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Final Grade & Exterior Concrete

Roofing | >>Final grade | Soffit and fascia | Electrical and gas laterals | House wrap | Masonry | Stucco | Siding | Exterior concrete | Exterior paint | Foundation parging

Intro
Final grading and concrete preparation usually takes place at the first part of the exterior (phase 4) phase. Typically the grading is done with a combination of the following: Backhoe, skidsteer (aka-Bobcat™), front loader or track hoe. Suitable base material (Gravel, road base etc.) needs to be brought in where walkways, driveways and concrete slabs are planned.

Grade
According to the Code the soil must slope away from the foundation @ 5% for 10'. Another important factor is that water runoff must run from your property to the street or public property. Driveways and walkways need to have a slight slope to drain water. Some cities require a grading plan as part of the permit application. This is required to ensure that your water runoff doesn't end up flooding your neighbors property. It may be necessary to consult an engineer/landscape architect to design a drain plan for your project.

Concrete Preparation
It is important to know the elevation at which the concrete will be placed. In most situations it will be obvious. For example, the driveway will need to be flush with the sidewalk edge. A transit or laser level may be used to determine the elevation of patios or slabs. Once the elevation of a slab is determined, the soil must be excavated down the thickness of the slab plus any fill. Remember it is a good idea to slope the slab away from the house slightly (2-3%) to alleviate standing water.

Landscaping Plan
If part of your construction documents includes a landscaping plan now is a good time to get the excavation contractor and the landscaping team together. Excess dirt from the excavation can be used for landscaping. Time and effort can be saved if the excavator and the landscaper work out a grading plan that works for the Grade and the landscape plans. Even if you don't have a landscaping plan, it is a good idea to bring in topsoil (4-6"deep, if conditions warrant) at this stage. You will then be ready to plant as soon as the construction is complete.

Gravel Base
The Description of Materials document should specify the type, compaction requirements, and depth of gravel required under exterior slabs. In poor compactable soils (clay, silt and sand) compacted road base is used to give the slab extra strength. Where soil strength is not a concern, pea gravel is often used because it give does not require compaction. The gravel is place to a depth of 4-6" inches in most circumstances. Ask your concrete contractor what he recommends for your particular area.

Irrigation & exterior lights
Whether you have plans now for an exterior irrigation system or exterior lights it is a good idea to plan for them. If you have a landscaping plan the landscapers will need to place any sprinkler pipe and electrical wires underneath exterior concrete slabs where they cross before concrete is placed. If you don't have detailed plans at this point (most people don't) Place plastic pipe underneath under the walkways and driveways at strategic points. This will allow you to feed pipes and wires underneath the concrete without having dig below or cut the concrete away from above. Use 2-3" plastic pipe to accommodate sprinklers pipes and 1-2" pipe for exterior wire.

Notes to the Owner-builder
The final grade and concrete preparation can be done during this phase or at the end of the project. Since there is sufficient time now it is a good idea complete it as soon as possible. If the weather will improve as you get closer to the end of the project you might decide to wait, as grading is difficult when the ground is frozen.
It is important that the final grade is done by experienced excavators especially if you schedule the final grade at the end of the project. It's not to uncommon (in our experience) for inexperienced operators to damage siding, brick or stucco while completing the final grade.

 

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