With block paving being so popular for the installation of driveways, it begs the question, can I use paving slabs (also known as flag stones) for my driveway? And the answer is yes! But there are some precautions to make before hand.
I think that the main reason block paving is so popular, besides the point that they are specifically designed to withstand the weight of vehicles for driveways, is because they are a cheaper alternative to laying paving slabs. Even the preparation and laying of paving slabs is more labour intensive. In short, you would dig out the area to be block paved, lay and compact type 1 MOT before laying and compacted sand. You then simply lay the paviours, compact them using a wacker plate and brush in kiln dried sand without the need for cement.
How thick do my paving flagstones need to be for my driveway?
There are 2 types of paving slabs which include concrete and natural, such as Indian Sandstone. To be honest, the majority of work we undertake now for laying paving slabs is much more popular, providing many more colours and designs, although not as strong as concrete flag stones.
Large 50mm concrete slabs are the most ideal for driveways as they are heavy duty and can withstand the weight of vehicles with ease. This being said, it doesn’t completely eliminate the want for natural stone flag stones, although the thicker the better. Ideally you would want a depth of 50mm, although 32mm should suffice providing that the foundation is done properly. Avoid purchasing cheap, thin paving slabs as they can move and crack, especially on the edges.
What foundation or sub base is needed when laying paving flag stones for my driveway?
The sub base is the most important part of laying any driveway, whether that be block paving or paving slabs, since the weight of the vehicle can cause the paving to sink or crack. The reason that it’s even more important to have a strong foundation when laying paving flag stones for your driveway is that if there is any movement at all, then the flagstones themselves will crack as well as the pointing, and before you know it you will have loose and broken slabs everywhere! If it were block paving, there is only kiln dried sand used between blocks, so the worst that can happen is you could have dips in places. Of course, this would still need to be remedied by the company that installed the driveway, so be sure to have a signed guarantee!
I would recommend digging the area 7-10 inches deep, before laying 4-6 inches of type 1 MOT. This will need to be compacted by using a wacker plate. If doing the work yourself, you can hire a wacker plate from £40 per day which is a lot cheaper compared to buying one outright! Since ours broke down, we have been renting them since as this has worked out a lot more cost effective.
Once you have your type 1 MOT compacted, it’s time to start mixing a 3 to 1 mix of sand and cement, which should give you a nice 2-3 inches of solid cement between the type 1 MOT and paving slabs once set. Avoid using a dry mix as it won’t set to the strength needed to hold the weight of a car, but be careful not to have it too wet either (as you would when laying a shed foundation) as it would be near impossible to lay the paving slabs without staining them! I would recommend a mortar mix similar to brick laying for best results.
How to avoid loose slabs when laying your paving flag stones
First of all, you want to avoid any air pockets when tampering your paving slabs onto the cement. Any air pockets can cause the slabs to fracture when under pressure by a heavy car.
I would say that the next most important thing to get right is the pointing. Don’t use any ‘quick pave’ style product as this won’t be strong enough to hold the paving slabs together, so providing that you are using a 3 to 1 mix for your foundation when laying the paving flag stones then I would recommend using this same mix for the pointing, as you lay the slabs. Be sure to really shove the cement in between the slabs, making sure that it is will compacted under all of the edges, corners and right up to where the slabs meet. In theory, if you do this as you go along, then all of the cement will set together, from the foundation to the pointing, making it even stronger when holding everything together.
How long should I wait before parking my car on my paving flagstone driveway?
This is really up to you to decide, but when installing these driveways I always ask the customer to wait 3 weeks to be safe. I also put this down on my guarantee document as I don’t want to come back to repair problems because the customer drove on their new driveway way too soon! So far (touch wood) I’ve never had any problems!