Expanding Your Roof? How to Tie-In Properly

Adding extra space to your home often requires expanding your roof. But tying a new roof into an existing one can be a complex process that shouldn't be attempted without careful planning and preparation. By assessing your current roof, sizing and preparing the new section properly, seamlessly joining the roofs, and cleanly finishing the project, homeowners can successfully tie in a roof addition themselves.

Assess the Current Roof

Before modifying your roof, you need to fully examine its current state. This includes:

• Inspecting the roof decking and structure for any issues that may impact the project or your home's structural integrity.
• Identifying the specific connection points between the old and new roofs based on your planned addition.
• Checking for any rot, leaks, damage, or weaknesses that need repairing before attempting the tie-in.

Thoroughly assessing potential tie-in locations on your existing roof helps ensure the project goes smoothly. It also allows you to spot any repairs needed beforehand to avoid bigger issues down the road.

Examining the Roof Deck and Structure

The roof deck refers to the sheathing or boards that sit atop your roof trusses or rafters. This provides the base for your shingles or other roofing material. When tying in a new roof, you'll likely need to remove areas of the deck to access the necessary framing.

So examine the deck carefully, watching for:

• Rotten, damaged, or deteriorating boards that will need replacing.
• Nail pops or other issues that suggest underlying structural problems.
• Signs the deck can't support the weight of new construction materials or activities.

Also closely inspect the actual roof structure like the trusses and rafters. The framing must be in good shape to bear the load of the roof addition. If the structure seems questionable or you're unsure, consult a structural engineer before proceeding.

Pinpointing Connection Points

Tying in a new roof section requires carefully planning where it will meet the existing structure. Identify where:

• The last truss or rafter of the old roof is located.
• You'll attach new trusses and join roof decking or sheathing.
• Flashing, shingles, valleys and ridges will intersect.

Marking these connection points with chalk lines guides the removal of roofing materials and framing. It also helps align new components during assembly. Just be sure measurements are precisely made to achieve proper roof slopes and water runoff.

Checking for Damage and Decay

Scan roof surfaces, edges and overhangs for any issues requiring repair before the project begins. Watch for:

• Missing, cracked, curled or broken shingles.
• Deteriorating or poorly sealed areas prone to leaks.
• Sections with moisture damage or rot from prior leaks.
• Exposed underlayment or felt indicating shingle loss.

Repairing damage ahead of the roof tie-in prevents bigger headaches later. It also lets you spot leaks to address their underlying cause first. Taking this step improves waterproofing for the entire roof during and after construction.

Prepare the New Roof Section

With assessment complete, the real construction work begins...

Sizing and Cutting Materials

Measure carefully to size all necessary roofing components before assembly. This includes:

• Trusses spaced according to your roof's dimensions and design.
• Decking boards cut to length between trusses and trimmer joists.
• Flashing that fits connection points and valleys precisely.
• Shingles that overlap correctly along roof edges and ridges.

Having properly measured materials avoids delays and complications erecting the new roof section. It also lets you pre-cut pieces ahead of time for faster assembly. Just remember to factor the right slopes and overlaps so water sheds properly from roof surfaces.

Installing Underlayment and Flashings

Before shingling, waterproof the new roof section by laying synthetic underlayment or roofing felt paper across the decking. Carefully fit flashing along wall edges, valleys and protrusions through the roof. This seals vulnerable areas prone to leaks from wind-driven rain and melting snow.

Proper underlayment and flashing prevents moisture issues in the future. It also improves shingle longevity by shielding them from excess water exposure as they age and deteriorate.

Attaching Drip and Rake Edges

Drip edge gets installed along eaves and rake edge along gable ends prior to shingling. These angled metal strips help guide water off roof edges into gutters instead of seeping into the deck or walls.

Fit drip edge precisely along the roof's lower edge overhanging the fascia board. Rake edge attaches to gable end boards bordering the roof's triangular peak. Proper placement is key so runoff hits the edge versus sheathing or siding.

Join the Roofs

With prep work done, it's time for the main event...

Lining Up Shingles and Edges

When joining roofs, carefully align where:

• The last course of old shingles meets the new roofline's first row.
• Valleys and ridge lines intersect between both sections.
• Flashing from each roof joins together.

Proper alignment provides an even, continuous appearance across the entire roof. It also ensures consistent overlaps so water sheds properly without getting trapped between loose shingles or gaps.

Attaching the Roofs

With materials positioned correctly, physically connect the roofs using:

• Roofing nails driven through overlapping shingles every few inches.
• Roof sealant applied liberally beneath shingles and along seams to prevent moisture entry.

Securely fastening shingles together with plenty of nails prevents wind or storms from lifting edges or corners. Sealant offers additional leakage protection along vulnerable intersections prone to separation.

Extending Valleys and Ridges

Where roof planes meet to form valleys and the high point of ridges, these areas need proper extension between old and new sections. This ensures continuous slopes and water flow without interruption.

For valleys, fold the woven closure strip or metal flashing over top the old roof a minimum 12 inches. Ridge vent caps or rolled ridge flashing should overlap the existing ridge point by at least 6 inches.

Achieving Proper Slope

Consistent slope and drainage prevents pooled water that can leak through shingles or flashings. Carefully gauge slopes when joining roofs so runoff flows evenly from old surfaces across new.

Tie-in points with uneven planes or gaps can trap moisture and debris. So double-check aligning measurements to maintain slope consistency across the entire roof.

Complete the Project

You're in the home stretch! Just a few more steps...

Installing Caps and Vents

Finish ridge lines using ridge vent caps that protect intersections while allowing hot air to escape. Place caps over top overlapping ridge flashing, centering the vent opening over ridges.

Also install any plumbing or attic vent stacks that protrude through the new roof section. Frame openings, flash properly, then seal with vent caps fitted snugly around pipes.