Tarmac vs concrete?

[Crofter]

I'm gradually coming to realise that I will have to put some sort of surface on my driveway. It has worked out a bit steeper than I had hoped and has a sharp bend in it half way down- this is also the steepest part. The total length is about 35m and it is made from rock topped with crusher run that has been graded and compacted as much as a two and a half ton digger can manage (which isn't a lot).

 

The resulting loose surface is, unsurprisingly, a right PITA leading to scrubbing and wheelspinning at the corner.

I've had a quote for tarring the whole lot, at £4k + VAT, and on top of this I would need to budget for some sub base to be rolled onto the existing surface. That's a fair whack.

 

What would be wrong with using concrete instead? I can lay a 100mm slab for a quarter the cost of the tarmac, although I might have to add rebar to that, and buy in timber for shuttering. However it is extremely tempting.

 

The other option to cut the cost is to surface only the steepest part of the drive, at the corner. This would favour concrete again as the on-site cost for the tarmac guys seems to be quite significant. I can get a volumetric concrete delivery so the 3-4 cube that I need would be no problem for them.

 

So... apart from perhaps not looking as nice as tarmac, what's not to like?

[Declan52]

Are you putting kerbs in to stop the sides bursting out???

I am in the same boat. Concrete I can divide the drive up into bays approx 5m*5m and do it myself. It will need cleaned more as when it goes  green it will be more noticeable. 

Tarmac is obviously more expensive and being black hides the dirt better. I have done footpaths before but I think a driveway would be a step too far.

[NSS]

Don't driveways have to be permeable these days?

[Nickfromwales]

12 minutes ago, NSS said:

Don't driveways have to be permeable these days?

I thought that was unnecessary if you have sufficient land drainage / SUDS mitigation measures? 

[NSS]

Our place is essentially at the top of a hill and on free-draining (subsoil is ballast) ground but we still had to put in a huge soakaway for surface drainage from the roof, and our driveway and all pathways have to be permeable. 

[Ferdinand]

If it is on a hill and in the back of beyond, do you need to think about grip?

 

Cross ribbed concrete (ie finished with a plank) might be better for ice and snow, perhaps? That is provided there is a cross-fall on it.

 

If you save on the budget can you put a more interesting and practical finish on the concrete?

 

Ferdinand

 

Edited January 3, 2017 by Ferdinand

[Crofter]

Thanks all.

SUDS shouldn't be an issue, I've n been given any requirements on that (does it even apply in Scotland?) and I have plenty of options for drainage to existing watercourses etc.

 

@Declan52 If I go with tar, kerbs sound like a bit of a headache- presumably these need proper little footings etc, which means digging down into the made up (rocky) ground. Another point in favour of just concreting the whole thing!

 

I will phone the local guy and see if he offers fibre reinforcement- I don't know if you can BYOF* with a volumetric lorry.

 

The main questions are:

- what thickness to lay (I'm guessing 100mm is a minimum, but might a thicker slab let me avoid rebar/mesh?)

- do I need rebar/mesh; if I do use any, how much?

- do I pour the whole c. 12m long slab as one reinforced lump, or split into two or three sections using expansion joints?

 

 

*bring your own fibre

[PeterW]

28 minutes ago, Crofter said:

The main questions are:

- what thickness to lay (I'm guessing 100mm is a minimum, but might a thicker slab let me avoid rebar/mesh?)

- do I need rebar/mesh; if I do use any, how much?

- do I pour the whole c. 12m long slab as one reinforced lump, or split into two or three sections using expansion joints?

 

- 100mm minimum, 150mm is better if the ground below isn't absolutely solid. 

 

- A142 will stop it cracking but is probably not needed in 150mm. If you do reinforce then make your bays the size of the sheets and pour alternate ones. 

 

- Pour as sections - you say it goes round a corner ..?? If so you need to break it around that area as otherwise it will crack and try and move. You can always use drainage slots to do the joints as then you stop water running down it to the bottom when it rains hard. 

[reddal]

We also had a steep drive to surface. Its longer - maybe 150m in total - so cost was very definitely an issue.

 

We got a quote for tarmac - I can't remember the number but it was prohibitive.

 

We ended up getting the steep part (bottom 100m or so) done in concrete - poured in sections with reinforcement as above. Can't remember the spec - but it looks more than 150mm in places? Anyway its been fine for the last few years.

 

The rest (non sloping bit) was done in hardcore with gravel on top. For this section we initially asked for quotes - and got back elaborate plans for preparing the ground, appying different layers etc - it was hugely expensive (the quote was something like £25k iirc!). We ignored all that and arranged it ourselves in a much simpler method for a tiny fraction of the cost. This felt like a big risk at the time since we didn't know what we were doing at the time. However it has been completetly fine!

 

Good luck.

 

- reddal

[ProDave]

Having the bend on the steepest bit is not the best place, think icy weather, car sliding and not going round the bend? Is it possible to re route it first to avoid that and keep the bend on a more level bit? If not, a high kerb seems a good idea to catch a sliding car?

 

I had concrete at my last house, cheap, easy and dependable, but if the ground does sink it will crack and start to look tatty. I have tarmac at the new house and it looks god but boy it is expensive. I don't know why as it was a very quick and easy looking job to just pour it, rake it flat and run a roller over it a few times.

 

One solution if you just want cheap, is just two strips of concrete rather than a wide slab. A local farm here at the top of a hill has this on the steep section (gravel on the rest) and it works very well.
 

[Declan52]

No matter what method you pick you will need to make sure the base is sound. A min of 200mm well wacked in stone or you will end up with ruts as it starts to sink. 

If you are going for tarmacing then you will need kerbs or each time you drive over the edge it will push out and break off. You don't have to use an actual road kerb, not much fun to lift, I am just using concrete garden edge set 70mm high. Cost £2 each last time I bought some. 

For concrete you can shutter the sides so it sets and being stronger at the edge it won't need a kerb.

I would def put it lay it in bays, much easier to get perfect and if it cracks is only a single section to replace. 

[Ferdinand]

Hmmm.

 

Off the wall, but can you use the stuff people here use for reinforcing the driven-on areas of their sites for part of the drive?

 

Are they available secondhand and what do they cost?

F 

[Crofter]

1 hour ago, PeterW said:

 

- 100mm minimum, 150mm is better if the ground below isn't absolutely solid. 

 

- A142 will stop it cracking but is probably not needed in 150mm. If you do reinforce then make your bays the size of the sheets and pour alternate ones. 

 

- Pour as sections - you say it goes round a corner ..?? If so you need to break it around that area as otherwise it will crack and try and move. You can always use drainage slots to do the joints as then you stop water running down it to the bottom when it rains hard. 

Depends what is meant by 'absolutely solid'. The whole thing has been built up using broken rock, so there is certainly no soft material in there whatsoever. I plan to lay a final layer of type 1 and get that rollered.

 

The whole c.12m length that needs done is one continuous curve. I doubt that mesh is going to work at all as I won't be able to work with square slabs, so I am looking at bending rebar to make custom grids for each section.

 

1 hour ago, ProDave said:

Having the bend on the steepest bit is not the best place, think icy weather, car sliding and not going round the bend? Is it possible to re route it first to avoid that and keep the bend on a more level bit? If not, a high kerb seems a good idea to catch a sliding car?

 

I had concrete at my last house, cheap, easy and dependable, but if the ground does sink it will crack and start to look tatty. I have tarmac at the new house and it looks god but boy it is expensive. I don't know why as it was a very quick and easy looking job to just pour it, rake it flat and run a roller over it a few times.

 

One solution if you just want cheap, is just two strips of concrete rather than a wide slab. A local farm here at the top of a hill has this on the steep section (gravel on the rest) and it works very well.
 

 

The driveway is essentially a switchback, as I am dealing with a narrow strip of land and the need to make a significant drop in elevation at the same time. No possibility of rerouting it anywhere, and every lorry of material costs me about £500 so no budget for that anyway.

I've driven up the existing driveway a few times already, a couple of times towing empty trailers, in a front wheel drive hatchback. Took a bit of balls to keep my foot down and plenty of stone was flying all over the place. My FiL made it look much easier in a 4x4! But I don't think there is any need to stop cars from sliding off anywhere, there is a sort of raised bank that would catch you if it went pear-shaped.

I was talking to my Dad (ex roads dept engineer) about this and he thinks the corner will need to done as a full width slab, not two strips. Strips seem to work on straight sections but the possible track of a vehicle going round a corner becomes too wide and its better to surface the whole thing.

 

@reddal thanks for the info on your own driveway, how steep is your drive?

 

@Declan52 yes I would be shuttering the concrete in place, bit of a b*gger on the curve but for a 100-150mm slab not a massive problem.

[Ferdinand]

The approach my father used with out 50mm farm track type drive was to buy a 10 ton load of gravel every decade and accept that in the meantime it would spread and eventually sink into the mud.

 

Very cost effective, but not the way I would do it.

 

Ferdinand

 

[Crofter]

As a general point... am I correct in thinking that the only real downsides of concrete are the need for expansion gaps if the pour is big enough, and the aesthetics?

[reddal]

1 minute ago, Crofter said:

@reddal thanks for the info on your own driveway, how steep is your drive?

 

 

At its steepest something like 1:8? Even a big lorry can get up it - but that wouldn't be the case if it was any steeper I fear.

[joe90]

You can stain concrete. If you dust the surface with a special powder and trowel it in, its permenant ( see some utube vids on printed concrete) This was done around a swimming pool I installed and it looked fantastic, no weeds growing between slabs etc. My wife thinks I am anal but I want " twin tracks" from gate to yard with grass growing in the middle ( its mostly straight) and I will not compromise at all. I have had this in my mind since day one of my dream and some things are about " living the dream".

[PeterW]

2 hours ago, Crofter said:

 

The whole c.12m length that needs done is one continuous curve. I doubt that mesh is going to work at all as I won't be able to work with square slabs, so I am looking at bending rebar to make custom grids for each section.

 

You can make that into wedge shaped sections - run to a central drain point and then make life easier for water run off..?

[Onoff]

At expansion gaps I've always resin fixed rebar into one slab and Denzo taped the other half of the bar where it goes into the adjacent slab. Allows expansion but limits the joint going out of level.