Laying a patio

chabsey

My back garden is half covered in concrete. The surface is bad, uneven and flaky with dandelions coming up through cracks in the concrete. I was therefore thinking of putting down a small patio.

From what I've read all the guides say I need a base of hardcore, rubble etc. However, if I'm laying this on top of a concrete base (which is very solid, despite its ugliness) do I still need to create this base?

Thanks!

Irish Gardener

Hello chabsey.
You should be able to create your patio on your concrete provided......

1. There is adequate drainage from your concrete area, don't create your patio where water will lodge.

2. You treat the dandelions and weeds coming through the concrete with a translocated herbicide (Roundup)

Sonnenblumen

If the concrete is cracking and weeds are emerging that you would need to take a close look at the stability of the concrete. In theory you can build a patio on a concrete base providing it is is firm and stable and does allow water run-off form patio to drain away. So you will need to check the falls(concrete) to ensure it allows quick and easy run-off from patio.

Another aspect you will need to consider is the level change, and depending what material you patio material you plan to use (I would recommend you lay slabs on a wet mix base of sand /cement ratio 5:1 respectively on concrete base) you could end up with a height increment of 3" (80mm), 25mm cement and 30-50mm for slab. This is effectively the equivalent of half a standard step (150mm/6") and is a potential hazard. How you resolve this potential hazard requires some careful thinking both for the immediate area around patio but also the existing levels of the wider area. One relatively easy and cost-effective solution involves adding decorative aggregate around new patio, but pierece/drill in random areas concrete base (for drainage) before applying aggregate. Note here round aggregate is more cumbersome for walking on/wheeling barbeque units etc than the chipped aggregate which effectively lock-in when compacted.

As previous poster recommended, treat area with Roundup before commencing any work. Roundup must be applied during dry conditions and takes at least 4-5 days to take effect. You moight need to apply weedkiller on an annual basis (Roundup within the limitation mentioned is very effective, however Easyweed/Casoron G is even more effective). Can be applied (granular) directly from container, no mixing required, and during dry or wet conditions, ideally during October-April and provides effective barrier for up to 12 months.

S.

De_man

hi chabsey for general info

try the following link www.pavingexpert.com (excellent)
also use the search facility on this site for "patio" a lot of info here