Most Common Construction Errors

The inspectors were asked to summarize the most frequently found code-related mistakes made during construction or installation. This is their response.

Common Error Categories:
Plumbing | Structural/Building | Electrical | Mechanical

PLUMBING:	Water Heaters: Loose electrical connections Flexible gas connections used Flexible water connections used Drainage & Vent Piping: 90 degree bends on horizontal runs instead of 45 degrees Undersized vent lines Horizontal vent piping run longer than code allows Lack of water or air pressure testing of pipes Trim: Dishwasher not anchored to counter Dishwasher drain not looped and anchored to top of counter Dishwasher drain connected to garbage disposal
STRUCTURAL / BUILDING:	Foundation: Footing not the proper width or depth Soil does not meet minimum bearing capacity (black humus soil) Footing does not have 2'x4' keyway Missing reinforcing steel Steel reinforcing not lapped at ends and corners Steel reinforcing too close to forms (do not have 2' concrete cover) Floors: Framing varies from approved job site copy Improper joist hanger and/or improper fastening of joist hangers Improper boring and/or notching of joists Trimmer joist at openings not doubled Improper fastening of floor sheathing Damage to prefabricated floor trusses Walls: Improper boring and/or notching of wall studs and plates Fireblocking at chase, soffit and tub waste pipe Improper fastening of exterior wall sheathing Improper fastening of wall studs Improper transfer of concentrated loads under headers and beams (cripples) Firestopping of top and bottom plate penetrations not installed Improper fastening of foundation anchor bolts to bottom plate Roofs: Improper boring and/or notching of rafters Damaged pre-fabricated trusses Sheathing not fastened properly Asphalt shingle fastening not to manufacturer requirements Stairs: Improper height of guardrail and/or baluster opening Handrail missing or improper height or gripping size Improper clearance to handrail from adjacent wall Handrail not continuous Improper riser depth Improper tread width Improper tread dimension on winder stair Handrail not continuous on winder stairs Headroom not 6'x8" Insulation & Ventilation: Vapor retardant missing or reversed R-30 vaulted rafters (no blow-in) Baffles missing Insulation not secured Exposed paper backing on insulation in basement Insulation missing at rim joist Exterior side of walls or roof not sealed against the weather Eave vents not installed Ventilation blocked by insulation
ELECTRICAL	Underground Conduit Depth: EMT (thinwall) buried in the ground Heavy wall not buried the required 6' below grade PVC conduit not installed 18' below grade Direct burial cable not installed 24' below grade Underfloor: Conduit not strapped Connectors and couplings not tightened Rough Walls: Boxes not fastened securely Conduit not strapped 3' from any boxes Rough Ceiling: Boxes not fastened IC type recessed fixture must be used if ceiling is insulated Closet fixture light boxes not 18' minimum from the back wall of the closet Electrical Service: Service wire not clearing the roof by 18' Service mast shall be secured with proper type screws or bolts (not drywall screws) Service wires not 10' above grade End of conduit for the ground conductor going to the ground rod not grounded Bond bushing not installed on concentric knockout Bond jumper on the neutral bar not installed Jumper wire at the water meter and proper ground tag not installed Ground rod at electric meter not driven 8' and below grade Final inspection: All electrical equipment not complete, hooked-up and working Every fixture must have working bulbs All devices shall be turned on for testing Island or peninsular counter outlets shall be mounted not more than 6' below the counter top and shall not be mounted where the countertop extends more than 6' beyond its support base Motor for the jetting tub not grounded with a #8 AWG wire back to the conduit system Breaker for A/C compressor is larger than manufacturer's label indicates for maximum overcurrent protection Wire Inspection (required): Box fill is exceeded (check Table 370-16 of National Electrical Code) Outlets and switches not grounded to the junction box with a green wire, if the device is not self-grounding type
MECHANICAL	Duct Installation: Ductwork not fastened together at joints Sealing tape not applied on joints Ductwork not installed to plan Bath fan not vented to the exterior Kitchen hood vent not installed properly Dryer vent ductwork over 25 ft. in length and reduced 5 feet for each 90 degree bend Ductwork in crawl space not suspended at least 4 inches above earth Ductwork in crawl space suspended more than 6' below the floor Duct openings not protected (covered) during construction Duct work in unconditioned space not insulated Furnace Installation: Furnace installed without proper clearances Insufficient clearance between closet door and furnace Clearance between B-vent and combustibles is less than 1 inch. Clearance between single wall flue pipe and combustibles is less than 6 inches. Single wall flue pipe cannot be run through ceilings or floors Drain liens for furnace not installed A/C unit coil not installed B-Vent installed with more than 2 - 90 degree elbows Furnaces Installed in Attic: Incorrect working clearances (must be 22' wide and 30' high) Work area in front of furnace must be 30' long and 30' high Must have outlet and light in furnace area Light must be switched at opening to attic Attic access must allow removal of furnace's largest part Drain pan under A/C coils with two (2) drain lines, one (1) to conspicuous place