Mortar bedding thickness

[mo-uk]

Further to my previous thread which can be seen here:

http://ext.pavingexpert.com/cgi-bin....t=12839

I took up my old patio and I removed all of the old base (huge amount of work). In the end I decided to do it msyelf due to cost.

I comapcted what was there and took the view it was hard enough to withstand a new patio.

My problem is that the height of my compacted surface is a fair bit lwoer than my final level. I know ideally you would get more sub base material like type 1 and make up levels but I vae decided to just make the mortar bed slightly deeper.

My overall mortar level is about 8 to 10cm.

I note the site generally only mentions the bedding going up to 5cm.

I have laid 2 test flags with a semi wet mix (4 sand, 1 cement, half bucket water). I am finding that it is VERY hard to adjust the slabs once they are on - and with enough hits I start to get water coming to the surface which causes even more problems with tryign to stop staining.

As far as I can see I have 2 options

Make the mix dry so water doesn't come up - my problem is all my flags vary in thickness so trying to pre-deterime the ideal height of the bed each time will be a pain. I udnerstand a dry mix has less give with a hammer/mallett.

An alternative is that maybe 10cm of bedding at once is making things harder and I could be better off putting down say 5cm of material and let it dry and then come back and do the final lay with another 5cm - would this make it easier?

I appreciate I could just get 5cm of type 1 but problem is I have all the materials now.

[London Stone Paving]

I would seriously consider biting the bullet and getting the extra Type 1 in. Your going to be using a barrow full of mix per slab!!! As a DIYER you need to be focussing all your efforts on building a nice patio, not mixing an endless supply of mortar

[r896neo]

bedding that thick turns to soup when tapped too much. consider adding some 10mm graval to make a fine concrete.

As steve said though get more type 1. The amount of extra money you will spend in sand and cement will pay for it.

[mo-uk]

OK in order to make up say 50mm I have 3 options.

I already have 3tonne of grit sand on site which was going to be sued for my bedding mix - its in a position which makes delivery of more materials awkwards - certainly loose dropped as opposed to bagged.

Options are

1 - use the grit sand and make a 4:1 mix as a base

2 - get aggregate and make the base out of concrete

The disadvantage with the above is I suspect the cost of the cement. I think I am right in saying a 6:1 concrete mix will be strong enough and will save cement voer a 4:1 sharp sand/cement.

3 - get MOT Type 1

The downside with this is I will have to get a plate compactor and have it available for a few days - it also puts pressure on me to get it done quicker - whereas if I do optio n1 or 2 I can do it in my own time. A weeks hire on the compactor plate is say £45 - I need to hire it anyway for a day at £25 for I am talking £20 extra which is say 6 bags of cement.

Generally does a cement/sand mix or concrete work out more expensive than type 1 for a base?

[r896neo]

Yes because of the time required to mix it also.

6:1 is plenty strong enough for a grit sand bedding mortar.

Shifting in 3 bags of mot and compacting it is at most a couple of hours work, maybe 3 if it has to go a long way.

Dont know why you'd need the plate for a week.

[mo-uk]

I should say I am doing it a few afters work per night.

If I did type 1 I would bring a bit in, flatten it, bring more in, flatten etc and so on til I got my levels perfect.

I suspect it is doable within 2 evenings so that is probably what I will do.

[London Stone Paving]

I would strongly recommend the MOT route.

Creating a 4:1 mix as a base COULD have disastrous consequences for your patio. MOT is permeable where as a 4:1 base mix would not be. After you have laid the paving all the moisture from the bedding layer will need to go somewhere. It will take the easiest route which will be straight through your paving material. On its way through it could drag through cementitous material and cause a horrible leaching effect.

I've experienced this exact issue when I had my front garden paved a couple of years ago.

I got home expecting to see a finished patio and the landscaper must have had a complete brain fart because the paving was 50mm below the required level. Rather than get him to remove the bedding layer and build up with MOT I was stupid and we decided to lift the paving and re-lay on top of the bedding layer

For the next year I had loads of horrible leaching on the paving. Not good.

Why risk it?

[lutonlagerlout]

why do the feck ups always happen to those in the trade at their own house?

I reluctantly agreed to overlay a concrete area for a client and the same thing happened

picture frame heaven,every flag had a white picture frame for around a year due to the subbase being impermeable

LLL