The Brew Cabin

I have a Victorian Semi with front garden containing a small grass area (3m square) surrounded on 3 sides with earth borders with shrubs in. The 4th side is the path to front door.

I've dug around the edge of grass and borders/path and laid in some quality Victorian rope edgings in a bed of concrete and haunched in.

The area enclosed by the rope edging is thus is 3.1 m square (i.e 3 m square for slabs with bit more for pointing room betwen slabs).

Now I want to remove the grass/earth inside the 3.1 square and lay 600mm sq. riven paving slabs - 37mm thick.

Now the questions Tony et all:

- after digging out grass/mud do I need to lay any geo membrane down or weed kill to stop plants rising?

- how deep do I excavate the grass/soil to i.e what thickness of bedding material

- what bedding material do you suggest

- do I need to compact the soil once excavated and do I need to compact the bedding material

The paving area will only be used for putting flower pots on and sitting on (no cars) :)

Anoher question is that do you recommend pointing by sweeping in the mortar dry and spraying with atomiser?

Only last time I "wet" pointed it stained the slabs and was well fiddly!

Sorry for such big list.

PS for Tony - I thought the road base, not sub base, carries design weight in roads/pavements?

Best Rgds

Mark

All the answers to your questions are on the main website. There's a FAQ on whether a membrane is required, and then the Laying Flags page deals with the bedding requirements and laying details. Once you've got the flags laid, there's a lot of advice on Pointing in that section. The atomiser idea is a bit of a nonsense and is best avoided.

On your technical point, it can be argued that a road base carries the loading of a road/pavement, but, as much of this website is devoted to lightweight pavements rather than roads and highways, there isn't a lot to be gained by introducing discussion on construction layers that are often omitted in the type of pavements under consideration. Personally, I still believe the sub-base is just as vital in ensuring pavement strength as is the road base. As sub-bases are present in more pavements, it makes more sense (on this website) to devote more attention to sub-bases and leave discussion of road bases to those areas where higher traffic levels are expected.

Roger Tony re FAQ and pavements. Understood over and out ... except....

Re dry pointing..... where does the moisture come from if you lay flags on dry bed?

Mark

I don't like dry grouting/pointing, and although there is some discussion of it on the website, it is there for the sakle of completeness, not as a recommendation.

However......a dry grouting mix will draw moisture from underlying materials, whether that's the bedding or the sub-grade, as well as from the pavers themselves and even the atmosphere. The big "but" is that there isn't sufficient moisture available to achieve a satisfactory water:cement ratio, and so you end up with a drastically weakened mortar. Fairy Nuff, your flags aren't stained, but the jointing is a waste of time and materials, in my opinion!

When it comes to laying on a SEMI-dry bed, there should be enough free moisture in the bedding sand to initiate hydration of the cement content, and, because we are only looking for a low-strength binding agent rather than a tough, hard "concrete", an ideal w/c ratio is not required. The key point here is that it is not a dry mix on which the flags are laid, but a semi-dry mix - there is some water present, unlike the suituation where a dry grout is used.

Sorry to labour the point Tony.... how do you lay a semi dry bed?

I assume you mix up sand cement bed with a really low water content?

Or can you just spray the dry bed with fine water sprinkler?

TIA

Mark

There should be sufficient mositure in your grit sand to allow it to be mixed with the cement without needing to add any additional water. However, if your grit sand is particularly dry for some reason, or if you're adding gravel to the recipe, then some water may need to be added, but it should be kept to an absolute minimum. The usual rule of thumb is that, when you squeeze a handful of the mix, it should clump together but no water should escape - ie damp, but not wet.

Thanks Tony.

After reading your replies I'm going to lay a dry mix and bite the bullet and point with firm wet grout rather than dry grout.

Mark



(Edited by Mark H at 2:37 pm on Sep. 21, 2003)