Driveway threshold bedded with c7.5

[DIY Tom]

Yesterday, I happily started laying the edge course to my new driveway. I've followed the guidance on the edging page... Or so I thought.

I've been bedding with a semi dry c7.5 and haunching with c20.

I happened to re-read the edging page tonight and noticed that c20 is recommended for edging likely to be trafficked by vehicles. I've already finished the threshold with a c7.5 bed. Have I totally screwed up?

As it happens, I had to repair a fair chunk of the pavement right in front of the threshold. I completely dug away and tidied the area and filled it with the c20 haunch mix (down to the same depth as the bedding). I'd say the haunching is about 15-20cm wide. After cleaning up at the end of the day I also put spare c20 against the bedding on the inside of the threshold.

Picture hopefully attached here: Picture. The blocks shown are 200x134.

Any thoughts or suggestions? Perhaps if I were to bed the first row or two of blocks with c20, that'd give it extra strength?

[dig dug dan]

What's going to be the actual driveway surface?

[DIY Tom]

It'll be block paving. The same blocks as shown in the picture (albeit with different sizes). Woburn rumbled. 200x134, 134x134, and 100x134.

[dig dug dan]

It'll be block paving. The same blocks as shown in the picture (albeit with different sizes). Woburn rumbled. 200x134, 134x134, and 100x134.

In that case, you have haunched too much behind the blocks. I presume the front will have fresh tarmac on, and providing you have bedded the blocks on concrete, on consolidated sub base, it will be fine.
But the haunching will need to go altogether on all the internal sides, or you wint be able to lay any blocks

[DIY Tom]

Thanks for your reply!

I presume the front will have fresh tarmac on, and providing you have bedded the blocks on concrete, on consolidated sub base

Yes, I've got a bag of cold lay that will hopefully do the trick. And yes, semi dry c7.5 concrete on decent base.

But the haunching will need to go altogether on all the internal sides, or you wint be able to lay any blocks

Is that because of how it looks in the picture? I think the angle might be a little misleading for the internal haunching. See this picture for a better angle: Picture

Is it worth bedding the first row or two on c20, or is that just overkill?

Cheers!

[Tony McC]

While it *is* better to lay on a C20, it's not the end of the world if a C7.5 is used in its place. After all, we lay road kerbs onto C7.5 and they tend to cope with vehicles running over them....most of the time.

However, on the internal face of the edge course, you do need to trim that spread concrete so that it's flush with the edge face of the blocks, otherwise it can lead to a problem of differential settlement, where the blocks adjacent to the edge course will not compact/settle quite as much as those of a full sand bed. It should look summat like this.....

[DIY Tom]

Understood. I'll trim and make flush. Thanks guys!