ReadiMix vs. DIY

[David WE Roberts]

Just doing the sums for the concrete 3.5 cubic metres.

Previously on this channel some people recommended just getting a mixer in and doing it by hand. I also asssumed this was a viable option if I wanted some extra exercise (I have worked big site mixers in my youth).

Eastern Concrete mix on site C20 mix (pay for what you use) estimate £386.

Using

to estimate raw materials:

Jewsons:

52 * 25kg bags cement £210.80 inc. 7 bags ballast (2/3 cu metre) £296.10 inc. Total £507.90 inc.

This does not include the mixer hire which is likely to be another £50.

I could reduce the cost of the ballast by having a bulk tipper load, but do I want a tipper backing up onto my block paved drive?

Also, the mix on site company extimated 45 minutes to barrow the 3.5 cu.m. (which seems a trifle optimistic to me for a single barrow, although they suggested that the driver might help). Anything above 90 mins would cause them problems with their schedule.

I am now wondering how much effort is required to level and tamp the load as it is barrowed through.

Does the team think this time frame is reasonable?

Cheers

Dave R

Oh, and there is another blast of cold air, frost, sleet, snow etc. forecast for the next few weeks. Not the best weather for laying concrete or building block walls.

[David WE Roberts]

A quote for ReadiMix (mixed at the plant) was £348.60 so an additional £40 to get the precise volume required does not seem unreasonable.

[David WE Roberts]

Oh, and does the team think that C20 is a suitable mix for a 100mm concrete slab with some reinforcing steel included? Perimiter of the slab (400mm all round) to be 200mm thick to support the single storey dense concrete block walls.

[David WE Roberts]

Gah! This and other calculators extimate a greater volume of ballast than the volume of concrete!

I can see that the water and cement powder will fit between the gaps of the sand and aggregate so the volume will be less than the sum of all the individual parts but how does the ballast manage to shrink?

[Tim Watts]

On Tue, 26 Jan 2010 12:18:55 +0000, "David WE Roberts" wibbled:

Rule #1 - Do not go to Jewsons. Rule #2 - Do NOT go to Jewsons. etc

A C20 mix for 3.5 m3 will be

around 5 x 800kg bags of 20mm gravel @ 40/bag = 200 and around 2.75 x 800kg bags of sharp sand @ 40/bag = 120 so ballast = 320 inc VAT

and I make it 45 x 25kg bags of cement @ 4.68/bag[1] = 210

Total cost = 430 inc for materials.

[1] This is for this product:

Circle Mastercrete Original (Plastic Packaging) Grey 25kg

I think it's worth a little extra for the plastic bags - you can store them outside without fear of rain messing up the cement.

All those prices were B&Q. At least print off the web pages, scribble the ex-vat price next to each price and take it into the builder's merchant to beat them over the head with. Do not leave without at least a price match. You might be better with a smaller chain too - more likely to be amenable.

I took my figures from here:

'd best double check the calcs.

Personally, I would take the gravel and sand separately. It's not a big hassle to take X shovels of one and Y shovels of the other and it's easier to find uses for left over sharp sand (mortar, screed etc) and gravel (drainage, flower bed dressing) than it is for ballast. But if you do go for ballast, price should be similar.

As for the mixer, one of these will manage:

are electric versions too - I own a second hand one of about that drum size).

You probably considered this, but don't bother with the silly little tip mixers - too weedy.

HTH

Tim

[Tim Watts]

On Tue, 26 Jan 2010 12:33:19 +0000, "David WE Roberts" wibbled:

C20 is a pretty decent general purpose mix - It's what I use by default for slabs.

[dennis]

I can see that if you have a pile of ballast and then vibrate it to remove the air it would be a smaller volume but I have no idea by how much.

[Anna Kettle]

Specify that they dont come on your drive. They might charge you a little more but I would think it worthwhile to minimise the amount of hard labour involved. That is what machines are for

but what I really want to know is ...

What are you building?

Anna

[dom]

For two barrows/barrowers, and no snags - doable.

For one person that sounds a bit of a heavy workout.

You know how easy/difficult your site is, how long the runs are, whether there's room for two barrows to cross each other on the paths etc.

I hate it when I get my concrete less than perfect. It stares back at me for ever after and smirks "I'm a rock now, and you missed your chance to make me perfect".

So I've probably made up my own - and had my own time frame to sort out snags, when readimix might have made it a bit less effort.

[fred]

In article , David WE Roberts writes

No contest, this is the way to do it, it's quick, easy and isn't expensive (that's not a bad price). Make sure that they are going to use a sealed auger mixer rather than a drum mixer with manual feed, that way the mix is guaranteed consistent and to a standard (a poster here has complained bitterly about a company that skimped and gave him a bad mix on a manual mixer).

They use oversize barrows and will move faster than you would think possible. The barrows will be hugely heavy so the runs must be planked for them to move at all, they won't move over soil or gravel, even if even compacted. An auger mixer will fill a barrow in seconds.

You'll just be doing a rough spread and level with a shovel while they are barrowing, you can do the fussy stuff after they've gone. Try to lay planks (scaffold boards) to get the barrow loads to where they are needed, moving them as necessary, then you are just doing a bit of spreading. Get a helper if you can.

Btw, I'm assuming that your 200mm strips will also have reinforcement at the bottom so that they will be 50mm - steel - 100mm - steel - 50mm, the top steel being your slab piece extending over the strip parts.

[Tim Watts]

On Tue, 26 Jan 2010 12:18:55 +0000, "David WE Roberts" wibbled:

Skip lorries haven't done mine much harm - provided they put wood under the jacks. But YMMV so to be safe, keep it in the road. Or accept you may need to lift a few blocks and resand and relay. Which is less effort for you?

I think you'll be dead if you try and do 3.5 tons single handed in 90 mins. That's about 50-70 barrow loads. How far away is the base from the road?

If you can get people to help, minimum 2 barrows/barrowers (assuming the load isn't going too far) and you on the base distributing, ramming and levelling it.

If you're short on fit/willing mates, a labourer will cost around the 70

+/-20 quid mark for a day cash - hire 2, it will be worth it. You can trust labourers to barrow stuff[1], but you should stay on the base so you can see and be in control of the laying. Then one of them can clean up and the other can assist you with levelling and tamping across the width (that won't work single handed) [1] Some labourers have many good skills but you have 5 minutes to find out or mess up your job, so it's simpler to assume no skills for this sort of project.

Find some other jobs for them to use up the day, like digging the garden or something. You may even find people who'll do a half day for cash too

- you don't need skills, just fitness and lack of pikiness. And enough reliability not to blow you out. At least if you hire 2 you might just get by with one if the worst happens, but it will be pretty hard work.

Have you given thought to frost protection, either as an additive to the mix (ask the company if you use one) or suitable covering material?

[Tim Watts]

On Tue, 26 Jan 2010 14:00:01 +0000, fred wibbled:

Oh - did I read it wrong - the mix company does the barrowing?

Never seen that before - but if so, take it - it will make life very simple.

Still need a mate to help with tamping though IMO.

[fred]

In article , Tim Watts writes

IME, mix on site they barrow, pre-mixed, delivered by concrete truck, they drop & run (unless agreed in advance and waiting time is paid), they wont wait long enough for you to barrow & pour.

[Phil L]

to estimate raw materials:

Readymixed is the only way to do it if the quantity required is over 1.5m3, but if you do decide to mix manually, I suggest you don't bother with the bulk bags and get the aggregate tipped loose - it's about £22 per tonne, compared to £35 per 800kg for the bags - look in the local directories for 'grab services' for good prices on stone, sand etc and BTW, 52 bags of cement is way too much - don't forget, you only need to calculate the sand to cement ratio - the stone is irrelevant, so as an example, if you were doing a standard c20 mix of 4:2:1, with your calcs above, 7 bags of ballast would contain 800kgs each, a third of which would be sand and the other 2 thirds stone, so you would have 1866kg of sand. Putting 1300kgs of cement in this is overkill, you would only need about 36 X 25kg bags, but as I said, readymixed is the way forward, and don't worry too much about the weather, laying it in this weather makes for a stronger slab than laying it in summer when it dries out too fast. Just make sure your shuttering is solid, you've got a decent spirit level and a few long, straight tamps ready and some good wellies and a rake.

If you are worried about your paving, lay a long sheet of visqueen from the pavement to the slab because they *8will* spill concrete from the barrows, and don't expect it to take all day neither - 2 men can shift 4 cubes of concrete in less than 40 mins and they normally have a driver and a barrowboy, so if you can get another barrow and someone to give you a hand, you can lay while the other two barrow, in which case, leave your mesh out until last, then drop it onto the filled slab and knock it down with the rake to the required depth ( you'll have at last a couple of hours to play with it in this weather), and don't worry about frost - concrete heats up as it's setting, so unless it's a very deep frost it won't have any effect.

HTH

[Tim Watts]

fred wibbled on Tuesday 26 January 2010 16:09

My only experience was MixaMate - one bloke on the back of a specially designed truck with integrated mixer and water tanks. No chance of him barrowing. He could however mix as fast as 2 blokes shovelling and ramming (it was being dropped direct into one corner of the hole) and 1 bloke checking and levelling could go!

[David WE Roberts]

** Unfortunately I have priced around the other builders merchants and they are more expensive. Our local merchant is Travis Perkins and they seem to charge more because they are the only local merchant. Jewsons is about 10 miles away but cheaper. Prices improve and delivery is free if you open a 'Self Build' trade account. **

Watts - please see me after school for remedial maths.

200 +120 = 320 320 + 210 = 530.

Although even at your £430 it was more expensive than the mix on site option.

[David WE Roberts]

You didn't misread my original post - see above.

Plan is for me to run the barrow as the fittest and one with the most barrowing experience (although there are not a lot of major challengers for either title). Our friend (who is now recovered from the quadruple bypass) and my Lady Wife will be spreading and levelling the concrete as I hurl it into the pit.

I saw an estimate of up to 70 barrow loads - the run is to the end of my garden from the road and 30 seconds each way is going some over an hour and a half.

So I suspect that if things are going slowly and the mixer bloke sees his day getting a lot longer then he may well run a few barrows himself.

Extra scaffold boards have been purchased so that the run across the lawn will be on wood.

I also plan to have a board down into the pour area so that I can get to the far side. I expect to fill in one area on the side nearest the road, then use this as a platform (with suitable boards) to work my way outwards from my initial area until I have filled the whole thing. I will obviously have to have all the boards etc. laid out before the mixing starts to be able to manage a quick transfer from lorry to site

Always assuming we are not in for another couple of weeks of ice and snow.

Cheers

Dave R

[Phil L]

Spreading and leveling is not a suitable passtime for anyone with a history of heart problems - seriously - I wouldn't allow him near the thing

unlikely as he has to operate the delivery mechanism himself, you'd be better asking if they do a barrowing service - most do at the rate of a few quid per cube, you'll probably pay £25 to have it all barrowed in.

you do all around the sides first, then work your way to the middle, then out through the part you've been using as an entrance, this way you can get either side level, and put a long timber across from one patch to the other and get them level with each other, then it's just a matter of filling in the gap

Most readymix arrives already mixed - the measured stuff which mixes via a screw type contraption are notorious for stopping halfway through and announcing that you've had your quota, whereupon you have to argue and eventually give in and pay for double what you originally ordered

[David WE Roberts]

Given that he helped me dig out the site and barrow everything into the skips I think your expert medical concern may be misplaced. We are all sensible adults and aware of most of our limitations.

(a) Not likely to happen as they have done quite a few deliveries around here without any problems. (b) Yeah, right. Never going to happen. If the slab is only half full they have no chance of claiming they have delivered the full quota. Besides, how is this different from RediMix delivering a load which is under the ordered volume?

Sadly, I am starting to question the value of your advice.

[fred]

In article , Tim Watts writes

See my original post for the suggestion of only using an auger mixed setup for site mixed concrete. Huge truck turns up, guy pulls a few levers and mixed concrete pours into barrows like a visit to Mister Whippy. Driver and mate doing the barrows, job done in no time. Can't remember the outfit.