Birdmouths on Rafters – Neccessary? JLC question answered

Download PDF version (249.7k) Log In or Register to view the full article as a PDF document.
Why are we still cutting birdsmouths in rafters? We now have power tools that can easily rip a continuous beveled strip that can be added to the top plate to attach the rafters. Plus, we have steel connectors to ensure the attachment.

A.Mark McKenzie, an engineer in Brewster, Mass., responds: Although this alternative framing method could work in some instances, I think that the issues raised outweigh the benefits when compared with conventional (and properly executed) birdsmouth rafter cuts.

To begin with, how well the rafter was attached would depend directly on how well the ripped strip was attached to the plate, which would require an engineered attachment schedule to ensure that the ripped strip stayed put. And my guess is that the narrow strip would most likely split when you tried to nail through it.

Another problem with this method occurs when the rafters attach to the top of a wall instead of to a plate on the floor deck. The angled strip on top of the wall plates would prevent the ceiling/attic joists from bearing properly on the top plate, and the strip itself would not provide adequate bearing for those joists. Placing the joists on the strip above the plate would also make it more difficult to attach the top edge of the wallboard.

Structurally, a rafter sitting on an angular bearing point (the inclined plane of the ripped strip) would require that the rafter-plate connection deal with the horizontal and vertical components of the force differently than with a birdsmouth. A lot of force is transferred down the length of the rafter, and the seat cut on the birdsmouth transfers that force directly to the top plate. With the ripped strip installation, there would be no horizontal bearing surface to resist that force. Granted, a structural ridge can lessen the amount of force on a rafter — but even then, I would not attempt a ripped-strip rafter installation without having the entire system approved by an engineer.

The solution of simply adding metal clips can also be problematic. Again, an engineer should be consulted to ensure that any metal clips used are rated for the additional loading from the elimination of the birdsmouth, in addition to dealing with any standard regional conditions such as wind uplift or seismic.

In general, while the ripped-strip installation does eliminate the need to make two cuts for the birdsmouth, it’s debatable whether there are any real labor savings. Ripping the attachment strip requires a completely different setup with a different tool, whereas most framers I know cut the birdsmouths as just a small additional part of rafter-cutting “production.” Those two cuts add just a few seconds to the whole process.

As a final admonition, make sure that any framing detail — such as the rafter-plate connection — is done in a properly engineered manner. It’s always better to have an engineer review and approve your methods before you start cutting and nailing.

Methuen Drywall Mold

METHUEN — Water that leaked into the new high school auditorium this spring caused the construction contractor to remove some drywall and work on an elevator shaft, work that will not be billed to the city.

Consigli Construction removed the bottom two feet of drywall in the new auditorium under construction after heavy rains this spring as a preventative measure, said Gino Baroni of Trident Building and Properties Group, the project manager overseeing the nearly $100 million renovation and expansion of the high school.

“This is part of the normal construction process,” Baroni said. “The contractor was proactive and took care of it.”

The drywall was removed and an industrial hygienist was present for the work, he said. Some work is still to be finished on an elevator shaft. The space will be cleared and certified before people can use the space.

Consigli will absorb the cost of the work. “It’s going to be their contingency or cost because it was not caused or created by the owner,” Baroni said.

He and several Methuen officials said the newly renovated and expanded southern portion of the high school is on track to open for students on Sept 4.

Superintendent Judith Scannell said construction crews have “ramped up their workers” for the home stretch and the building’s custodial staff was asked to work second shift for cleanup.

“It’s very busy and we will get there, but it’s that push-comes-to-shove time,” she said yesterday.

Construction began in earnest last summer, when a total renovation of the south wing and the addition of a new wing began. The new wing includes a media center, a cafeteria, an auditorium and fine arts classrooms. Students in grades 10 through 12 took classes in the north wing while that construction was ongoing.

This year, students in those grades are to move into the new section while work begins on the north wing.

Ninth graders are housed at Central School on Ditson Place.

The entire school is scheduled to be completed by next summer.

Follow Douglas Moser on Twitter @EagleEyeMoser. To comment on stories and see what others are saying, log on to

DCA-6 Revised is Available

American Wood Council Updates Deck Design Guide

Official new values for the strength and stiffness of Southern Pine have now taken effect, and they mean shorter spans for the wood species that accounts for most treated wood in the marketplace. Taking the new values for treated SYP into account, the American Wood Council has updated its “Prescriptive Residential Wood Deck Construction Guide” with new span tables and fastener requirements.

Just Google DCA-6 to find.

JLC Online – Home Ventilation Issues

Home Ventilation Rules
By Ted Cushman
Be the first to comment

The American Society of Heating, Refrigeration and Air-conditioning Engineers (ASHRAE) published its Standard 62.2, “Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings,” in 2003, issued a revised version in 2007, and released the current version in 2010. The 2013 edition should be out soon.

ASHRAE 62.2 is referenced in state building codes, and it’s used by manufacturers to size their equipment and ductwork. It’s the subject of a comprehensive training package offered by the Federal Government’s Weatherization Assistance Program Technical Assistance Center. But is it right? Maybe … and maybe not, says building scientist Joseph Lstiburek.

In an interview with energy rater Allison Bailes published on Bailes’ “Energy Vanguard” blog (“Interview with Dr. Joe Lstiburek — The Ventilation Debate Continues”) Lstiburek said a little more than that, in fact. Bailes sums up Lstiburek’s attack on ASHRAE 62.2 like this: “He contends that the residential ventilation standard, ASHRAE 62.2, ventilates at too high a rate, causing problems with humidity in hot or mixed humid climates, comfort and dryness in cold climates, and too much energy use everywhere. The 2013 version makes it worse.”

Talking with Bailes, Lstiburek said that the ventilation rates called for in ASHRAE 62.2 are excessive: “We know that houses ventilated at the 62.2 rate lead to comfort problems in cold climates by drying out the building and drying out furnishings. We know that ventilating at the 62.2 rates in houses built to the Model Energy Code lead to part-load humidity problems. We know for a fact that these rates lead to humidity problems in the South and dryness and comfort issues in the North, so that’s not a guess. We know this from experience.”

And Lstiburek says homes have historically performed well at lower air change rates: “We also know that millions of houses were constructed in the 1990s and 2000s that were between 3 and 5 air changes per hour at 50 Pascals with no ventilation systems and their air change rates are between 0.2 and 0.3 air changes per hour as tested by tracer gas work and that’s consistent with houses tested in the ’70s and ’80s as well. The myth of the old leaky house is just a myth. These houses had no ventilation systems in them at all and they’re not suffering from indoor air quality problems because nobody’s measured any contaminants. There’s no measurements.”

Tamper Resistant Access Ports on Outdoor A/C Equipment

Did you know that the 2009 IMC and IRC require that all outdoor ports on A/C and refrigerant equipment must be made tamper resistant?

Why? Kids have been ‘huffing’ Freon out of these to get high. They place a plastic bag over their head and fill it with Freon from A/C units. Sadly, it can kill easily by displacing all of the Oxygen in the bag.

See for more info.

Carpe Diem Holyoke

Holyoke sets city record by seizing $1.2M in property from delinquent taxpayers

Mike Plaisance, The Spingfield Republican
More than $1.2 million was collected in delinquent taxes from property owners in the previous fiscal year to set a city record, Treasurer Jon D. Lumbra said.
“We got more aggressive. We got outside counsel to assist us,” Lumbra said Wednesday.
Between June 30, 2012 and July 1 of this year, the city seized $1,208,499 in delinquent taxes, fees and charges from 30 owners who by paying avoided losing their properties, he said.
The previous record seized was $745,464 in fiscal year 2004, he said.
The city hired the law firm of Siddall & Siddall of Springfield, which specializes in state Land Court cases. A benefit is that while the city paid the lawyers $75,000, the money is recouped by adding it to the fees that must be paid by the delinquent property owners, he said.
The $1.2 million will be included in the state Department of Revenue calculations that will determine how much of a free cash fund will be available to the city in the current fiscal year. That determination usually is announced in September, he said.
“At a time with such financial restraints within the city budget, it’s important that we do everything we can to collect these funds before asking those taxpayers that pay on time to increase their burden,” Lumbra said
The collection of back taxes is an effort by the city to be aggressive, said Mayor Alex B. Morse, who noted the city also held the first public auction of properties seized for nonpayment of taxes in April in nearly 40 years.
“Folks, taxpayers, should understand our ability to collect that money mitigates any tax increase, goes back into the general fund and into free cash, which we can reinvest in the community, which benefits everybody,” Morse said.
The amount of delinquent taxes collected in fiscal year 2011 was $381,377; fiscal year 2010, $231,413; fiscal year 2009, $317,233; fiscal year 2008, $290,134; fiscal year 2007, $492,351; fiscal year 2006, $223,587; fiscal year 2005, $210,793, and fiscal year 2004, $745,464.
Related links: Economic Snapshot
Industries: Commercial Real Estate

Timing is Everything in Framingham

By Danielle Ameden/Daily News staff
The MetroWest Daily News
Posted Aug 15, 2013 @ 12:01 AM

Related Stories
Framingham construction firm appeals cease and desist order
Framingham neighbors to protest asphalt grinding operation tonight
Building official denies Ellingwood permit in Framingham
A local construction firm contested an order to stop crushing asphalt too late for the Zoning Board of Appeals to take it up, the board ruled Tuesday.
The ZBA didn’t get to the merit of Ellingwood Construction’s appeal. It instead voted, 3-0, that the firm didn’t meet the threshold for jurisdiction, Administrator Gene Kennedy said.
“It’s for the lawyers to determine what the next step is,” Kennedy said.
Ellingwood asked the ZBA to overturn Building Commissioner Michael Tusino’s cease-and-desist order to stop hauling in and grinding asphalt, brick and concrete at 145 Meadow St., off Old Connecticut Path. Tusino said the recycling operation isn’t allowed in the residential zone, or eligible for the same grandfathering protection as the contractor’s yard Ellingwood operates there.
Under the town’s zoning bylaw, applicants have 30 days to file an appeal of a building commissioner’s order directly with the town clerk, Kennedy said.
In this case, Tusino issued his order on May 20, and gave Ellingwood 14 days to comply.
Firm owner William Ellingwood signed an application for a public hearing on June 17. Timestamps show the ZBA office received it on June 21, but it wasn’t stamped in by the town clerk’s office until July 8.
Kennedy said Ellingwood dropped off the paperwork with his office instead of bringing it to the town clerk’s office in time.
The town started scrutinizing the firm’s operations after neighbors came forward, saying dust, noise, debris and other aspects of the trucking operation was harming their health and quality of life.
Ellingwood’s attorney David Klebanoff could not be reached Wednesday for comment.

Read more:
Under Creative Commons License: Attribution Non-Commercial
Follow us: @metrowestdaily on Twitter | MetroWestDailyNews on Facebook

Time Magazine – Buildings as Weapons of Mass Destruction

How Shoddily Constructed Buildings Become Weapons of Mass Destruction

We tend to focus on the size of an earthquake, but death toll has more to do with the quality of buildings. A new study shows that countries in south-central Asia are on the wrong side of the disaster divide — and the costs could be terrible

By Bryan Walsh @bryanrwalshAug. 12, 20135 Comments

Read Later

Poorly constructed buildings were responsible for the massive death toll of the 2010 Haiti quake

Email Print Share Comment
Follow @TIME
There’s a term I’ve written about in the past: the disaster divide. It refers to the vast discrepancy between developed and developing nations in the death toll from natural disasters. Those countries that prepare for hurricanes or earthquakes and have the resources to respond to a catastrophe can now weather even very severe events with relatively little loss of life. The same storm or quake in a poor country, however, can cause massive human loss. That’s why the Bay Area can suffer a 6.9 quake in 1989 and lose just 63 people, while Haiti can suffer a quake just a bit stronger in 2010 and lose at least 100,000 people. Poverty — and even more, poor governance and corruption — is the multiplier of natural disasters.

That’s why one of the most vulnerable places in the world is south-central Asia. A quarter of the world’s population lives in the region, which runs roughly from Iran in the west to Burma in the east. These countries are in seismological peril — they sit on the northern edge of the Arabian and Indian plates, which are colliding with the southern margin of the Eurasian plate. There have been huge earthquakes recorded throughout history in these countries, with one temblor in 2005 killing over 80,000 people in India and Pakistan’s disputed Kashmir region. There will surely be powerful quakes there in the future.

(PHOTOS: A Final Embrace: The Most Haunting Photograph from Bangladesh)

But the danger isn’t just seismological. As Roger Bilham and Vinod Gaur pointed out in Science last week, the poorly constructed buildings that are common throughout the region — especially the multistory residences that can and do collapse like pancakes in a quake — amplify that danger:

Postseismic investigations reveal that structural collapse is typically attributable to shoddy construction resulting from poverty and ignorance, or to covert avoidance of building codes by contractors. Moreover, earthquake-resistant design codes, where they exist, are generally applied to civic structures only, and not to the dwellings where most of the people of South Asia live. Pervasive building fragility is all too frequently highlighted by the spontaneous collapse of multistory structures in the major cities of South Asia. During strong earthquakes, widespread building collapse is not only expected but also statistically quanti?able within minutes of the main shock and is used to aid search and rescue.
Bilham and Gaur go on to worry specifically about the vulnerability of nuclear power plants in India to future quakes — a fear I share. (U.S. nuclear plants aren’t exempt from seismic risks either.) But the greatest risk comes from those all-too-fragile apartments and office buildings that can be found in cities throughout south-central Asia. When a strong quake hits, those buildings become tombs of rubble. That’s exactly what happened in Haiti and in the terrible 2008 quake in the Chinese province of Sichuan, which killed over 80,000 people — many of them young children whose substandard schools collapsed around them. The earthquakes are the gun. But the buildings are the bullets.

There’s nothing the countries of south-central Asia can do about seismic risks. That’s a fact of geography. But stricter building codes — and perhaps more important, actually enforcing those building codes — can take the edge off that risk, and keep the next big quake from becoming a human catastrophe. Obviously poverty is a challenge, but the work of organizations like Architecture for Humanity and the Appropriate Infrastructure Development Group demonstrate that you can build more-resilient structures without busting even a poor country’s budget. And better building is a perfect use of development aid, which always tends to be overly weighted to relief instead of resilience. Better to spend the money now — and save lives later.

Read more: