Project Delivery System
Design/build is the preferred project delivery system for the concrete skatepark construction. The Design Build Institute of America defines design/build as "A system of contracting under which one entity performs both architecture/engineering and construction under one single contract."

Our particular brand of design/build is slightly more rigorous; all Airspeed designers play an intimate, hands-on role in the skatepark construction process, especially form work, concrete placement, and finishing. It is absolutely crucial that design/builders have the freedom to alter the design as they see fit within contractual limits. Excellent design/build contracts are available from DBIA.

Skatepark Construction

Skatepark Construction & Design
Skatepark designers must be active skateboarders, able to understand and appreciate their own work and the work of their peers. As stated above, skate park design/builders require the freedom to alter their design at any time during the skatepark construction process.

Dirt Work
All substrate beneath non-structural slabs should be compacted to at least 90% of maximum density as determined by standard proctor at optimum moisture content. The final layer of substrate should consist of compacted granular material such as sand or gravel whose thickness complies with local code. In regions subject to freezing, a local engineer must be consulted, as a thicker gravel layer and rigid polystyrene foam insulation may be required to prevent frost heave.

It is often necessary to build upwards to avoid excavating below the water table. In this case, it is common practice to pour the transitions against removable forms. The forms are typically removed after several days of curing and the transitions are backfilled as if they were retaining walls. This practice is entirely appropriate as long as the backfill is compacted in 1' lifts to 90% of maximum density.

Drainage
Especially in rainy climates, skateparks need to dry quickly. Puddles are to be avoided. To that end, decks and flats should slope at least 2% (1/4" per foot) towards the nearest area drain or outside edge where water can exit the skatepark. Drain covers should be flush with the riding surface and firmly attached, but removable for cleaning.

Wherever near-surface ground water is present, a local soils engineer should be consulted and perforated pipe under-drains should encircle the park. If an infiltrator system is used, it should include a 3' minimum diameter access shaft for sediment settling, retrieval of lost objects, cleanout, and pumping.

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Formwork
Forms and templates used to define shapes of transitions and other structures should be firmly supported and adequate to ensure that the finished structure can conform to design specifications. Design/builders often make crucial design adjustments in mid pour, so slavish dependency on form work is undesirable.

Skatepark Construction: Rebar
For non-structural skatepark construction slabs, #3 grade 60 rebar placed on one foot centers and tied every other junction is sufficient. Rewire can also be used. Rebar should be covered by at least 2 inches of concrete, above and below. For retaining walls and self-supporting structures like full-pipes, see local codes and consult a structural engineer.

Steel Coping
Coping diameter may vary considerably, however 2" to 3" OD is commonly used and very acceptable. Tiny or huge coping can also be used in moderation for novelty.

Typical coping reveal at lip of transitions is ¼" to 3/8" (applies to both top and face). As is the case with coping diameter, larger or smaller reveals can be functional in appropriate applications. Galvanized and black-coated steel schedule 40 sprinkler pipe are commonly used for coping. Stainless steel is neither necessary nor desirable. Steel coping must be securely anchored into the concrete. To accomplish this, coping may be either welded to the rebar cage at least every two feet or welded to mud lugs placed every two feet. For ledges where an angled edge is desired, square tubing is superior to angle iron.

Concrete Coping
Penrose blocks are favored above all other pre-fabricated coping blocks for their durability and grinding characteristics. Poured-in-place concrete coping also yields excellent results when poured by an experienced skatepark construction crew.

Skatepark Construction in Florence, Oregon

Shot Crete
Mix designs vary from region to region , depending on locally available materials and local conditions. Typical shot Crete specs are 3000 psi minimum strength, 7-8 sacks of cement per cubic yard. Plasticity varies with application and mix design, but shotcrete should not be wetter than a six inch slump. Fly ash, silica fume and steel slag are also common components of shotcrete mix designs.

During shotcreting, measures must be taken to prevent the formation of voids and rock pockets. To this end, accumulations of loose rebound aggregate must be removed, either manually or with the aid of compressed air.

Ideally, the shotcrete finish layer and the layer which encases the rebar should be shot on the same day. If several days pass between successive layers, concrete bonding agent should be applied to the old layer before shooting the finish layer.

Shotcrete overspray on existing slabs should be cleaned off immediately, if possible.

Conventional concrete
For flat slabs, decks, and small transitions, 4000 psi concrete is often specified in order to ensure a creamy mix that can easily be floated and trowelled smooth. However, the psi strength is of secondary concern-what really matters is finish smoothness and resistance to wear and weathering. The mix designer at the local batch plant should always be consulted, as materials availability and severity of weathering varies with region. Aggregate size typically ranges from ½" minus to ¾" minus, with the smaller aggregate being easier to finish and the larger being cheaper.

Concrete Placement/Shaping
Shapers and finishers should have adequate floats, trowels, screeds and other tools sufficient to ensure that all curves/transitions will be continuous without perceptible bumps or kinks, unless kink is specified by Designer. Specialized skatepark construction teams have custom-made tools which are not familiar to conventional concrete contractors. In addition, the skills needed to shape, float and finish steep transitions without introducing hideous lumps are specific to skatepark specialists. These are two good reasons to hire a design/build team.

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Concrete surface finish
Steel trowel finish on all riding surfaces is mandatory. The last pass before blackness is sufficient. Broom finish is only appropriate for pedestrian walkways around a skatepark. Over-vertical surfaces like the ceilings of full pipes need not be trowelled if they are formed using a smooth material like masonite.

Skatepark Construction: Curing
After the last toweling, concrete should be sealed with a dehydration retarding compound such as acrylic cure and seal or penetrating silica-based sealer, also known as "liquid glass". In addition, new pours should be tarped for at least a week after pouring if dry weather may occur. If freezing temperatures occur, fresh slabs must be insulated and tarped. Ideally, skateparks should not be poured in freezing conditions.

Slab Joints
In order to ensure a smooth, fast and quiet ride, all joints between slabs should be smooth and flush. No sidewalk type joints with expansion board are desirable. Saw cuts should be filled with an appropriate caulking if width is larger than 1/8" in width. Butt joints must be spanned by rebar.

Toledo, Oregon Skatepark Construction

Edging
Edging with a radius edging tool should be performed along the outside edges of slabs and on either side of coping. Butt joints need not be edged, but if edging is performed it is necessary to utilize a custom-made edging tool with an extremely tight radius.

Safety Railings
Safety railings should be placed in accordance with applicable OSHA or ADA requirements. Railings need not be placed at the lip of any transitions, but are necessary at the tops of full pipes.

Skatepark Construction: Cracks
Shrinkage cracks and surface crazing are cosmetic blemishes which do not affect the riding characteristics of a skatepark. Shrinkage cracks can be minimized by the use of dry mix, high cement content, and fanatical prevention of dehydration during curing. Surface crazing is a characteristic of very smooth steel trowel finishes, and can be minimized during floating and finishing by limiting the use of water. Proper curing also minimizes crazing.

Settling cracks are more serious because they create perceptible discontinuities in the riding surface. Fortunately, settling is avoidable by adequately compacting the substrate and preventing frost heave where appropriate.

Find more Skatepark Consruction Examples in our Photo Gallery

 

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