this reason. Secondly, 50mm is quite deep, and will result in some initial drifting. However, it is probably about right as a starter because the compression from traffic will mean a rake-over it in a few months, and the resulting depth of stone will then be about right. It'll feel too deep at first. Finally, crushed hardcore is a decent sub-base for shingle, and a geotextile membrane is a great idea, not only helping to stabilise the whole thing (believe it or not), but also to reduce the amount of subsequent weeding.
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