Sufficient footing?

[Stonehenge]

We have a potential client that would like a privacy wall/planter box enclosing the parger part of their concrete slab patio.

Can I use the patio slab as the footing, and just start mudding up bricks on top of that? The slab is 4"+ thick, with rebar.

[BJR]

Depends on the weight of the wall.

If it is over 4 ft tall I would consult an engineer.

If the wall is too heavy you could crack the slab.

It also depends on what the slab is sitting on. I fit is soft fill, definately not. Can you also trust that the slab is 4in thick with reinforcing.

To be safe I would construct a new footing to your local construction standards for the size wall you want to build. Or consult an engineer.

Where I live I have to guarantee my work for 7 years. If in the 7 years a structural fault occurs, I have to fix it at my cost. Therefore I am overly carefull.

[agla]

Even if you were building these at the same time, it is a bad idea to have a patio slab also act as a wall footing. You should have an expansion joint between them.

[Stonehenge]

I should clarify - it's not a retaining wall. It's just a raised planter box. Approx 2.5-3' in height, possibly 18-24" across, with a large portion of the middle open for plantings.

As for the slab, I know who did it, and yeah, they always do at least 4" thick with rebar.

The 7 year warranty - is that required by law, or just something you offer to do better than your competition? Around here a 1 year warranty is standard (not law), so we offer double what the competition does. 2.

[Stonehenge]

The longest section of wall will be approx 15'. Should we go below the frost line, or just the bell shaped footing like Tim from Accuscreed suggested in another thread?

[agla]

When I was in school they told us a footing should be below the frost line, but I have yet to see someone do that for a normal masonry landscape wall. The professors were living in university land with little practical experience as is usually the case. (student, to grad school student teacher, to associate professor that hooks up with other professors to do civic projects for recognition, to professor- pretty standard resumes in Landscape Architecture acedemia "professorland")

The company that I recently left from, did their walls on 6" steel reinforced footings formed on the face side for the masons to use as a layout line. The back was usually just earth formed. We often poured a slab for bluestone at the same time, but there was always separation even if the form board was left to rot. The slab was 4" steel reinforced. That company is known for very high quality.

PS. Our winters are much milder than yours.

[Stonehenge]

Ok - thanks for the quality info. :D Hey - you're USDA Zone shows 1 - is this not the case?

[BJR]

The 7 year warranty is law.

Also, to do domestic projects over $12,000 we have to supply Home Warranty Insurance. This insurance covers the job for the 7 years. if there is a problem with the job in the 7 years and you don't fix it the client claims on the insurance. the insurance company pays to fix the job then takes the contractor to court to claim all costs incurred. It is basically a gun at your head to insure that you do a dam good job.

To get the insurance the contractor has to sign a guarantee of indemnity to state that if there is a claim, the insurance company can take anything to cover costs. Even your home.

This is why I am so busy. Not many Landscapers in my area are willing to sign their home away.

2 years ago my average job was app $8,000. Some of my next projects are $61,500, $53,000, $80,000, and $85,000. All domestic with some smaller jobs to fill in between.

[Stonehenge]

Very nice. :D I can see why you'd would want to strictly follow guidelines for hardscapes put forth by the gov't there. No incentive to go out on a limb and try something different, unless you like sleeping in a cardboard box. :bag: