smart51
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posted on 20/5/16 at 08:09 AM |
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Concrete mix - volume or weight
I'm going to build a play shed in my garden for my son. It will need to be built on brick piers so its at the right level at the front, so
I'm going to dig a pit at each corner and fill with concrete.
Google suggests a 1:2:4 mix of cement, sand and aggrigate. Is that by weight or volume?
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joneh
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posted on 20/5/16 at 08:25 AM |
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Most footings I've done are a 1:4 shovel full using cement and ballast. Generally measurements are volume.
Can't see a builder with a set of scales!
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nick205
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posted on 20/5/16 at 08:26 AM |
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For concrete I tend to work by shovel fulls of each trying to get the volume roughly right (particularly when using a concrete mixer) then just add
water and a little Febmix (plasticiser) until you get the runny-ness (sp?) you want. From what you describe I'd imagine you want it quite runny
so it will level itself when the holes are filled. Be aware it may take a while to dry/harden before you can build onto it.
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Mash
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posted on 20/5/16 at 08:28 AM |
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For what you're building it's not massively important Mate, as it's not carrying huge amoun ts of weight, but this web site is
really useful:-
Concrete calculator
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Slimy38
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posted on 20/5/16 at 08:28 AM |
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I asked this exact same question a while back, and the response was 'put yourself in a builder shoes, what will you have available?'.
As joneh says, a builder won't be carrying a set of scales around on site, but he will have plenty of 'shovelfulls'.
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smart51
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posted on 20/5/16 at 08:46 AM |
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quote: Originally posted by Slimy38
I asked this exact same question a while back, and the response was 'put yourself in a builder shoes, what will you have available?'.
As joneh says, a builder won't be carrying a set of scales around on site, but he will have plenty of 'shovelfulls'.
I was thinking in 25kg bags, which is what I'd buy from the shop.
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smart51
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posted on 20/5/16 at 08:52 AM |
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quote: Originally posted by Mash
For what you're building it's not massively important Mate, as it's not carrying huge amoun ts of weight, but this web site is
really useful:-
Concrete calculator
Good site. For a 25kg bag of cement, it recomends 47kg of sand and 94kg of aggrigate. I reckon thats 1:2:4 in terms of volume, as it's a bit
less in terms of weight. As you say, it's not critical for my application.
quote: Originally posted by nick205Be aware it may take a while to dry/harden before you can build onto it.
Its a several weekend project. The concrete will get its 28 days to cure before the job is finished.
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on_eighty_runner
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posted on 20/5/16 at 09:10 AM |
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I did something similar with a playhouse and got in bags of cement, mixer and a trailer of gravel.
A lot of cleaning up and hassle
When I did a deck I bough bags of postcrete- a bag of dry mix you dump into your predug hole filled with water.
It's s bit more expensive but no cleanup and for a lightweight application is probably good enough.
Alternatively look around for a builder who is already working locally and set up for a job ask him/her.
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smart51
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posted on 20/5/16 at 09:16 AM |
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quote: Originally posted by on_eighty_runner
I did something similar with a playhouse and got in bags of cement, mixer and a trailer of gravel.
A lot of cleaning up and hassle
When I did a deck I bough bags of postcrete- a bag of dry mix you dump into your predug hole filled with water.
It's s bit more expensive but no cleanup and for a lightweight application is probably good enough.
Alternatively look around for a builder who is already working locally and set up for a job ask him/her.
Bags of post fix would only work out £20 more expensive, so probably not a bad idea. But there's a builder on site doing other work. He leaves
his cement mixer in the garage over the weekend. I've spotted an opportunity
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nick205
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posted on 20/5/16 at 09:24 AM |
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A good call if you've got a mixer available to you - that will save a lot of time and back bending!
I laid a concrete base for my shed a few years back. Probably spent as long barrowing and leveling the hardcore as I did mixing and leveling the
concrete. I set a slight slope on it to help any rain water run off it and it's been fine for 10 years now (the shed itself is crap, but cost
£150 so can't really complain).
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garyo
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posted on 20/5/16 at 10:58 AM |
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Most important is to make sure that shovel=shovel. Cement has a tendency to stack massively on your spade whereas sand, especially if dry, can end up
with half the amount. If you're not careful you can easily end up with 1:3 just through shovelling error.
[Edited on 20/5/16 by garyo]
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SteveWalker
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posted on 20/5/16 at 11:14 AM |
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I think buckets or half-buckets are easier, especially when loading up a mixer. Less twisting and lifting, easier to measure.
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cliftyhanger
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posted on 20/5/16 at 03:40 PM |
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Mixer and bags.....
should be easy, chop cement bags in half with a handsaw, 1 bag of sand, 2 of ballast (or whatever) will be close enough.
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Mash
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posted on 20/5/16 at 06:39 PM |
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Built a 10 metre long by 1.5 metre high double block retaining wall back in 2008.
75 mm cavity between the blocks, and a 1 metre x 200 mm foundation.
All the concrete was mixed in my mixer using the calcs from the web site I linked to, and I measured it using the trusty bag method mentioned by the
other guys.
It's still standing, hasn't moved an inch, and is holdin up the farmers field quite well
[Edited on 20/5/16 by Mash]
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mark chandler
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posted on 20/5/16 at 08:29 PM |
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1/2 bag of cement, 6 decent shovels of ballast and 1/2 bucket of water into my mixer produced a nice strong concrete slab.
If mixing up for pointing/brick laying then you need to be precise for the same colour mortar across the job.
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smart51
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posted on 22/5/16 at 07:44 AM |
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It' sd one. Thanks every one. I put two bags of aggregate and one of sand in the mixer and it looked very stoney. I was a bit worried by by
the time it was lured it was great. I under estimated quantities somewhat. Probably because the sandy, cement and water fills the voids between the
stones. Two of the brick piers are built -and level with each other! I'll odo the other two this afternoon.
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