Home builders, do you want to avoid dissatisfied clients with regard to sunken and settled concrete? Here’s how.
Follow industry guidelines for compaction. Yes I know these are not enforced but they are a sure way to nearly eliminate all settling. It costs to do compaction according to industry standards, it costs to take the tests and document the results, however by doing this you insure the end user, the homeowner a superior product. Advertise it, let potential clients know you provide a service that virtually no one else does. Quality sells.
Do not pour concrete on unprepared top soil. All concrete should be poured over at least four inches of compacted gravel. Concrete is porous, water moves through it fairly quickly, if all it has is soil to drain into, and that soil is clay (which is expansive) the slabs will heave with the moisture and crack. Compacted gravel allows water to drain safely away.
Don’t saw cut control joints, form them into the concrete. We have found virtually all control joints which are saw cut, are not of sufficient depth to work as intended. Conversely, we have found formed control joints nearly always perform as intended.
Use rebar. In most cases concrete will crack, whether due to shrinkage, thermal (expansive soils) or dynamic loads. Rebar allows concrete to crack without causing the slab to dislocate vertically or horizontally. A cracked slab with rebar can always be Slabjacked, without rebar it is much trickier to align the slabs perfectly.
Pin horizontal slabs to vertical walls with 5/8″ rebar when possible. Driveways to garage foundations. Patios to foundation walls. Garage floors to foundation walls. Yes it is more work, but when coupled with proper compaction, provides an added element of stability for the slabs.
Provide a foundation or at a minimum, Sonotubes, under all entries which are more than a simple 4″ to 6″slab. Blueprints rarely specify the type of entry, rather this is dictated by slop of the land and personal preference, as a result the architect does not draw a foundation for this section of the house. We recommend all concrete entries have a foundation or at a minimum, Sonotubes of ample size, tied into the entry with rebar to support the weight anticipated.
All step up entries, all entries with columns, or those that act as support for any superstructure need to be extremely stable, in addition to the above we also recommend pinning with 5/8″ rebar every three feet to the foundation wall.
Backfill all slabs which will be in excess of 8″. A small entry of six by seven with two steps, if poured without backfill will weigh in excess of five tons and requires over three cubic yards of concrete. Poorly compacted fill simply cannot support this load and will settle until sufficient bearing loads are reached. This may be one inch, it may be a foot.
Don’t make the addition of gutters and down spouts an option, install them on every house you build. Plan for the elimination of water away from foundations walls at least five feet and slope soils well away from foundations, this will not only keep any basements dry but will greatly reduce settling concrete slabs.
Finally, if you are dealing with settling concrete on a job, call the concrete raising professionals 1-855-752-2522 – 1-855-752-2522
Superior technology, superior polymers, superior training, produces superior results.
December 19, 2017 at 3:33 pm
I appreciate what you had to say here about concrete contractors and how to build more effectively. The one thing that you said that I connected with the most was about how you should never pour concrete on the unprepared topsoil. It has always been my dream to become an engineer and work on building things, so this information is really interesting to me. Thanks again for the post, and It is interesting to me that you should always pour concrete at least four inches over compacted gravel–I will remember!