Best Practices Guide to Wood Siding Flashing Details at Joints & Corners
InspectAPedia^® -

Building wall corner siding flashing details & materials
Water leakage through the corners of building exteriors, cause, cure, prevention of siding or structural damage
Rain screen principle applied at the corners of building siding
Questions & answers about how to install flashing at building exterior walls or siding corners and trim boards

Wall corner siding & trim flashing details: this article gives specifications for proper flashing & sealing detailing at buildnig siding joints, corners, and window or door openings to provide an attractive and durable job that doesn't leak or rot.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers nor with topics or services discussed at this website.

© Copyright 2012 InspectAPedia.com, Daniel Friedman, Steve Bliss, Wiley & Sons, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website.

Wood Siding Flashing Details at Joints & Corners

This article series discusses best practices construction details for building exteriors, including water and air barriers, building flashing products & installation, wood siding material choices & installation, vinyl siding, stucco exteriors, building trim, exterior caulks and sealants, exterior building adhesives, and choices and application of exterior finishes on buildings: paints, stains. Also see Deck Flashing at Building and see FLASHING WALL DETAILS and FLASHING MEMBRANES PEEL & STICK. Adapted/paraphrased with permission from Best Practices Guide to Residential Construction. Steven Bliss.

Proper detailing at joints, corners, and openings makes for an attractive and durable job. Key details follow: Lap Joints. The IRC requires that horizontal lap sidings have a minimum one-inch lap joint, or 1/2 inch if the siding is rabbeted.

Weather-proofing Butt Joints in Building Siding

Figure 1-12: Splines under bevel siding joints (C) Wiley and Sons - S Bliss

In most climates, it is a good idea to slip a small spline of asphalt-felt paper behind each butt joint in horizontal sidings.

Layer the spline so it overlaps the piece of siding below, directing any water out onto the siding (see Figure 1-12 at left).

All end grain in the siding should be sealed after cutting with a water-repellent preservative (WRP) or primer.

Building Siding Flashing & Finish Details for Building Corners

Figure 1-5: corner board details (C) Wiley and Sons - S Bliss

Use overlapping 1x4s or 1x6s at outside corners or use 5/4 stock for a heavier look. Use a felt paper spline, wrapped around the corner and extending 6 inches beyond the corner board, to protect the joints where the siding meets the corner boards (see Figure 1-5 at left).

Use a square length of 5/4 stock at inside corners with a spline underneath. All end grain in the siding should be sealed after cutting with a water-repellent preservative (WRP) or primer.

With the spline, there is no need to caulk the joint. With no caulk, the joint is free to dry out when wet.

Flashing Details for Windows and Doors

If windows and doors are properly protected with splines of felt or flashing tape, there is no need to caulk the joints where siding meets the side casings.

At the top of a door or window, always direct the sheathing wrap over the head flange or cap flashing. Never caulk the joint between the siding and the head casing or the sill, leaving these joints open to drain any trapped water.

Also see WINDOWS & DOORS.

Siding Details At Roof-Wall Joint Step Flashings to Avoid Rot

Roof Wall Flashing Detail (C) Wiley and Sons - S Bliss

Roof Wall Flashing Detail (C)Daniel Friedman

Stop wood sidings at least 1 inch short of the bottom leg at step flashings and other roof flashings.

Otherwise water will wick up into the flashing leading to paint failures and decay (see Figure 1-6 above left). Our wall siding photo (above right) shows the beginning of deteriorating wood clapboards that were installed touching the surface of an abutting lower asphalt shingle roof.

ALso see RAIN SPLASH-UP SIDING DAMAGE.

Vertical and Plywood Siding Butt Joint Details

Figure 1-13: Joints in vertical and plywood siding (C) Wiley and Sons - S Bliss

Avoid horizontal butt joints in vertical siding. Where a butt joint is necessary, use a scarf joint sloped down toward the building’s exterior.

With plywood sidings, use a Z flashing at horizontal joints to shed water to the outside (see Figure 1-13 at left).

-- Adapted with permission from Best Practices Guide to Residential Construction.

Questions & Answers regarding this article

Questions & answers about how to install flashing at building exterior walls, siding, windows, doors, trim.

Ask a Question or Search InspectAPedia

HTML Comment Box is loading comments...

Recommend / Share this Article

...

Technical Reviewers & References

InspectAPedia.com^® - Daniel Friedman - Publisher & Editor.
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education. Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
InspectAPedia Bookstore lists recommended books, organized by topic & available for purchase. Most of our articles also include a list of recommended books for the specific article topic as well as other references, and information sources.
Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
Additional technical contributors & reference sources for this article are listed below.

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

FLASHING, ASPHALT SHINGLE VALLEYS
FLASHING MEMBRANES PEEL & STICK
FLASHING for METAL ROOFS
FLASHING ROOF WALL DETAILS
FLASHING ROOF-WALL SNAFU
FLASHING SIDING DETAILS
FLASHING WALL DETAILS
FLASHING WOOD ROOF DETAILS

VAPOR BARRIERS & CONDENSATION in buildings

WATER BARRIERS, EXTERIOR BUILDING
WATER ENTRY in buildings

Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Amazon.com and also Wiley.com. See our book review of this publication.
Decks and Porches, the JLC Guide to, Best Practices for Outdoor Spaces, Steve Bliss (Editor), The Journal of Light Construction, Williston VT, 2010 ISBN 10: 1-928580-42-4, ISBN 13: 978-1-928580-42-3, available from Amazon.com
Paul Galow - technical consultant on networking, LAN design, applications support. Galow Consulting Services, 914-204-1749, email: paulgalow@galowconsulting.com
John Rudy, Advantage Home Inspections, Flemington N.J. 08822 home inspector, 908-806- 6364, Home, Radon & Termite Inspections, Central & Parts of North New Jersey, email: jonadvantage1@yahoo.com

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
The Journal of Light Construction has generously given reprint permission to InspectAPedia.com for this article. All rights and contents are ©Journal of Light Construction and may not be reproduced in any form.
...

Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair

Ask a Question or Search InspectAPedia

Wood Siding Flashing Details at Joints & Corners

Weather-proofing Butt Joints in Building Siding

Building Siding Flashing & Finish Details for Building Corners

Flashing Details for Windows and Doors

Siding Details At Roof-Wall Joint Step Flashings to Avoid Rot

Vertical and Plywood Siding Butt Joint Details

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair