Concrete questions - Repairing/replacing

[Saddle-up]

I have an old farmyard - thrown up some 30 years ago by an idiot!

Concrete block buildings on 2 inches of concrete laid on top of clay and rubble! Subsidence is a major problem - even the rabbits can dig through these foundations! Some of the buildings have actually collapsed.

I'm now planning to demolish most of these useless buildings and start again. I'll have to get someone in to DO the work (my d.i.y. skills are not THAT extensive :O ) but I'm anxious to get some idea - in advance - of the best way of tackling the job (don't want to be conned by the local cowboy!)

I'm assuming that - after demolishing the buildings - the existing concrete can be broken up and compacted to form a more suitable 'base' for new concrete. I'm also assuming that 4 inches will be enough for MOST of the area - which will have timber stables and pathways for horses - but that the main driveway - which will be used by delivery vehicles and horse boxes - will need ?? 6 inches??

I'm trying to get some ball-park figure on likely cost. I've looked at the very useful price guide on the main site but have NO idea what effect (if any) the existing concrete (breaking up of/compacting of etc.) will have on the calculations (i.e. - is there a saving on sub-base materials, or is this cancelled out by the cost of breaking it up.

The site is on a slope and I've designed the new layout to use the existing levels, so there will be no major infilling etc. Total area is somewhere around 750 square metres.

Any thoughts, advice?

[Tony McC]

Have a read of the long-running Crushers thread in The Craic for more info on the potential benefits.

Basically, cart away is now so expensive that it makes sense to recycle whatever you can. Sub-base material costs around 50 quid per cubic metre, while cart away is about the same, so that's 100 quid per cubic metre to use traditional methods. Alan Goldsack has been using a crusher this week (sorry I couldn't get there, Alan) and might be able to give some info on turnaround costs, but given the area you have, I would definitely be considering bring in a crusher.

As for sub-base depths, 10mm would be a minium, but you might not actually need to go up to 150mm for the trafficked areas, depending on the concrete you plan to use, but we can cross that bridge when we get there.

[Saddle-up]

Thanks Tony. I saw that thread and wondered if it might be part of the answer. I guess I was hoping there was a slightly easier way than lifting all the existing concrete (there's an awful lot of it! As well as all the old concrete block buildings themselves!) I've just been talking to Mr. Bodge-it (local builder who put up my last stable block!) and he reckons his (BIG) JCB will crush all the old concrete/blocks down to useable foundation stuff. Is that feasible? (It's not that I don't TRUST him - it's just that everything is 'I can do that' - and I'm not so sure!

[LandscapeMann]

Is the JCB a crusher or a backhoe? Or does it have a hyudraulic breaker attachment?
LM

[Saddle-up]

Mmm - now you're getting technical. Looking at the pictures on the JCB site, I THINK it's a backhoe Loader. He has a fair range of attachments for it - but would need to ask about the hydraulic breaker.

He did a good (ish) job on the two big jobs he's done for me - a manege and a concrete block lean-to with 3 big stables - BUT this job is much bigger and I'm more than a bit worried that he would be 'over-extending' himself (at my expense!) I think he tends to the 'near enough is good enough' school of thought - which is why I'm trying to find out as much as I can in advance. His response to questions is 'Don't Worry - it'll be fine!' He also grabs all the work he can and runs from one job to the next - and back again - depending on which customer screams the loudest! I guess that's normal but it drives me barmy.

I COULD try and find someone else - but there seems to be a real shortage around here - and at least I KNOW this one (and where he lives!)

[LandscapeMann]

I don't believe a front end loader backhoe will in itself be able to break up your concrete into acceptable sub base material. Tony's Crusher suggestion would be the way to go.

Sounds like you should ask your contactor lots of questions up front. And if his answers are all 'Don't Worry- it'll be fine!"
That is when I would start to worry.
The "grab all the work that he can and run from one job to the next and back depending on who is yelling the loudest". Is not the normal or correct way to do business, in my view.

Buy the mini-digger (they are great fun and very usefull) and rent a crusher.

Too bad you are on the other side of the big pond ( I am in USA)> Sounds like the kind of project that I would love to tackle.

LM

[Tony McC]

JCB is a brand name for excavators, both tracked and on rubbers, 360s and 180s. The bigger machines will crush old concrete, but that's not their primary function and the crushed material is unlikely to be sub-base standard.

The ideal way to work would be to use the JCB to do the demolition and basic break up, and to feed the broken concrete into the crusher for reduction to sub-base type material. It may be that a larger JCB machine would be used for the initial demolition work, and then used to pile up the concrete and brickwork ready to be crushed, before replacing it with a smaller machine, even summat as small as a Bobcat laoding shovel, and use that to load the material into the crusher, and distribute the output, over a number of days.

[Saddle-up]

Mmm - I have a lot of questions to ask Bodge-it (if and when he turns up!) And if the answers are wrong, I guess I'll be looking for someone else.

If we DID do it his way with a 'roughly' crushed base, how critical is this likely to be to the long term stability of the construction. Obviously the road area - which might have the occasional heavy load - would be more at risk, I guess, But for timber stables, might it be 'adequate' with a four inch slab on top? (I guess I'm thinking that MOST of the current concrete block buildings have survived for 30 years, and they're built on rather less than that!)

[Tony McC]

This is one of those 'length of a piece of string' questions. Without seeing what you have, and how well it's crushed, it's not easy to say how it would perform, but if it hasn't been reduced to Type 1 dimensions, then I'd only be happy to use it as a blinding or capping layer.

[Saddle-up]

Thanks Tony, that's helpful. One more quick question for now - what sort of size is type 1? (The stuff I use on my drive and lorry park is 'quarry waste' which is one and a half inch down so I know what THAT looks like!)

[LandscapeMann]

Thanks Tony, that's helpful. One more quick question for now - what sort of size is type 1? (The stuff I use on my drive and lorry park is 'quarry waste' which is one and a half inch down so I know what THAT looks like!)

There is a complete description of Type 1 in the sub grade section of the main website. Good reading and very informative on all aspects of subgrade construction.
LM

[Tony McC]

The grading envelope for a Type 1 material, as mentioned above by LM, can be found here. Basically, it's 40mm to dust.

[Saddle-up]

Cheers guys! I am SO glad I found this site. SOME contractors treat ALL women like blondes!:laugh: Now I'm ARMED and dangerous!

[Tony McC]

There's nowt wrong with blondes! My elder daughter is a blonde ....... this week. :;):