A familiar patio question

[jamie Smith]

Hi all

I've read and digested a lot of the infomation out there on the web - most notably pavingexpert.com and also a lot of the posts on this forum regarding bedding mixtures. Thermo - who appears to know his stuff - recommends wet mortar as opposed to 10:1 a dry sharp sand/cement bed.

Having read the various responses, I too am coming around to the idea of a full mortar bed, laid over a thick layer or compacted soil, overlain by 30mm of compacted stone dust. My question is what sort of wet mortar mix do you recommend? Is it a standard 1:3 cement to sand? How wet does the mix need to be? Is a watery mix best for extra suction? any tips for getting the mortar bed level prior to laying? Any advice appreciated?

Thanks

 

[Thermo]

the best mix is somewhere around the ratio 3:2:1 or 4:2:1

ie 3 sharp sand 2 building sand and 1 cement.

As to the moisture content it very much depends on the thickness of bes and the type of slab you are laying. It needs to be workable, but firm enough to support the weight of the slab. Obviosuly a heavy stone slab will need a slightly drier mix than a normal concrete paving slab. It needs to be drier than a normal bricklaying mix.

You dont get the mortar bed level prior to laying. Lay the mortar over the area where the slab will be and then run the point of the trowel through it several times to create furrows. You then lay the slab on top of it and it should be slightly highe than the previous one laid. You can now gently tap it with a maul or rubber mallet with light taps across the corners and centre to get it level.

Work out the level of the patio at each end and lay a slab at each end. the slab that is at the end you will be working to is temporary as you wont know its exact position until youve laid the other slabs. it sjust there to give you your level datum. Now run a string line between them, which will give you your level and fall for the slabs to work to. Use a spirit level or a staright edge to check them as you go. The straight edge wont always be exact on very riven paving.

Dont rush it and dont keep faffing about with it once its laid. if the string line and the straight edge show they are right then they are right. The eye can b deceiving and you can get over critical of a few mm at eye level. remember you will be walking on the slabs and looking at them from 6 feet away.
hope it helps.

 

[jamie Smith]

Thanks Thermo, that's what I was after. It now makes perfect sense to me that a bedding material that dries hard and bonds to the underside of the flag - as opposed to slightly stiff sand - is going to give a better long-term result.

I'm not the type to get hung up on what my eyes tell me - I make maps for a living and was brought up to believe my instruments when they tell me west is west, east is east and never the twain shall meet!

Here's hoping for a dry day on saturday and a willing labourer (i.e. my best mate) to take care of my mixing.

Cheers again