Carport slabs - Bedding mix

[Richchad]

I am going to lay about 24 Sq Metres of Lonstone Cobble Slabs 450 x 450 under a carport.

I have about 100mm of sub base consisting of crushed broken concrete pieces mixed with sharp sand, this was laid originally under gravel for car parking and seems fairly well settled.

I am intending to do a 50mm wet mix, say 4 sharp sand/building sand mix to 1 of cement rather than a dry 10:1 bedding mix, does this all seem okay?

[lutonlagerlout]

does this all seem okay?

no not really,building sand is not really upto it. its too soft
i'm not sure of the slabs you are using but i would normally go for 100mm bedding layer under any vehicular area (wet)
base sounds ok but obviously needs to be vibrated to fill any voids
risk it for a biscuit?? as they say
regards LLL

[Richchad]

Thanks for that LLL, with regard to the wet mix, I was going for a 70% sharp sand, 30% building sand mix to 1 part cement mix, if building sand is too soft what mix would you recommend?
Maybe a 5 sharp sand to 1 cement mix?
I will increase the bedding layer nearer to 100mm which should help

[lutonlagerlout]

if you are going for cars on it really try a wet concrete mix,its a lot more fiddly but loads stronger,although i am not familiar with the slabs you mentioned,i know a dash of building sand improves workability for patios but cars put a lot more strain on the area
cheers LLL

[Richchad]

Okay LLL will do a wet mix but can you help me to clarify the mix, the calculators tell me to cover 24 Sq Metres to a depth of 100mm I need about 4 tons of sand...but which type of sand and how many 25Kg bags of cement?
Sorry to keep hassling you but need to order ASAP and have to decide on the mix ratio and which sand.

[lutonlagerlout]

its no hassle richard
4 tonnes of ballast and 20 bags of cement
i say ballast you could try flooring sand but this isnt as strong as ballast,but its stronger than building sand
if you get my drift
cheers LLL
ps i always use a glug of pva in every mix

[Richchad]

4 tonnes of ballast and 20 bags of cement

Oh, so Ballast then at an 8:1 mix, not Sharp sand mix, but thinking about it I guess I need concrete under the slabs rather than a mortar mix. Thanks for your help LLL.
My BM supplies WG Ballast...anybody any idea what WG stands for ??? ??? ???

[lutonlagerlout]

My BM supplies WG Ballast

havent got the foggiest old chap???
regards LLL

[TheVictorianCobbleCo]

My sixpence worth - 1st, the thoroughly compacted sub-base, then the frame surround and 4 inches (100mm) wet concrete 8:1 with 3/4" ballast, screeded with wooden straightedge. The slabs, if I'm right are about 30 -40mm thick, and need to be FULLY supported on a stone free pug, I normally use a combination of sharp and building sand, with PVA added - I'm nervous about putting a car on these slabs though, and welcome being shot down by the more knowledgable guys, but be warned.
Good Luck
Billy

[bobhughes]

A good concrete base is what's needed. 24 metres is small enough to lay as a single slab (no need for expansion joints) so no hassle there. Remember the slabs are really only decoration (like wallpaper). It's the base and sub base that do the work.

[Richchad]

Thanks for all the advice guys...Slabs came Friday, have now laid all except where need to cut round manhole cover and a drain :;):
When the slabs arrived they were much pinker than in the brochure...yes I know we should have looked at the actual slabs before ordering...anyhow decided to go ahead rather than wait to change them.....they don't look too bad and it is only a carport, not a patio...however just a thought is there anything on the market that would colour them or maybe tone them down a bit

[seanandruby]

mother nature. ???

[Richchad]

Very good.. :laugh:
Trouble is it will take ages as it is under a carport

[mouldmaker]

You're best advised to let nature take it's course. Even in a car-port the colour will have mellowed significantly in 12 months or so.