Thin Concrete layer on existing concrete patio
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Thin Concrete layer on existing concrete patio

by jonhamil » Tue Jun 02, 2009 11:04 am


Please excuse my inexperience on these forums - everyone has to start somewhere!

I am selling my house and have a concrete patio which needs recovering - the drains have previously been dug up. If I were staying I would use paving slabs but since I am moving I need to keep costs right down - even decking is prohibitively expensive. To complicate matters further there is currently 2 brick courses between the patio and the DPC.

I am proposing to lay a 1/2" thick concrete layer over the existing base. My idea is to follow the following process:

1. jetwash exisitng patio.
2. Allow to thoroughly dry, then apply 1 coat of 4:1 dilute PVA.
3. Make up formwork to allow a 1/2" perimeter of concrete to be laid around the edge of the patio. PVA inside the perimeter with a 2:1 dilute PVA.
4. Mix up concrete and fill perimter allow to go off for around an hour.
5. Trowel up. Allow to dry overnight.
6. Remove formwork. Pva remainder of patio with 2:1 dilute pva mix.
7. Fill main area of patio with concrete and finish as perimeter.

Does this sound reasonable or does anyone have any suggestions how I can improve / likley problems I will encounter?

My main question is re. mix. With the layer being only 1/2" thick - how can I improve the concrete mix to avoid cracking? I thought about:
1. Plasticiser
2. Waterproofer
3. Adding lime to the mix, or using lime instead of cement.
4. Using a very high cement to sand ratio for strength.
5. Adding some kind of fibre to the mix
6. Adding a small amount of gravel to the mix.

I have little idea of what kind of ratios of sand/cement to use, or what kind of sand - any suggestions would be very gratefully received.

Many thanks in advance!


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by bd3cc » Wed Jun 03, 2009 10:06 pm

1. There should be 2 brick courses between patio and DPC
2. Concrete (ballast and cement cannot possibly be laid 1/2" thick)
3. The next nearest mix would be sharp-sand and cement and even this would need to be treated with something like Ronaflex(expensive) to have any chance of succeeding, particularly outdoors.
4. Seek out an independant manufacturer of paving slabs, as there is a vast difference in cost.(A recent patio I did 800, as opposed to 230).
5. When selling, any decent surveyor, will spot a bodge job and use this as a tool to renegotiate down.
So bite the bullet and do a decent job and you will sell quicker, and achieve a price.

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