| Robert's Electric | Robert A Forslund | — | (530) 926 2712 | Electricians | Mt Shasta · Siskiyou County | — | — |
| Roberts Energy Services | Bradley Keith Roberts | — | (530) 574 4529 | Electricians | Weed · Siskiyou County | — | — |
| Roger Gifford | Roger Gifford | — | (530) 340 1395 | HVAC | Hornbrook · Siskiyou County | — | — |
| Roll'n Rock Construction INC | Bonnie Joy Heile | — | (530) 925 1408 | Tree | Mt Shasta · Siskiyou County | — | — |
| Ron Bear Construction | Ronald Wade Bear | — | (530) 340 5810 | GC, remodel, ADU | Hornbrook · Siskiyou County | — | — |
| Ron Cooper | Ron Cooper | help@smugmug.com | (530) 925 3793 | Other | Mt Shasta · Siskiyou County | — | — |
| Ronald G Morris | Ronald G Morris | — | (530) 925 6225 | GC, remodel, ADU | Mt Shasta · Siskiyou County | — | — |
| Rope Runners Tree Service | Jesse Eugene Womack | — | (530) 859 0327 | Tree | Mount Shasta · Siskiyou County | — | — |
| S D Construction Co | Stephen Frederick Darger | — | (530) 925 2997 | GC, remodel, ADU | Weed · Siskiyou County | — | — |
| S K Custom Cabinets | S K Custom Cabinets | — | (530) 722 7594 | Other | Mt Shasta · Siskiyou County | — | — |
| S V M Plumbing | Theodore Jay Johnson | — | (530) 842 7862 | HVAC | Yreka · Siskiyou County | — | — |
| S W Maintenance Corp | Mark Allen Keys | — | (530) 938 2969 | HVAC | Weed · Siskiyou County | — | — |
| Safety Home Inspectors Inc. | Safety Home Inspectors Inc. | — | (909) 725-1230 | Inspectors | Yucaipa · Siskiyou County | — | — |
| Safeway Painting | Safeway Painting | — | (530) 643 2872 | Windows, patio, painters | Montague · Siskiyou County | — | — |
| Salmon Mtn Construction INC | Peter Louis Cafferata | astigma@astigmatic.com | (530) 925 4120 | GC, remodel, ADU | Forks Of Salmon · Siskiyou County | — | — |
| Samuel Alamillo Concrete And Masonry | Samuel Alamillo Concrete And Masonry | — | (530) 340 3801 | Other | Montague · Siskiyou County | — | — |
| Sarwas Const | Sarwas Const | — | (530) 426 4663 | GC, remodel, ADU | Mt Shasta · Siskiyou County | — | — |
| Schlumpberger General Engineering | Schlumpberger General Engineering | — | (530) 598 0297 | Other | Yreka · Siskiyou County | — | — |
| Scott Cassell Construction | Scott Stewart Cassell | — | (530) 925 9899 | GC, remodel, ADU | Mc Cloud · Siskiyou County | — | — |
| Scott River Builders | Scott River Builders | — | (530) 598 6881 | GC, remodel, ADU | Scott Bar · Siskiyou County | — | — |
| Scott River Pump And Irrigation INC | Ross Scott Smith | — | (530) 468 2916 | Electricians | Fort Jones · Siskiyou County | — | — |
| Scott Valley Construction | Albert Leon Fredric Branson | — | (530) 467 3910 | GC, remodel, ADU | Etna · Siskiyou County | — | — |
| Scott Valley Electric | Clinton Thomas Jones | — | (530) 467 3637 | Electricians | Etna · Siskiyou County | — | — |
| Shasta Premier Inspection Group | Shasta Premier Inspection Group | info@shastapremier.com | (530) 598-7856 | Inspectors | Yreka · Siskiyou County | — | — |
| Shasta River Milling | Shasta River Milling | — | (530) 598 8653 | GC, remodel, ADU | Yreka · Siskiyou County | — | — |
| Shasta Valley Electrical | Alberto Benjamin Iii Trujillo | — | (530) 643 1324 | Electricians | Yreka · Siskiyou County | — | — |
| Shed Horn Excavation Incorporated | Casey Gunner Hoff | — | (541) 619 9729 | Other | Yreka · Siskiyou County | — | — |
| Shekinah Floor Covering | Shekinah Floor Covering | — | (530) 859 2896 | Other | Dunsmuir · Siskiyou County | — | — |
| Showplace Services | Charles Steven Wilson | — | (530) 459 5327 | Windows, patio, painters | Montague · Siskiyou County | — | — |
| Sierra Gold | Jacob Charles Dick | info@sierragold.com | (530) 386 6615 | GC, remodel, ADU | Hornbrook · Siskiyou County | — | — |
| Silva General Contractors | David Lyn Silva | — | (530) 598 7075 | GC, remodel, ADU | Yreka · Siskiyou County | — | — |
| Simas Telecom | Simas Telecom | — | (530) 842 2441 | Other | Yreka · Siskiyou County | — | — |
| Simas' Greenthumb Landscapes INC | Larry Dean Simas | — | (530) 598 4459 | Windows, patio, painters | Yreka · Siskiyou County | — | — |
| Siskiyou 20/20 Window Cleaning | Siskiyou 20/20 Window Cleaning | — | (541) 944-0935 | Windows, patio, painters | Weed · Siskiyou County | — | — |
| Siskiyou Arts Museum | Siskiyou Arts Museum | — | (530) 235-4711 | Windows, patio, painters | Dunsmuir · Siskiyou County | — | — |
| Siskiyou Builders Exchange | Siskiyou Builders Exchange | — | (530) 331-9795 | Restoration | Yreka · Siskiyou County | — | — |
| Siskiyou Communications INC | Brenda Sue Kellog | — | (530) 467 6154 | Other | Etna · Siskiyou County | — | — |
| Siskiyou County Animal Control | Siskiyou County Animal Control | — | (530) 842-8123 | Pest, tile roofs | Yreka · Siskiyou County | — | — |
| Siskiyou County Construction | Robert Henry Tessmer | — | (541) 990 9985 | GC, remodel, ADU | Mt Shasta · Siskiyou County | — | — |
| Siskiyou Hydrokleen | Siskiyou Hydrokleen | kdunnauto@sbcglobal.net | — | HVAC | Yreka · Siskiyou County | — | — |