Design & Construction Strategies

The following specific design and construction strategies will result in the lowest first cost:

Site Planning

  • Attempt to balance cuts and fills as best as possible with a preference for excess fill rather than a need for import. Look for opportunities to use existing grades where possible.
  • Limit the use of curbs to allow surface runoff of parking areas (reducing storm piping) and easing removal of snow in winter in northern climates.
  • Use surface drainage like swales or rain gardens as much as possible to reduce sediment runoff and keep storm water piping costs down.
  • Use surface parking in lieu of below grade parking whenever possible.

Unit Design

  • Projects that minimize the variations in units are most competitive. To the extent that bathroom layouts or bedroom to bathroom corridors are consistent - this lowers costs even if the units themselves have different layouts.
  • Use galley kitchens. They are efficient for cooking plus they eliminate the need for lazy susans or blind corners and make countertop installation quick and simple.
  • Locate HVAC closets outboard of the unit to reduce ductwork runs.
  • Keep washer/dryer closets within 25’ of an exterior wall to reduce need for in line booster fans.
  • Keep bathrooms off outside walls and place them back to back where possible. This reduces freezing potential in northern climates and reduces piping through combined services and proximity to hallway circulation loops.

Structure and Building Envelope

  • Shallow foundations with slab on grade where possible (avoid crawl spaces or basements). Use thickened footing for interior bearing walls.
  • If below grade parking is required, use precast columns, beams, and plank with poured concrete walls. This system can provide a cost effective transfer slab that works with above grade framing system listed below.
  • Use water proofing and underdrains on foundation walls only at occupied spaces below grade.
  • If project is located in a state that has adopted the 2012 energy code, use continuous 1” rigid insulation on the building exterior. Hardie siding and vinyl can be nailed through 1”, 2” or greater requires strapping or Z channel.
  • Wood frame will offer the lowest first cost structural system for all buildings 5 stories or less.
    • All dimensional lumber SPF #2 or equal in structural properties (if greater strength is required at ground floor Doug Fir is next most cost effective).
    • Frame floors parallel to corridors spanning from unit to unit and living room/bedroom separation walls. This keeps span length and floor truss sizes to 14” or less. Roof trusses bear from corridor walls to exterior walls. This spreads the load, prevents double studding, and plate crush.
    • 7/16” OSB ext sheathing, 23/32 T&G Advantech floor decks (northern climates, pine T&G southern climates), 19/32 OSB roof sheathing.
    • ¾” gypcrete topping on all above grade floor decks with low profile sound mat only at hard surface floors. Floor ceiling assemblies utilized sound insulation and RC channel.
    • Limit use of structural steel. Use LVL’s or other engineered wood in lieu of steel where possible.
    • Pre-engineered wood stairs in all stairwells in lieu of metal pan with concrete fill.
    • Stairwells and elevator shafts can be masonry if they contribute to help with shear loads. Otherwise wood walls are acceptable.
    • Unit separation walls, 2x4 staggered stud on 2x6 plate with RC channel 1 side and weaved sound insulation - could be sheathed with OSB as needed for shear. If greater STC is requested or required use double 2x4 stud wall with sound insulation and no RC.
  • Attic insulation R-40 stabilized cellulose wherever possible. Avoid batts unless vaulted ceiling where access is difficult.
  • Shingle roofing where possible on walkable pitch. Limit flat roof. Flat roof to be EPDM with rigid insulation just to form crickets for interior drains. Pitch roof trusses for general drainage.
  • Limit brick and cultured stone to accent areas. Use Hardie panel if possible in accent areas to minimize skin costs. Vinyl will be lowest cost if Owner will accept it.
  • Avoid gutters and downspouts (maintenance is a headache). Provide drip strip with underdrain system.
Wood framing remains the most cost-effective structural system for buildings up to five stories

Mechanical

  • 95% AFUE stand alone furnaces with 13 SEER condensers typically offer the best combination of first cost, efficiency, and maintenance. Condensers can be located on the roof in a well if ground location is unacceptable. Locate furnace closets at exterior of unit to reduce ductwork and use central returns and residential grilles.
  • If building must be all electric - ductless mini split or ducted fan coil offer the lowest first cost.
  • Use Supermini splits with DX cooling and mini ERV for hallways. This is essentially a pressurized hallway system.
  • Use ductless exhaust for kitchen hoods as permitted by local code. Duct bath fans and dryers horizontally to the exterior. Keep dryers with 24’ of outside wall if possible to avoid need for booster fans.

Plumbing

  • PVC waste and vent above and below grade.
  • Cast or copper water distribution sizes 3” or greater, CPVC or pex for smaller sizes.
  • Run main water distribution on a continuous circ loop in the hallway of a middle floor. Valve off into a unit stack and feed all units in the stack vertically from there.
  • Use one piece cultured marble tops for bath sinks.
  • Use one piece fiberglass tub/shower surrounds with a hand held shower wand.
  • Toilets are comfort height floor mounted flush tank style.

Fire Protection

  • Utilize NFPA 13R system in all residential areas. NFPA 13 in commercial areas.
  • Avoid standpipes unless required by code. Should not be needed except in 4 story applications.
  • Use of CPVC piping as allowed by NFPA.
  • Semi recessed heads in white or chrome in ceilings or walls, brass upright heads in exposed pipe locations.
  • Mains sprinkler distribution in first floor corridor. Branch piping run off main into units and feed vertically with sidewall heads to other units. Avoid any piping in unconditioned attic spaces.

Electrical

  • Use NEC optional calculation method with load shedding to minimize gear size.
  • Use aluminum feeders for all secondary and distribution to sub panels.
  • Use SER cable from the main gear to individual apartment load centers.
  • Branch wiring uses 12-gauge Romex for general circuitry and 14-gauge for lighting as permitted by code.
  • Use residential devices and plastic back boxes. No Decora switches.
  • Outlet spacing per NEC minimums.
  • One USB outlet per unit located in kitchens.
  • GFCI circuits can be protected downline in lieu of GFCI's at all locations.
  • All open plenum wiring. No conduit and wire unless in exposed areas.

Finishes

  • Using 5/8-inch Type X drywall throughout provides a stiffer wall for just pennies more, while eliminating any potential inspection issues caused by mixing drywall types on fire-rated walls.
  • Prefinished MDF colonial casing and base.
  • Pre-primed Masonite hollow core pre-hung doors at all interior unit locations with Schlage F series hardware.
  • Provide 20-minute fire-rated, insulated metal-skin doors in "Adjust-A-Fit" split-jamb framesat all unit entrance with spring hinges.
  • Paint Spec: 2-coat system (1 prime, 1 finish).
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