Driveway Assessment Standards
A given residential driveway will be assessed based on three factors – Cracks, Displacement, and Spalling or Surface Degradation.
1) A driveway should not have an excessive number of cracks.
a. Within a given 10′ x 10′ area (based on a chalk line drawn in a “worst case” part of the driveway, the visible cracks shall be counted. Each continuous crack line greater than 6″ long will count as a crack.
b. Based on the number of cracks identified, the driveway will be evaluated as follows:
i. 0-4 cracks – acceptable driveway.
ii. 5 to 7 cracks – consider replacing within 12 months.
iii. 8 or more cracks – replacement required within 30 days.
c. A driveway displaying excessive cracking should be replaced, entirely or within the cracked joint pattern section. Replacement concrete should match the original.
2) Displacement – A driveway should not have any cracks or joints that show a significant vertical or horizontal displacement.
a. Within a given driveway segment, no crack should show a vertical or horizontal displacement of greater than 1 inch. (The crack cannot be more than 1 inch wide or show an up – down difference of more than an inch.)
i. A single crack with1/2″ or less displacement is acceptable.
ii. A single crack with between ls and 1 inch displacement should be addressed within 12 months.
iii. A single crack or joint showing displacement of 1 inch or greater shall be replaced or repaired within 30 days.
b. It is acceptable to “mud-jack” a driveway or sidewalk surface to repair a displacement problem, however, replacement of the entire impacted joint section(s) is recommended.
3) Spalling or Surface Degradation – from time to time the surface of a concrete driveway may experience surface spalling or similar degradation due to chloride (salt) intrusion or a flaking of the cement surface that exposes the aggregate within the concrete. Aggregate “pop-outs” are also typical of a concrete surface degradation that results from improper finishing or poor quality aggregates. Any driveway showing excessive surface degradation should be replaced,
a. Assessing surface degradation can be quantified by drawing a 10’x10′ chalk line in a given driveway area. An evaluation of the % of the area impacted can be made. Only surface degradation greater than X” in depth or that exposes theaggregate within the concrete is excessive.
b. The percentage of degradation that is acceptable is as follows:
i. 0 to 20% degradation or exposed aggregate is acceptable.
ii. 20% to 50% degradation should be addressed within 12months.
iii. Greater than 50% degradation as evidenced by exposed aggregate should be replaced within 30 days.
iv. Also, if 80% or more of a given driveway shows visible degradation (flaking or powdering of the surface) or extensive discoloration without evidence of exposed aggregate, or if a driveway is stained in excess by oil or more of its surface area, or other similar nonconforming driveway surfaces surfaces as 80% evaluated by the ACC as not keeping in harmony ofthe neighborhood, replacement or repairs should be considered
c. Patching – while patching and filling is an acceptable approach to repairing a driveway with cracking or surface degradation, it typically is not a long term fix. A driveway showing excessive patching with a range of patchwork colors across the surface, may be functional, but is generally not in keeping with the design guidelines of the neighborhood and should be considered for replacement.
4) Replacement driveway guidelines (use only insured contractors with a good track record.)
a. A replacement driveway should be equal to or better than your existing concrete driveway. As a guideline, the following concrete specifications should be considered,
i. Use a 3000 PSI or greater concrete mix (high strength.)
ii. The concrete should be at least 4/1 thick (6/1 is better.)
iii. The concrete should be placed on a layer of compacted aggregate (such as #6 road base)
iv. Use reinforcing bar (#6 bar tied at 24″ centers or better) or heavy gauge welded wire mesh to hold the joints together. Reinforcing is kept within the concrete and not at the bottom of the pour.
v. The concrete must be finished to a smooth uniform surface, with no exposed aggregate, within an hour of placement. A stiff broom swept surface is a good idea to provide traction and a secure walking surface in the rain and snow. Use of a curing get sprayed uniformly across the surface is also a good idea to ensure a solid surface degration and spalling.
vi. Use of stamped or colored concrete or other decorative surfaces should be approved by the ACC in advance.surfaces should be approved by the ACC in advance.
THOA does not recommend or take responsibility for any contractors or any specific concrete or aggregate materials companies. Please use common sense and research any concrete driveway or sidewalk contractors that you may select to prevent inferior quality work. Cracks in the street, curb, gutter, or the sidewalk in front of your home are the responsibility of the City of Centennial and not evaluated by the THOA or ACC. The City has a phone number on their web site to address any concerns within the Public Right-of-Way.
Tom Wood 9/5/12