Riven slabs fitted on building sand - Need your advice - urgently

[The-oracle]

They are Riven slabs. Bought from Wickes and supplied directly by Marshalls. Sizes varry between 860 x 560 and
560 x 560 and 560 x 270 and 250 x 250

[lutonlagerlout]

sorry for the confusion
riven SLABS are made from concrete
riven FLAGS which is what you have are natural stone
did he use any subbase under the sand cement bed~?
i.e. hardcore or type 1 stone?
cheers LLL

[The-oracle]

did he use any subbase under the sand cement bed~?
i.e. hardcore or type 1 stone?
cheers LLL

NO none

He laid straight on the sand & Cement bed

Is it essential to have an MOT1 under stones?

[Suggers]

Yeah - but what did he lay the bedding mix onto? - levelled, compacted subsoil - you must have seen it?
ps - I'm with LLL on this one, don't do anything rash -

[The-oracle]

He laid it straight on the soil (he compacted the soil after taking out all the vegetations).

[The-oracle]

Just to update you guys
I got a pro to redo the job now.

He removed all the slabs, cleaned them, digged out the previous bedding, laid 25mm of MOT Type1 subbase & compacted it. Tomorrow he'll lay the patio on a Sharp sand & cement mix (semi-wet mix), then he'll do the bonding at a latter stage.

He is charging £800 for a 24m2 area (not sure if the price is right, but I feel like he knows his stuff and he's listed on the Marshall's website as one of their recommended contractors).

The work also includes replacing a manhole with a recessed one filled with flags and laying and compacting 25mm of MOT type1 subbase over another 20m2 in preparation of laying some artificial grass.

Your thoughts please

[lutonlagerlout]

whats the point of 25 mm of MOT type 1?
none
needs to be dug out and 100mm compacted type 1 installed
LLL

[The-oracle]

OMG I am sorry
It is indeed 100mm, I need to go back to math school

I brought in 5 tonnes of M.O.T Type1 for a 24m2

[lutonlagerlout]

5 tonnes bit on the low side for that,24m2 needs about 8-10 tonne to get 100mm thick
LLL

[The-oracle]

5 tonnes bit on the low side for that,24m2 needs about 8-10 tonne to get 100mm thick
LLL

Not according to the Calculator on this site

I used it as aguide as to what to order, and it told me go buy 4.8 Tonnes

[Rich H]

Bang on. Although, I work on 1tonne/7 sq.m at ~70mm depth which is all you really need for a sub-base for domestic paving. 100mm + 50mm (or so) sharp+cement + 50mm (or so!) slab = 8 inches of solid stuff. Surely OTT for a back garden job?

[lutonlagerlout]

sorry oracle
looks like i completely lost the plot there?
it is indeed about 5 tonnes
i havent got a danny where i got 8-10 from
??? ??? ???
ahem
LLL

[The-oracle]

sorry oracle
looks like i completely lost the plot there?
it is indeed about 5 tonnes
i havent got a danny where i got 8-10 from
??? ??? ???
ahem
LLL

lutonlagerlout
I got my math wrong myself when I suggested a 20mm subbase :;):

And Rich H you are right, even the 5 tonnes did not get me the 100mm, I got circa 80mm after compaction with a wacker, which is - as you said - enough for a rea patio.

[Stuarty]

Remember you wont ever get a tonne from a merchants, in the bulk bags anyway. You order 5 bags and your about a half tonne to three quarter shy in weight

[lutonlagerlout]

i'm pretty sure minimum subbase is supposed to be 100 mm when compacted,but in the real world of barbecues and kids playing its unlikely to move, and is a damn sight better than no subbase at all
sounds like your on the right track now mate
good luck
LLL