How do you fix an 18-foot garage door opening with a 1 and a half inch sag if it is made of two 2x12x20' with OSB in the middle?

Answer 1

QUICK & CHEAP FIX:

1. Jack it up one third in from both sides,just enough to get the center point about 1/16 inch above level. 2. Install a post at the center, and lower beam onto post. If necessary, replace a "swing up" garage door with a new roll up type.

BETTER FIX:

1. Remove door and trim. For safety, clear work area of storage and debris. 2. Attach a temporary beam to the ceiling joists a foot or two just inside of and paralell to the sagging beam. 3. Jack temporary beam up enough to take the load off of the old beam, plus about a quarter inch, at center. 4. Install & SECURE temporary shoring posts,and lower jack to allow all load to rest on the temporary shoring. 5. Remove nails holding old beam in place, or carefully cut them with a Saws All. 6. Remove the old beam, remove all old nails. 7. REINSTALL old beam, BUT FLIPPED OVER so the sag becomes an upward bow. If necessary, jack up more to get beam in. 8. Renail, or secure with deck screws. 9. Remove temporary shoring and lower load back onto reinstalled old beam. 10. Remove temporary beam and jack(s). 11. Reinstall door and trim. This fix will only be temporary until it sags again, but it could take years.

BEST FIX:

Follow steps 1 through 6. 7. Install a new 6x12 "engineered" Paralam beam. Paralams have a top side and a bottom side due to a built-in curve [prestressing] during manufacture. Install all prestressed beams with the bow upward. Finish with steps 8 through 11.

Answer 2

The above answer [1] is good, BUT I would first check with your local Building Department, OR a structural engineer for proper sizing of the glulam beam. To me, 6x12 seems too small for an 18 foot span. I would prefer to use a STEEL beam of the proper size. davew

There is another fix, IF the configuration of the structure allows it. By allow, that means if there is a gable [peak] over the door opening. 1. Jack the sagging beam, at the center, to just a bit ABOVE LEVEL [about 1/8 inch]. 2. Then, on the inside of the gable studs, FULLY SHEATH the entire stud wall with 1/2 inch plywood [do NOT use OSB or particle board]. Start at the center with a FULL SHEET(s) of plywood, and work outward. Don't skimp on fasteners [nails or deck screws]. Set fasteners on 6 inch centers, from top to bottom of EVERY stud. It wouldn't hurt to use a "healthy" bead of construction adhesive on all studs before applying the plywood.

Do not allow any gaps anywhere, from edge to edge, or from the top edge of the sagging beam to the lower edges of the end rafters. This "full" gusset is an amazingly strong reinforcement.

First answer by ID3486020742. Last edit by Johnny3h. Contributor trust: 525 [recommend contributor]. Question popularity: 75 [recommend question]