Concrete driveways on Dug Gap and Tibbs Road

What is different about a Dug Gap job?

The ground, and how much of it has to move first.

The corridor runs from cul-de-sac subdivisions and townhomes near the commercial strip at the bottom, up to Tibbs Road where lots average around half an acre, and on into large lot and acreage tracts climbing Dug Gap Mountain. The higher lots have elevated views, which is the reason people buy them and the reason concrete costs more there.

On a flat lot near downtown, site preparation is close to nothing. Here the pad is made rather than found. Cut into the slope, fill and compact the low side, check the fall, and only then form anything. That is machine time, and it is priced separately from the concrete because it varies so much between two lots on the same road.

Ask for the site preparation as its own line. Against a base rate of $8 to $16 a square foot for the concrete itself, earthwork on a steep lot can add a third to the total, and it is the part of a mountain quote that differs most between contractors.

How steep is too steep?

Steepness is rarely the limit. Drainage and grip are.

A driveway can be built on a considerable grade. What a grade does is concentrate problems. Water runs faster and further, so it needs somewhere deliberate to go rather than the garage door. A vehicle needs traction on a wet surface, so the finish matters more than it does on the flat.

A broom finish across the direction of travel gives grip. A smooth power float, which looks excellent on an interior floor, is the wrong choice on a sloped exterior drive in a climate that ices.

At the top of a steep drive, where it meets a garage or a level parking area, the transition needs care. A sharp change of angle catches a low front bumper, and it is also where water collects if the fall has not been thought through.

What does drainage need on a hillside?

An answer written into the design rather than added later.

A driveway is an impervious surface, and Section 2 of the ordinance defines it that way alongside buildings, roads, parking lots, decks and patios. Whatever soaked into that footprint before now runs off it, and on a slope it arrives somewhere with speed.

The three tools are a channel drain across the bottom of the run, a crown down the middle that sheds to both sides, and a cross fall that carries water to one edge. Which one fits depends on where the water can be released, and that is a site question rather than a catalogue choice.

Getting it wrong cannot be sealed away. Water standing or running across a slab through sixty to eighty freeze thaw cycles a year scales the surface, and a slab that channels water toward a foundation is a bigger problem than a concrete one.

Does the base change on a slope?

The specification does not. The care does.

Four to six inches of compacted graded aggregate is still the figure. The difference is that fill on a slope has to be placed and compacted in layers, because a thick lift of fill on a hillside settles unevenly and a rigid slab over uneven settlement cracks.

Whitfield County ground is red clay with pockets of chert and weathered shale. Clay holds water, swells as it takes it on and shrinks as it dries out, and on a slope it also creeps. Compacted aggregate between the clay and the concrete is what keeps that away from the slab.

Permits for a Dalton address go through Whitfield County Building Inspection on 706-275-7474, not the city.