Hi All. I need to lay a concrete base at the top of my garden, it will be laid on soil, it will be 4 sq metres X 15cm thick. I will be putting my new bunded 1000 litre heating oil tank on it. Will a 5 to 1 mix be suitable?, shall I put in an additive?, and should I lay anything on the soil before pouring like plastic sheet, or gravel as some UTUBE vids recommend. Thanks for any help
concrete base
- Thread starter Barkas
- Start date
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I would digout an extra 50mm deep and make a sub-base out of old bricks, broken slabs, rubble etc. Hit them hard into your soil with a club hammer (watch your eyes). couple of bags of building sand spread over rubble to give you a smooth surface. Then lay some thick plastic down over the area as a membrane. Then conrete. 5 ballast to 1 cement should be fine.
If you've got no old bricks and rubble then put it straight on to your soil. It would help if you compacted the area somehow first though.
If you've got no old bricks and rubble then put it straight on to your soil. It would help if you compacted the area somehow first though.
I can't see the need for a membrane when this will be an open concrete slab!
150mm will be more than enough, but just be sure that by digging 150mm down from the surface, that you are not still in the soft vegetation layer.
If you are you may need to go down another 100mm or so and then fill with hardcore. You just need to dig and see what you find
Or just drop some mesh into the slab - this may be helpful to deal with any point loading from your oil tank too
150mm will be more than enough, but just be sure that by digging 150mm down from the surface, that you are not still in the soft vegetation layer.
If you are you may need to go down another 100mm or so and then fill with hardcore. You just need to dig and see what you find
Or just drop some mesh into the slab - this may be helpful to deal with any point loading from your oil tank too
To membrane or not to membrane ? That is the question. Wether it be nobler of the mind to suffer the slings and arrows of outrageous fortunes.
All i said was........i would.
1000 litres of anything is alot of weight. Wet and damp winters have a habit of helping things sink. How wonderful it would be if things 'sunk' evenly. And didn't cause premature cracks. But they don't sink evenly very often. A membrane would/should help the concrete keep a little drier by virtue of the fact that it is not in constant contact with the wet and damp grounds that we encounter during our long and ardous winters. And thereby give every chance of aforementioned concrete to not crack.
It's up to you.
Not a lot of work involved in unfolding/unrolling some plastic is there ?
All i said was........i would.
1000 litres of anything is alot of weight. Wet and damp winters have a habit of helping things sink. How wonderful it would be if things 'sunk' evenly. And didn't cause premature cracks. But they don't sink evenly very often. A membrane would/should help the concrete keep a little drier by virtue of the fact that it is not in constant contact with the wet and damp grounds that we encounter during our long and ardous winters. And thereby give every chance of aforementioned concrete to not crack.
It's up to you.
Not a lot of work involved in unfolding/unrolling some plastic is there ?
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True.
But it's a total waste of time and won't make the slightest bit of difference
A membrane is not just to stop damp rising.
It also prevents 'the fines/water from running into the ground- hence preventing the concrete from drying to fast and keeping its strength.
Also if you really want peace of mind- for what it costs-- put a sheet of steel mesh in the slab. It will help it all hold together . Sort of a mini raft.
It also prevents 'the fines/water from running into the ground- hence preventing the concrete from drying to fast and keeping its strength.
Also if you really want peace of mind- for what it costs-- put a sheet of steel mesh in the slab. It will help it all hold together . Sort of a mini raft.
That is complete nonsense. So much so it warrants a WTF!
Despite this being a concrete slab in the garden, and not the Hoover Dam, the evaporative rate from the open surface will be many times the absorption rate from the underside to the ground
Some people have standards. I am one of them.
Maybe you should read up on things woody . You may learn something.
What I say is correct. It's also the way I have done things for many years -with absolutely no complaints or issues with any slab I have ever laid.
What you say about evaporation rate being greater than ground absorption rate- is a load of bowocks.
Just because the slab is in the garden does not mean you have to make it inferior to one that is part of a building .
For the very small difference in cost-- between your way and mine -- anyone with any sense would choose my way.
Always belt and braces job for me .
This must be most amusing to the OP.
I think you should do your concrete slab half and half. Membrane under one half. Other half unmembraned with a movement joint inbetween.
Post back every 10 years and let us know which half is holding up better.
I think you should do your concrete slab half and half. Membrane under one half. Other half unmembraned with a movement joint inbetween.
Post back every 10 years and let us know which half is holding up better.
Doing something unnecessary and stupid for years does make it right or a good idea. And it's not exactly conclusive support of your proposition
Belt and braces is for people who have not got a clue, and just want to cover their lack of actual knowledge
Belt and braces jobs are done by people who take pride in their work and dont have to hide behind closed curtains every time someone knocks at the door.
Belt and braces jobs are done by people who have greater knowledge than the 'rag and tag bobtail' builders who are 'here one minute and gone the next' .
Daft thing is Woody -- the way I'd do it and the way you seem to do it is a difference of 10 minutes and £20 max.
A bit of visqueen and a 3.6m x 2.0m sheet of A142 reinforcing mesh (£20 max inc of VAT)-- gives peace of mind -- for YOU and for the client.
No need to leave your ans-phone on and curtains closed all the time !!.
That's the trouble with lots of cowboy builders- they tend to be cheapskates and all for the sake of a few £££s.(peanuts).
You may see it as 'overkill'-- but- seeing as the OP
does not want to dig out too much-- how do you know what his ground conditios are like ????????????????.
Also- I may add - I would also use a C30 mix just to make sure- -for the sake of £5-10 extra.
Consider also- the weight of the 1000 ltres and the weight of the tank- and also 'point loading' .
So- for the sake of £30 extra- peace of mind guaranted.
I rest my case .
ps- From piling, underpinning, rafts, deisgner slabs/foundations-- I have done them all buddy.
Bet you have never even heard of 'slab lifting technology either ??. (thats to cure the problem of inadequate foundations which have been laid on dodgy ground).
Look it up and learn something .
ps- also- realise- the weight of that particular full tank plus the weight of the tank will add up to having a pack and a half of concrete bricks (maybe more) sat on the ground. For many years.
You clearly have not got a clue.
The whole point of building is to design properly and build efficiently. Not all this £20 here, and £5-10 there to give yourself some piece of mind.
Just do it properly in the first place using what materials you need to use to give a value for money job to the client. Not charge for all the rubbish you want to include because you don't actually know what to do.
Can't say I see much polythene being specified or used under concrete slabs. Funny enough I don't see many concrete slabs sinking either because of no polythene underneath
Is slab lifting technology the same as Uretek ... the sole company in the UK to do this? Has their system got a BBA certificate yet, and do proper engineers like and recommend it yet? No never heard of it.
The whole point of building is to design properly and build efficiently. Not all this £20 here, and £5-10 there to give yourself some piece of mind.
Just do it properly in the first place using what materials you need to use to give a value for money job to the client. Not charge for all the rubbish you want to include because you don't actually know what to do.
Can't say I see much polythene being specified or used under concrete slabs. Funny enough I don't see many concrete slabs sinking either because of no polythene underneath
Is slab lifting technology the same as Uretek ... the sole company in the UK to do this? Has their system got a BBA certificate yet, and do proper engineers like and recommend it yet? No never heard of it.
Whatever you say Woody- you cant knock me- because I go 'up and beyond ' the requirements.
If I stooped below them- then you could make negative comments.
So- until then- take a step back and think before you pass judgement on my skills.
You do it your way and I will do it my way - 'simples'.
At the end of the day- it is just your opinion .
Do you have 'letters' after your name- ?. to say you are totally correct in what you say ?
Have a chat with a few SE's. They will tell you what is 'probably ok- but if you pay their fee- they will go 'belt and braces' everytime- to cover themselves.
Tell me- just what experience you have regarding such matters ?. Dare you ? Let everyone see .
C'mon - bud- -- and no excuses .
Aside from what I said on my last post Woody. Of course slabs dont sink because of Visqueen not being installed underneath. But- let me assure you- the concrete strength is compromised if the 'fines' and the bonding agent (cement) run away into the ground/ and/or the concrete dries too quickly.
You really need to take a look at concrete curing - requiring a steady hydration.
Anyway- these are things you should know by now- and if you want any more info- I will have to charge you.
All mouth and no trousers Woody .
Regards,
Pete
ps- before you ask- I DO have letters after my name .
You really need to take a look at concrete curing - requiring a steady hydration.
Anyway- these are things you should know by now- and if you want any more info- I will have to charge you.
All mouth and no trousers Woody .
Regards,
Pete
ps- before you ask- I DO have letters after my name .
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