The Brew Cabin

What mix\ strength of 'mortar' is recomended for bedding a car drive?

I'm having to lift and re-lay the flags (2" 2x3 and 2x2) on my drive and front path. Not a large area. 35m2 in all. Due to cost restraints I have decided to use the following format:-

Sub base - 100 \150mm DPT1 or 50 mm Crusher
Bedding - 25 \50mm Mortar mix on drive

I had considered concrete base but the cost was prohibitive.

Thanks

Use a relatively weak mortar. A Class V mortar (1:8) is ample.

Under site conditions, we'd use a lime mortar, but this is not always possible for residential projects. Further, using a stiff bed over a flexible sub-base is less than ideal, but it's not critical on a residential driveway. Make the bed 35-50mm thick and you should be fine - you'll find that a semi-dry mix is much easier to work with than a wet mix, and you can use grit sand rather than building sand.

Thanks for the feedback. Probably a silly question, but..... you mentioned that "Further, using a stiff bed over a flexible sub-base is less than ideal, but it's not critical on a residential driveway. "

Is it considered 'acceptable' to use a simple bedding on a subbase for a drive way? Clearly it wouldnt be as strong as mass concrete and mortar but is it a viable option?

I'm really after a simple do it myself fix.
Thanks

The usual rule of thumb is "stiff on stiff: flexi on flexi" and so a flagged driveway (using pcc flags, not wet-cast decorative patio rubbish) would normally be laid using an unbound bed of grit sand.

However, some contractors prefer to use a bound bedding material, and so a weak concrete/mortar is just about acceptable. Using a high-strength concrete or mortar is a waste, so the idea is to provide just enough 'binding' to stiffen the bedding and prevent any minor settlement or erosion, rather than provide a solid base. Larger flags, such as you have, are less popular for vehicle overrun areas nowadays, as we would prefer to use something like the 400x400 or 450x450 Small Element Pavers, which are a sort of half-way between block pavers and big flags, but they are still used, and whether you use clean, unbound grit sand or a weak mortar/concrete as the bedding, as long as they are firmly consolidated when laid, they should be fine. :)

So from your comment do you think a more acceptable formula for the drive would be:-

Sub base - 100 \150mm DPT1 or 50 mm Crusher
Bedding - 25 \50mm Grit sand

These old style paving slabs are PCC, v thick and V heavy, but thats what I have to work with. The previous laying lasted 30 years, and that was on a grit bedding. I'm going to do some test excavations to see exactly the sate of the sub surface.

One more question, 'where to get' the sub base or bedding? Do you recommend going direct to a quarry or use a builders merchants? I may be needing 8 ton of Sub and 2.5 or 3 tons of bedding. I've never had to buy this before.
Thanks again

I'd be happy with your revised spec. There's no need to use a cement-bound bedding for this type of project unless there's a specific reason to do so, such as ground instability or excessive mining by ants.

As I've just replied to one of my email questioners...

"I recommend using a weak-ish sand/cement bedding mix for patio work because it's damn near impossible to get full consolidation of the bedding without breaking the weak wet-cast patio flags, but there's nowt wrong with using unbound, cement-free sand, for proper pcc driveway/highway flags"


As for buying your materials, unless you can buy in full loads (20T or more) the quarries are unlikely to deal with you, so you'll have to go through a BM. :(