Slate Tile Patio Sub Base

[engmpoll]

Hi

I have just moved into a new build property which requires the construction of a large patio, approx. 65m2. As we are moving near to a slate mining area in North Wales I have got the notion to be sympathetic to the surrounding area and use an external slate floor tile of approx. 10mm thickness from one of the local quarries. Obviously with a tile of this thickness, a solid and well thought out sub base will be required. I was thinking that a 100mm sub-base of compacted granular material based on ground conditions followed by 100mm of poured concrete, most likely in 2 – 3 separate pours to allow the construction of joints in the slab.

Does this sound like a reasonable plan?

I guess my main questions are as follows:

Would a 4-2-1 concrete mix be acceptable in this application or should I go weaker or stronger?

The largest single pour will be approx. 36 m2 (4 x 9 m) should I consider the inclusion of re-bar mesh or would a fibrous concrete be sufficient? Should I perhaps split this into 2 separate pours and add an extra joint?

That leads me onto my next question, do I go with a joggle joint or do I use a dowelled joint with one end de-bonded and Flexcell in between. Is one preferred over the other?

Finally, what is the consensus on a DPM, I see the pro’s and con’s for its inclusion. The problem I have is I can’t figure out what to do with the excess beyond the perimeter of the slab. My lawn will essential butt up to the edge of the concrete slab, should I just fold back the DPM on itself and trim to the height of the slab. How would I prevent water getting between the DPM and the slab and migrating underneath the slab?

Look forward to hearing your thoughts.

Cheers

Matt

 

[Ouch77]

try looking on this site:

http://www.pavingexpert.com/

There's a forum full of knowledgeable types there too. Not that I'm suggesting that folks here aren't knowledgeable, but those guys do paving day in, day out..

 

[r896neo]

Your sub base sounds fine.

4-2-1 is fine, weaker would also be fine.

Don't stress too much about the joint as long as you have one it will be fine. but remember you need to carry the joint up to the surface so will have expansion joints visible and breaking your pattern.

The dpm is not needed to keep water out but to keep it in while the concrete cures.

Personally i would save yourself a lot of heartache, money and possible problems and use slate flags. These can be laid on a 100mm sub base and then 50mm mortar bedding with bonding additives. It'll be cheaper and less to potentially go wrong in my opinion.