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I am in the process of planning for a deck. I have the deck plans done, but now I am looking at what to do underneath.

I have an old concrete patio. It is cracked and not in very good condition. Is it best to remove the patio? or can I secure my footings to it?

If I do remove it, what is the best material to put under the deck? gravel or river rock? or something else?

The deck is 16" high with one step down.

staples
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    I'd argue that this is a better fit for [diy.se] since it's about designing and building a structure (albeit one that's in a garden) that isn't directly providing a habitat for plants. If so, we can migrate it there. What say you, gardeners and landscapers? – Niall C. Oct 08 '15 at 14:29
  • I think its okay here, though further details about exact construction rather than the soil/patio beneath might well cross over with Home Improvement... – Bamboo Oct 08 '15 at 14:47
  • @NiallC. Maybe a discussion is necessary to decide what falls within the remit of a landscaper and what falls into Home Improvement - I'd argue that any decent landscaper knows full well how to construct a deck, or anything else, within a garden. Equally, a general builder can do it - but they never take into account the soil and general conditions for surrounding horticulture. So far as I'm concerned, if its in a garden, its a landscaping specialist, not a general building job (although the latter are cheaper) – Bamboo Oct 09 '15 at 12:42

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If the concrete is all broken and moving around, you can't secure your deck to it. You haven't said whether your deck is going to be raised off the ground quite high (in which case, securing the foundations properly is critical) or as close to the ground as possible, but the other problem with cracked concrete is weed growth coming through, and that will carry on even when your deck's over the top. Its probably best to remove the concrete, but if its a concrete pad, it may be up to 9 inches thick, so depends what's there and how bad it is. If it is very thick and not moving around, its probably safe to put your foundation posts into it, but you'll need fence post type fixings with a flat plate so you can fix through to the concrete. Link here (its a UK one) giving general instructions re deck building, raised or otherwise, giving particular guidance on the foundation for the deck

http://www.diy-extra.co.uk/how-to-install-decking.html

As for what you put beneath it, a thicker geotextile membrane, the sort used under driveways rather than the common, thin 'weed membrane' sold everywhere. Spread it out, with a good overlap for joins of at least 8 inches, staple it down, rocks or gravel or whatever you can get over the top, doesn't need to be a deep layer, just something that will keep the membrane anchored down once the staples wear out, and to make it more attractive if the area beneath the deck is visible from another area of the garden.

Bamboo
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  • The deck will only be raised 14". The bottom of my door is 16" off the ground, so it isn't a very high deck. There will be two levels, one at door level, the other a step down that wraps around the first level. – staples Oct 09 '15 at 12:28
  • Yep, got the picture - if there's more garden below the deck at a lower level, it may still be possible to see beneath the deck - if that's not the case, then any old stone on top of membrane will do, whatever's cheapest, doesn't have to be aesthetically pleasing. Old lumps of concrete will do, doesn't even have to be a complete covering, although if the deck has gaps between the planks, probably best to cover membrane completely. – Bamboo Oct 09 '15 at 12:36