Wet or dry mix mortar for patio

baron777red

I am laying slabs to make a patio area, about 11 Square mtrs, this is the first time I have done this, and im not sure whether to use a wet or dry mix for the mortar bed.

I have read various forum posts, and most are saying a damp mix at a ratio of 9:1 for sharp sand and cement, is this ok or should it be less.

The thing I am worried about is how long do I have to work with the mix before it sets, I won’t be using a cement mixer, so will mix in in a big tub,

Or would a dry mix mortar bed work? Ive read the easiest way to do this is to put the sand down, level it, and sprinkle the cement over it, to a ratio of 9:1 then rake it through a few times, and then lay the slabs, and it will set within 24 hours using the moisture in the ground and in the air.

This dry mix seems a lot easier than using the damp mix, and would take a lot less time.

Another thing im not sure on is the spacing to leave in between the slabs, 5mm or 10mm.

For the pointing, I was going to leave the slabs to set for 24 hrs, and then do another mix of damp mortar, with ratio of 3:1 sand/cement, is this ok.

I would appreciate any tips,

Thanks
Colin

saverbuyer

Best site around for this sort of thing


http://www.pavingexpert.com/

Ebe_Scrooge

In theory you can lay a dry mix, and it'll absorb moisture from the ground and set. The problem you sometimes get is that the bottom gets damp, forms a skin, then the rest won't get wet, so it won't cure properly.


Personally I like to use a normal wet mix - this also makes it easier to squish the slabs around to adjust the spacing and levels if needs be. Make the mix wet enough to be "squishable", but not so wet that it sags under the weight of the slabs.


Mix the mortar in batches - it should remain workable for a good 20 minutes or so, depending on the weather, but just make up batches as you go along.


For the pointing - again, in theory you can use a dry mix and use a watering can to wet it afterwards. I find it easier to make up a fairly dry "biscuit crumb" mix with just a small amount of water. Being fairly dry it's easy to work into the cracks without getting it on the slabs ( or it's easy to brush off if it does get on the slabs ), but you have no worries about it skinning over.

southcoastrgi

If you are going to use dry then it should be a flat bed which isn't easy to get a fall on it, I prefer the wet dab method one in each corner & one in the middle & tap them down with a rubber mallet

andyhop

southcoastrgi wrote: »

If you are going to use dry then it should be a flat bed which isn't easy to get a fall on it, I prefer the wet dab method one in each corner & one in the middle & tap them down with a rubber mallet

You don't spot fix slabs, you need a solid bed of mortar to ensure your slabs don't crack

Spot fixing also allows weed growth and insects to penetrate

southcoastrgi

I'm not the only one, but then I think she should used a wacker plate

https://youtu.be/lvsFCwQNH6w

andyhop

southcoastrgi wrote: »

I'm not the only one, but then I think she should used a wacker plate

https://youtu.be/lvsFCwQNH6w

Paving expert and all the major supplies of stone and slabs state no spot fixing . It's a bodge

baron777red

thanks for the replies, i think i'll go with the dry mix for the mortar bed at approx 30mm thick, get it level the sprinkle the cement on and rake it in. i am going to leave 5mm gaps in between the slabs, and then do the pointing the next day.

thanks

wrightk

southcoastrgi wrote: »

If you are going to use dry then it should be a flat bed which isn't easy to get a fall on it, I prefer the wet dab method one in each corner & one in the middle & tap them down with a rubber mallet

This is exactly how NOT to lay slabs

if your slabs are porous which a lot are to a certain degree you will see horrible spots on the slabs where you have dabbed underneath particularly when the slabs are wet, furthermore dabbing the slabs leaves them totally unsupported inbetween,overtime causing them to crack and collapse

By far the best method of laying is on a well supported sub base of mot type 1 sub-base (at least 75mm thick) and then laying the slabs on a wet mix of 3 parts sharp sand to one cement, creating a mortar mix

brightontraveller

Dry mix has its advantages but summerish, uk for a patio they don’t really come into it do it...... Wet

andrewf75

I did endless research on this and was told a moist mix is the way to go i.e somewhere between the ones suggested so far! just wet enough so you can squeeze it into a ball.