Guides

How-to guides for contractors

Straight answers to the math you do every week - with the worked examples - from the team behind Sentinel Nexus.

• Fire Alarm

  NFPA 72 Smoke Detector Spacing: The 30-Foot Rule Explained

  How far apart smoke detectors go under NFPA 72: the 30 ft nominal spacing, the 0.7 x S (21 ft) rule, wall distances, corridors and a worked layout.

  7 min read

• Fire Alarm

  How to Calculate Voltage Drop on a Fire Alarm NAC Circuit

  Step-by-step NAC voltage drop: wire resistance per 1,000 ft, the 20.4 V starting voltage, the 16 V end-of-line check, and a worked horn-strobe circuit.

  6 min read

• Exterior & Siding

  How to Price Siding Per Square (With a Worked Example)

  Measure walls and gables, subtract openings, add waste, convert to squares and price materials, trim and labor - with a full ranch-house example.

  6 min read

• Painting

  How Much Paint Do I Need? A Painter's Estimating Method

  Figure wall and ceiling area, subtract doors and windows, apply coverage per gallon and coats, and estimate paint for a whole room - with an example.

  5 min read

• Estimating

  Good / Better / Best Estimates: Win Bigger Jobs Without Haggling

  Why offering three options closes more jobs at higher prices, how to build each tier, and how to present it so the customer chooses instead of shopping around.

  5 min read