How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

site-built, mobile/manufactured and modular homes

Are H-clips required by the building code for roof sheathing?

Wednesday, June 13, 2018

What H-Clips Do

H-clips provide additional stiffness between bearing points for the unsupported edges of wood panel (plywood or OSB) roof sheathing, along with the necessary 1/8” gap for expansion, as shown below illustrated on a bag of Simpson H-clips. Some older H-clips do not provide a built-in gap.

Not Always Required But A Good Idea

    Most builders install them, but they are not automatically required for all applications. The International Residential Code (IRC) and the Residential Edition of the Florida Building Code (FBC) both refer to Table R503.2.1.1(1) of the APA Engineered Wood Construction Guide for specs. H-clips are referred to in the APA Guide as “edge support."

    For the most common roof sheathing in our area, which is 1/2” nominal (7/16” actual) sheathing over trusses or rafters at 24” on center, there is no requirement for H-clips. The APA table has a span rating for the sheathing installed with, or without, H-clips, and the span rating is the same both ways. A low slope roof (below 2/12 pitch) at the same span is an exception, however, and an H-clip is specified. H-clips are also necessary for other wood panel thickness and span combinations. One or two H-clips will often allow a longer span between roof trusses/rafters.

    This is what the APA Engineered Wood Construction Guide has to say about H-clips:

    Their installation diagram also shows H-clips, although tongue-and-groove edges or blocking is noted as an alternative in the text above.

If The H-Clips Are Missing

    If H-clips are missing when you are walking on a roof, it is often discernible by the slight flexing when you step on an unsupported plywood edge. Also, H-clips reduce any buckling of those edges over time, so they are a good idea even if not always required. But, if your roof surface is sagging between trusses, lack of H-clips is only one potential culprit. Visit our blog post Why is my roof sheathing sagging between the trusses? for other possible causes.  

Diagnosing Other Roof Problems

    Also, see our blog posts What causes a sagging roof ridge line? and What causes a lump or dip in the roof? and What's the average lifespan of a roof?  

• • • • • • • • • • • • • • • • • • • • • 
Field Guide for Home Inspectors, a quick reference for finding the age of 154 brands of HVAC systems, water heaters, and electrical panels, plus 210 code standards for site-built and manufactured homes, and the life expectancy rating of 195 home components. Available at for $19.95.
• • • • • • • • • • • • • • • • • • • • • • 

  To learn more about roofs and attics, see these other blog posts:

• What are common problems of asphalt shingle roofs?

• When did Florida start requiring re-nailing of roof deck sheathing for a roof replacement?

How can I inspect my roof for hurricane damage?

• When were staples banned for roof sheathing attachment in Florida?

How can I tell if a roof has more than one layer of shingles? 

What are the common problems with attic insulation? 

What is the life expectancy of an asbestos cement shingle roof? 

What's the average lifespan of a roof?

Why is it a mistake to replace a roof and not replace its flashings? 

Why is there no attic access hatch in the house?

What is the building code requirement for an attic access hatch, scuttle, or door? 

Does a roof with multiple layers of shingles last longer?

What can I do to prevent roof leaks?

Are roof trusses better than roof rafters (stick framing)? 

Why is a popped nail in a shingle roof a problem? How do I fix it?

Do stains on the ceiling mean the roof is leaking?

 Why does my homeowner's insurance want a roof inspection?

What are the hazards to avoid when going into an attic? 

     Visit our ROOF AND ATTIC page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

Water Heaters

Water Heater Age

"What Are The

Signs Of..."

Septic Tank Systems

Structure and Rooms

Plumbing Pipes

Termites, Wood Rot

& Pests



When It First

Became Code

"Should I Buy A..."

Park Model Homes


Shingle Roofs




Wind Mitigation

Roof and Attic

"Does A Home


Pool and Spa

"What Is The Difference Between..."




Concrete and

Concrete Block

Metal Roofs


Modular Homes

Rain Gutters

Mold, Lead & Other Contaminants


Older and

Historic Houses

Crawl Spaces

Mobile-Manufactured Homes

Building Permits

Life Expectancy

Clay Soil





Exterior Walls

& Structures


Common Problems

HUD-Code for

Mobile Homes

Garages and Carports

Flat (Low Slope) Roofs

Electrical Panels

Sprinkler Systems

Electrical Receptacle Outlets

4-Point Inspections

Hurricane Resistance

Frequently Asked Questions (FAQ)

Home Inspection

Heating and Air Conditioning

Building Codes

Fireplaces and Chimneys

Inspector Licensing

& Standards

Energy Efficiency

Washers and Dryers



Doors and Windows



Electrical Wiring

Click Below  

for Links

to Collections

of Blog Posts

by Subject

Plumbing Drains

and Traps


Smoke & CO Alarms

Aging in Place

Top 5 results given instantly.

Click on magnifying glass

for all search results.






Air Conditioner & Furnace Age/Size


Electrical Switches





Water Intrusion

Electrical - Old

and Obsolete


Foundation Certifications

Tiny Houses

About McGarry and Madsen



Buying a home in North/Central Florida? Check our price for a  team inspection by two FL-licensed contractors and inspectors. Over 8,500 inspections completed in 20+ years. In a hurry? We will get it done for you.

Moisture Problems

Crawl Spaces