Wife and I purchased a house in Plano with a recently installed irrigation system, but no foundation drip lines (only sprays at sides and back of house). We recently had some grading improvements completed, and in the process, determined that supplemental watering is necessary as the soil was very dry below the first couple of inches. The house was built in the 70's and has a history of moderate foundation movement (foundation repair was completed prior to purchase) so I want to add foundation drip lines to supplement the existing irrigation. The drip lines will be placed 12-18" from the slab and will be run off of the exterior faucets (with a pressure reducer and backflow reducer at each connection, along with a timer). I am planning to use Rain Bird 1/2" emitter tubing with emitters spaced at either 12" or 18". Considering the clay soils in the area, would 12" or 18" spacing be more ideal for this use case? Secondly, would it be more ideal to leave the line at the surface (so that it can be more easily monitored), or bury it? Currently, the soil in the areas in question is bare as existing sod was removed during the grading work. I plan to come back with some form of cover at a later point.

I.
The best results in Aggieland illite expansive clay soils have been pro-installed WITH moisure sensors that control the drip ports SO that an even, consistant moisture content on all sides perimeter is achieved.

This goal has been almost impossible for busy homeowners, complicated by weather and dicey hand monitors.

We are ONLY talking about slab-on-grade reif.conc foundations, NOT slab-on-piers or similar.

The above systems are best buried below frost penetration and in deep mulch that is renewed annually, even though it's best to drain before freezes. Doing a perk test, even if only DIY will reveal the spacing of the ports, be they 12-18-24 or even continuous if can be any silt prevention.

II.
The other solution is to attack the foundaiton corner that is drooping due to shrinking supporting clay soils beneath. SOP seems to be the West one or near by due to Texas setting sun dryout. Here one could dig 10ft long trenches from that corner down almost to footing, fill w/gravel, sand, peat moss, then mulch. Fill with water, route any gutter downspouts to this location, employ soaker hose as a last resort ... .then wait 6-18 months for uplift corrections.

III.
Those with money and no patience for DIY hire the most experienced Anchor Foundation in Aggieland that jack it up, install slat conc. piers, belled, then adjust any problems free for ... 2 years? They have a website that "'splanins it to us, Lucy".