Brick gate post on Tarmac

[FoxyChris]

We have a long Tarmac drive that meets the cobbled main road by the side of the house. We are going to have sliding 3 ft high gate across the entrance but after digging out the plans for the house it would seem that every water/gas/electricity pipe in the world runs under our drive.

The Tarmac is in good condition and I was considering building 2 x 4 ft gate posts out of bricks. They won't be load bearing as the gate will slide sideways.

My questions are can i make a concrete base directly on top of the Tarmac and then build the brick post up directly from this. I know the Tarmac was well laid on a good compact base so it's very stable and over 10 years of a 2 tonne pickup truck driving over it hasn't caused any damage. The post would literally be a brick and a half wide so will it be stable?

Will I have to cut in to the Tarmac to make my concrete base first or can I just do it on top? I don't want to lay it on top if someone could just push the post over and want it to be secure to the ground without digging anything up and risk hitting a pipe.

 

[mattice]

Cut, dig and put some concrete in otherwise it will fall over. Quite easy to cut tarmac even with hand tools, even neater with an angle grinder.

 

[JohnD]

To prevent your gateposts tilting, and provide an unusually good footing, dig out your two holes for the pads, and also a trench between them where you can pour a concrete sill. Put a little reinforcement between the two pads and along the sill. You can finish it below ground level if you want paving or asphalt. If it will be exposed, tamp it very well and protect it with plastic sheet or similar so you can keep it wet for at least two weeks. This will build up strength and hardness which reduces wear. It will look neat if you use straight shuttering at ground level - the hidden part should fill the trench.