How to Repair a Sagging Barn Roof: Illustrated Guide
The Barn Featured in This Article
How Much Repair Is Needed?
The barn in question is not in horrible condition. But it was well on its way to becoming dilapidated, and would eventually have fallen in on itself if proper repairs had not been attended to.
It sickens me every time I see an old building being let go, so I was pleased when my husband and I were called to do this repair. The barn was still being used for animals and equipment storage, and had all the marks of a long, evolving life.
Some roofs will be worse than this one, and will necessitate more tools, time, and materials to put right. This fix took about half a day. If your roof is seriously sagging, you may need a come-along in order to winch the sides of your building back in place, before you add bracing. Some barns require at least one come-along as a permanent fixture, strung across the haymow, to keep them from continuing to buckle outward.
If I get a chance, I will add photos of a repair of this type. But for now, hopefully these pictures and instructions will help you.
The Extent of the Damages to the Barn Roof
Tools and Supplies
- Carpenter's pencil
- Circular saw
- Chalk box, optional
- Nail gun
- 16-penny cement-coated nails for use with all lumber (nail gun strips)
- 2-inch roofing nails for plywood . . .
- . . . or 8-penny nail gun nails, 12-penny if you prefer
- Screw gun, if needed
- 2x6 lumber--amount will vary according to your situation
- OSB board or plywood at least 1/2-inch thick--number of sheets will vary. 5/8-inch or 9/16-inch thick is better.
- Replacement roof materials and corresponding hardware, if needed
- Imagination, sense of humour, good temper, patience, common sense
If Installing Metal Roof Sheets
- 2-inch sheet metal screws
- Screw gun
- Appropriate metal roof sheets
- Tin snips
- Electric metal shears, optional--if needing to trim sheets lengthwise, they make the job clean and fast, especially on high ribs
- Square or straight edge, for marking screw lines across sheets in line with purlins
Overview of Construction Process
Your goal is to strengthen and reshape the roof through means of wooden braces, 2x6 lumber, possibly new or added purlins, and maybe a come-along manual winch. You will use a hydraulic floor jack to lift a long 2x6 against strategic points along the roof to nudge the roof back into shape. Then you will make triangle-shaped braces from plywood or OSB, and install them under the ridge. If needed, a come-along can gently be used to help pull the barn into shape by hooking it to the walls.
After these changes, your barn should maintain its shape well enough not to be a danger to occupants, and you should be able to follow up with other roof or structure repairs.
Stage 1, Step 1--Jacking Up the First Section of Roof; Placing the Bottom Part of the First Brace
There is no magic to making triangle braces. Careful measurements and a reasonably snug fit are required, but beyond this, what you need to do is whatever works.
The 2x6 lumber itself does not substantially hold the barn; the triangle of plywood or OSB does that. The lumber is there mostly to stabilize the triangle, which will in turn uphold and shape the barn roof (and hence walls, etc.)
Stage 1, Step 2--Cutting and Placing the Plywood Triangle on Brace #1
The first section is complete. The next, and the next should be very like it.
You will keep reshaping the roof a bit at a time with the long board and hydraulic jack, pausing to make more custom braces as you go.
Stage 2, Step 1--Moving the Jack to the Next Joist
Holes Along the Ridge
How much gap needs to be sucked out along the ridge in order for your ridge cap to work properly? In new construction, a gap up to 4 inches wide is sometimes left. However, in this repair, we tried to remove all the gap we could, resulting in 2 to 3 inches toward the peak of the barn.
If you get any gaps down to 2 inches, your building should become weather tight with proper installation of new ridge cap, and foam closure strips. Ridge cap trim is usually a total of 11 inches wide.
Stage 2, Step 2--Re-Aligning the Next Section of Roof Ridge
Each brace's measurements is likely be slightly different than the one before, and you should never assume that what you did for the first brace will serve for the others. Treat each as an individual, just as you did the first.
Stage 2, Step 3 - Finishing the Second Brace
The roof is looking much better than it did at the beginning of the project, but is only about half done. More bracing is required, also purlins, roof sheets, and replacement ridge cap.
Stage 3 - Jacking Up and Bracing the Third Section
More bracing can be put where needed. In our case, we installed new purlins between rafters toward the front of the barn, where the entire structure had disintegrated, and metal roof sheets had disappeared.
This fix was fairly straightforward, but if yours is trickier, use whatever ingenuity you need to in order to make your building safe and reliable.
Stage 4 - Adding Additional Bracing Along the Roof Slope
The Roof Is Back Where It Ought to Be
More Damage=More Bracing
The steps shown here can be repeated as far along your roof as necessary. Continue jacking, bracing, and aligning through all the affected roof sections.
We haven't had a call-back, and the customer seems satisfied whenever we see him around, so we can say that this has been a successful repair!
My husband added new ridge cap and gable trim to this barn at a later date, but no photos are available.
Using a Come-Along
If a come-along is required in order to pull the barn together enough for the roof to meet, the following is a good way to attach it.
Insert lag bolts near the ends of two lengths of ⅜-inch or ½-inch diameter chain, securing the chains to the insides of your barn loft walls opposite each other. The chains should have hooks. Secure your come-along between the chains, and draw the barn back together by degrees.
If your barn starts to creak, groan, pop, or yell excessively--STOP! You can wait several hours or a couple of days, wait for adjustments to take place, and pull the building together a little more. A building whose bones hurt may require several days to put to rights.
Whatever you do, please use common sense, and don't damage your barn further, or cause it to collapse on anyone.
A come-along can be used in conjunction with the jacking method shown here.
If you believe your barn may not be fixed permanently by merely installing braces, you may install at least one come-along permanently in the hay mow. There are also alternate ways of creating braces which will be out of the way of most activities. We will cover at least one of these ways which was used in a different local barn, and add that information to this article.
King County Barn Preservation Program
Restored Barn Transformed Into a Home
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
© 2019 Joilene Rasmussen