The Brew Cabin

Posted: **Thu Jun 04, 2015 4:07 am**

I'm a DIYer creating a 25 sq.m patio using 28mm concrete pavers, intending to use a 40mm 10:1 grit-sand:cement bed with no added water. The sub-base is a concrete slab so does not require compaction and has no interstices to fill.

Collecting info from various pages of Tony's instructions, I see that:
1) A light pre-compaction of the bed using one or (at most) two passes of the compactor is recommended (or stamping with the feet!). (screeding.htm#prefer)
2) A 10:1 mix is more tolerant of incomplete compaction than pure sand, so is recommended for DIYers. (layflag3.htm)

Although renting a plate compactor isn't expensive, the fact that I'm a DIYer working slowly, that rain happens and that I'm using cement in the mix means I can't do all my compaction in one go. I'd need to repeatedly rent the wacker to do a bit more.

But I do have a lawn roller. So my question is this: given that a 'light compaction' is required and that the 10:1 mix allows some leeway with compaction, is the garden roller likely to provide sufficient compaction in my particular circumstances? If so, how many passes should I use?

Posted: **Thu Jun 04, 2015 7:21 am**

If you are using small block paving then yes I suppose a heavy garden roller should suffice. I'd go a bit stronger on the mix though at least 8:1 and maybe some water depending on moisture content of the sand.

What make is the paving 28mm seems very thin.

If you are using flag/slab type paving you may need to use a different method depending on how regular the thickness of the slabs are.

Posted: **Thu Jun 04, 2015 8:58 am**

Thanks Lemoncurd,

Well spotted on the thickness - it's specified as 32mm. Sorry for my mistake.

Specifically these are 450x300 slabs, Bradstone 'Aged Riven'.

(https://www.bradstone.com/products/trad ... en-paving/)

Posted: **Thu Jun 04, 2015 6:36 pm**

Personally I would use a different method for pavings of that size, you may find that tolerances in the slab thickness will make them difficult to lay on a screed bed.

Best to lay a bed for each slab as you go working with string lines and straight edges. Try a semi-dry mix or a wet one and see which you get on with best.
My preference is a wet mix, when you tap the slab to level the mix spreads out evenly and gives a fuller bed, and sticks better.

Posted: **Thu Jun 04, 2015 9:41 pm**

amen to that mark
I only ever use a semi dry on council greys
LLL

Posted: **Fri Jun 05, 2015 9:47 am**

Thanks again Lemoncurd, and LLL,

I'm going to use the method you suggest. It has the added bonus that it will allow me to do the job in small steps as I'll only be mortaring on an as-required basis instead of committing to a larger area. For an inexperienced DIYer this is important. It took me well over an hour to lay my first 5 slabs yesterday (only 190 to go!), and today it's raining.

I'll have to work on my technique to get a bit faster and to bed the entire area of the slab without mortar squeezing up between the gaps when I tap it down.

Posted: **Fri Jun 05, 2015 6:06 pm**

Where the mortar bed meets a joint rake a small furrow out along the edge of the already laid slab. The mortar should spread to fill the furrow without hopefully filling the joint.
Any excess rake out with your finger (gloved) or something.

Getting the bed right can be a pain, but if you get it roughly there and scoop out a dollop from the center for the bed to flow into as you tap the slab down.

The Brew Cabin

Using a lawn roller for bedding compaction