Site preparation includes several steps. A survey comes first. Topographical features — trees, streams, rocky outcroppings, relative elevations, and open areas — are carefully marked, providing the basis for everything that follows. Property lines must be located precisely to confirm setbacks (the allowable distance between a structure and a property line) in compliance with local codes. Streets and sidewalks are mapped and flagged. Then the surveyors stake out the location of the various underground utility conduits through the neighborhood and to each house. In the case of a single house under construction, the existing utility services in the neighborhood must be located and the connections to the proposed house carefully plotted. Finally, a soils test is ordered to help determine the type and design of the foundation construction.

Most, if not all, of this information is mandated by the local building authority. Copies of the surveys and tests, usually signed and stamped by a registered professional engineer, must be attached to the proposed construction drawings and submitted for permits or approvals from that authority.

Once those steps are taken and the plans are approved by the building department, the next “site prep” step can be taken. The location of the foundation or footprint of the home is staked to provide a guide for excavation. Typically, the stakes and batter boards (which demarcate every corner or turn in the layout) are connected by nylon strings to outline the exact perimeter of the foundation to be built.

Then backhoes or excavators can get to work, digging ditches to extend existing or new utility conduits — for electrical, plumbing, natural gas, etc. — to serve the house (or houses). Foundations are excavated using the staked-out lines as a guide. The plans will call for footings and — according to individual designs — a crawl space, full basement, concrete slab, and/or perimeter foundation walls in preparation for concrete forms, blocks, or other materials to support the main floor.

Every new-home project requires these site prep steps, and it is important for our homebuyer clients to understand this phase of the job to track our progress and get a complete picture of what is required to build their new home.

Warm

Pervious concrete allows water to flow through thereby slowing down the water run-off rate.

Pervious concrete can take in storm water at a rate of 3 to 5 gallons per minute per square foot of surface area. That exceeds the flow rate needed to prevent runoff in most rain events. The rainwater may be stored in a coarse gravel layer underneath the pavement or allowed to percolate into the underlying soil. Because the pavement itself acts as a retention area, it helps to prevent much of the polluted runoff that normally occurs with impervious pavements.

Can it get stopped up? It’s unlikely that a pervious surface will become totally clogged. Reducing erosion and sediment runoff onto the pavement through good design can eliminate most problems. If any voids do become clogged, vacuuming or pressure washing of the pavement can restore most of the permeability.

What are the limitations? While this thirsty pavement is an excellent option for certain situations, it may not always be a viable choice. Because pervious concrete has a rough-textured, honeycombed surface, moderate amounts of surface raveling are normal. This can be a problem on heavily traveled roadways.

Special attention must also be given to the overall design of the pavement system in order for pervious concrete to perform as intended. Proper engineering of the substrate beneath the pavement is essential, since it must be able to temporarily store the water while it percolates into the soil. An initial soils site survey and site-specific stormwater calculations should be performed by a stormwater management engineer.

Installation: Pervious concrete is delivered to the jobsite by conventional ready-mix trucks and placed within

A heavy roller press is used to place pervious concrete.

standard forms. Because pervious concrete is thicker in consistency than regular concrete, a vibrating mechanical screed is used to level it off. Vibration is followed by compaction with a heavy steel roller to attain greater strength.

Because pervious concrete has a low water content, curing is especially critical. After placement, the concrete is misted with water and then covered with plastic sheeting and kept damp for at least 7 days to allow full hydration of the cement.

Often paving crews can complete pervious concrete jobs faster than when installing regular concrete. That’s because pervious concrete doesn’t need to be worked with a bull float or trowel, since these finishing operations can seal off the pavement surface and decrease water penetration.

More:

Ten Strategies for Ensuring a Successful Pervious Concrete Installation

Pervious concrete design ideas

Sources:

www.concretenetwork.com

http://porterworks.com/