Help! Concrete and bricks where I want a hole

[brightspark]

often wondered why no one has made a core drill to drill the old posts out that's slightly bigger than the existing post so it just cuts the concrete out and new post fits in it will make a fortune

 

[Kram]

That would be a 150mm core drill. 141mm to be exactly on size for a 100mm post, but that size is not cheap

 

[Pete.]

I could lend you the gear if you care to come and collect it.

 

[SierraV6]

There is a line of bricks cemented in going all the way to house, with solid deep concrete right where the posts should be. I had a breif go with the sds drill and chisel.
As its a slope, we need to recess the concrete gravel board down 200mm by the post, or chop a lot off it. The bricks and concrete seem too massive to pull out as a lump.

We could get an 8" diamond core drill but they are not cheap. The engine auger should have plenty of power to drive it and Id need to make up a forced coolant spindle adaptor.
Could drill lots of 20mm holes to break it up.

Could smash the bottom half of a post to reveal the 4x 6mm rebars and cement those in, or bolt them down.

Any better ideas?

Thanks
Mark

I had a similar situation a couple of years ago when I started sorting our garden out. First, check that there aren’t any services within the concrete - there shouldn’t be at that depth but check anyway. Then, establish how deep the old footing (if that’s what it is) actually is by digging alongside it. I was fortunate and under the course of bricks the concrete strip was only 250-300mm deep. I found the best way to break it up was to excavate right underneath a short section so that it had no ground support and then hit it very hard repeatedly with a sledge hammer (wear eye protection). If you can get a cold chisel started (in between the bricks?) that may work well. Once I’d broken out a small section I used my longest wrecking bar (5ft I think) to get underneath and lever the concrete upwards whilst hitting it with the sledge hammer - if you get get it into tension it will break much more easily assuming it’s not reinforced. I removed the lot in a day, pure brute strength and ignorance! I later found out that what I’d removed were the footings of an old garage; if you think there may have been a tower block in your garden at some point I don’t think my method will work!

 

[Morrisman]

Cut 1/4” off a stick of dynamite, place on concrete, hit with large sledge hammer.

I read that somewhere, Gold Mine, by Wilbur Smith I think.

 

[the snooper]

If all you have is an sds, drill loads of holes then in with a chisel on the sds

 

[Agroshield]

One stupid thought, this wouldnt be protecting the gas and electric conduits?

SDS drill is better than CAT. It can find gas, electric, water, fibre optic, you name it.

If you are lucky, the water will put out the fire started when the electric ignites the gas.

If you are worried about services, dig down adjacent to the concrete in soft ground to post depth and then mine sideways a little until you see what is there.

 

[outofthefire]

Cut 1/4” off a stick of dynamite, place on concrete, hit with large sledge hammer.

I read that somewhere, Gold Mine, by Wilbur Smith I think.

A bloke I used to work with was a caver, they used to expand tight squeezes by drilling holes with a battery drill putting two or three hilti cartridges in the hole. Then he had a metal rod he'd ground to make a firing pin that they brayed with a lump hammer using a wagon spray suppression flap as a blast shield. I thought they were bonkers caving in the first place, but this tipped them over the edge, but it worked really well for breaking up the rock.

 

[slimjim]

That would be a 150mm core drill. 141mm to be exactly on size for a 100mm post, but that size is not cheap

I bought a 6” one a couple of months ago for £25

That was just the bit, I have the kit upto 4” so the other pieces were not needed.

I suggest you drill across the 4” section, using the sds, drill every 10mm then cross drill at an angle, then break out with the chisel.

 

[slimjim]

SDS drill is better than CAT. It can find gas, electric, water, fibre optic, you name it.

If you are lucky, the water will put out the fire started when the electric ignites the gas.

If you are worried about services, dig down adjacent to the concrete in soft ground to post depth and then mine sideways a little until you see what is there.

I was helping my brother erect a fence, and he ruptured the plastic gas pipe with a spade, it was about 6 inches underground, they repaired it for free though.

 

[Nick67GT]

Cut 1/4” off a stick of dynamite, place on concrete, hit with large sledge hammer.

I read that somewhere, Gold Mine, by Wilbur Smith I think.

Darwin Award?

 

[Kram]

I could lend you the gear if you care to come and collect it.

Thanks for the offer, I have no working transport at the moment, and your a good distance away.
Im hoping I can get this done today with the sds and a core drill.

 

[julianf]

It's amazing what you find in the ground when you start digging, I assumed that my back garden was undeveloped, the house is old and I have the original deeds and plan from when it was built on an empty field. Cutting out footing I found, old foundations, a filled in hole full of rubbish and old bottles, an old septic tank and a well. God knows what was here before, nothing shows up on old maps! I'm just glad the well was already filled in!

I dug a trench for a soil pipe here.

Found a hole large enough to park your average sized hatchback in, albeit nose down.

Gave me the fear, I can tell you.



My old man was in building whilst docklands was being redeveloped. One job they drilled the holes for pilings, and poured in the concrete. Poured in more concrete. And more.

Gave up in the end and drilled the hole somwhere else (not sure how that was possible, but it was a while back).

They never did find out what they were filling in!

 

[outofthefire]

They never did find out what they were filling in!

The underground

 

[Pete.]

The underground

Has happened. There are a LOT of disused tunnels under the city and docks.

I was on a major project where they had to go along both sides of a street asking people to check their cellars for 'water ingress'. Didn't mention the 100 cubic metres of concrete that had mysteriously disappeared from a void they were filling

 

[Kram]

I'd smash that off with a Hilti breaker, but if you need to sink a post through it you could diamond drill it I guess.

This was sound advice. I ordered the drills anyway, but wondered where my sledge hammer hae gone, and how effective it would be...

It was very effective. I want a bigger one.

 

[Pete.]

If in doubt, give it a clout.

The bigger the doubt the bigger the hammer

 

[Parm]

If in doubt, give it a clout.

The bigger the doubt the bigger the hammer

But Pete, things ain’t fair.

I bet you play with some seriously big hammers in your trade ?