The Residential Building Code – Test Your Understanding of Some Common Issues

Below you’ll find an assortment of common code issues confronting residential builders. Do you know what call to make? Test yourself and see how well you know the code. We’ll use the International Residential Code as our answer guide.

by Paul Fisette – © 2006

Understanding and satisfying the building code can be confusing. To be fair, it is difficult to write one set of regulations that addresses every building condition. But having a reasonable level of code consistency would be helpful. Building codes are written as national models, but they are enforced locally. Recently, a director at the National Conference of States on Building Codes and Standards, informed me that there are more than 2000 different code interpretations in our country. It’s mind-boggling. To make matters worse, inspectors interpret the same code differently – even in states that have statewide codes. There is hope. The International Code Council is pitching its International Residential Code (IRC) as a national standard. And many communities are adopting this model. While many building professionals doubt that we will ever have a uniform code, many building code officials respect the IRC as a good code model. It provides a common language. So, using the IRC, let’s test our understanding of some common code issues.

1. True or False — Small holes and gaps around ductwork and plumbing penetrations are OK as long as they are not in an exterior wall.

Very few plumbers fill the holes they run pipes through. However, they are required to seal the holes, spaces and pathways as a fire-blocking requirement. Standard practice is to cut oversized holes to accommodate ductwork and piping runs. Section R 602.8 of the IRC outlines this code requirement. It states, “Fire blocking shall be provided to cut off all concealed draft openings (both vertical and horizontal) and to form an effective fire barrier between stories, and between a top story and roof space.” The IRC goes on to prescribe sealing 6 specific locations. Number 4 on the list is: “At openings around vents, pipes, and ducts at ceiling and floor level, with an approved material to resist the free passage of flame and products of combustion.” This issue also involves energy conservation and indoor-air quality.

2. True or False — Metal roof-framing connections are required only in high-wind zones.

The traditional practice of toe-nailing trusses to a wall’s top plate does not satisfy basic code requirements. Section 802.10.5 states that “Trusses shall be connected to wall plates by the use of approved connectors having a resistance to uplift of not less than 175 pounds and shall be installed in accordance with the manufacturer’s specifications.” Section 802.11.1 imposes further requirements for roof assemblies subject to wind uplift pressures of 20 psf or greater. An interesting side note is that the code does allow toe-nailing of roof rafters, but this is a complicated issue. It’s complicated because you must consider location, roof pitch, natural topography, building height, and constructed features of a building site to craft an adequate roof-fastening strategy. However, toe-nailing rafters is inadequate based on recently conducted research. Jim Cheng, Senior Research Analyst with State Farms Insurance Companies, concludes in his April 2004 Forest Products Journal article that toe-nailed connections fail at 90 mph wind loads found in most of the country. Cheng states, “Toe-nailed connections for the roof-to-wall system are not appropriate in wood-framed structures, and stronger connection methods for the uplift load resistance should be recommended.”

3. True or False — Steel reinforcement (rebar) isn’t required in continuous concrete footings and poured-concrete walls.

In general, steel reinforcement is not required in residential foundations. IRC subsections under R 403.1 outline footing requirements and those under R 404.1 deal with foundation walls. Tables R 404.1.1(1) – R 404.1.1(4) provide design guidelines that list a wide range of options for designing un-reinforced concrete foundation wall systems. While not all designs are exempt from rebar, the design guidelines are clearly written and chances are you will not need to use rebar. There are notable exceptions to this “Free Pass”, so you do have to review this code section carefully. And if you live on the West coast, all bets are off. You need rebar because of seismic exposure. In fact the seismic map [Figure R301.2(2)] reveals that most areas in the western US and a significant region in the Southeastern US require seismic reinforcing described in section R403.1.3.

4. True or False — Manufacturers’ span charts are suitable for designing engineered-floor frames.

I-joists and floor trusses are similar to roof trusses with regard to the code approval process. Sizes, spans, and performance values for specific products are not found in the building code. Builders must submit a drawing to the Building Official with the set of plans. IRC sections R502.1.4 and R502.11 provide clear guidance about what is required when engineered I-joists are used in a design. Some of the relevant code language states that “The truss design drawings shall be prepared by a registered professional…” and “Truss design drawings … shall be provided to the building official and approved prior to installation.” The design drawings must address including: span, spacing, bearing widths, design loads, connections and deflection ratios for live and dead loads. There is a list of 12 issues in all. While these requirements might be satisfied by a Faxed document, many inspectors will not accept a Faxed copy and require the submittal of plans that are “Wet Stamped” by an engineer.

5. True or False — Connecting roof-gutter downspouts to foundation perimeter drains is OK.

Section R903.4 prescribes drainage requirements only for those roofs that do not “… drain over roof edges.” Traditional pitched roofs do not need gutters and downspouts to satisfy code. On the other hand, section R405.1 does require foundation drainage and provides fairly elaborate direction due to the importance of keeping basements dry. Surprisingly, there is nothing in the code that prevents you from connecting downspouts to a foundation’s perimeter drainage system. The logical question stands: Why introduce all that roof water into such a sensitive location? To my mind, it makes no sense to inject water below grade to an area you are trying to drain. As a side note, you can’t discharge this drain water into either a septic system or municipal waste system. Downspouts and foundation perimeter drains must be connected to a separate storm sewer system.

6. True or False — Vented rain screens violate fire-blocking requirements.

In this case, the answer is not straightforward. Typically strips of furring are attached vertically over the wall sheathing and left open at the top and bottom. Siding is nailed to the furring strips. This creates an air space between the back of the siding and the face of the house-wrapped sheathing that drains and dries readily. It is highly effective, but there is 1 code issue to consider. Section R602.8 requires fire blocking to cut off all concealed draft openings “including furred spaces.” Cross blocks must be placed at the bottom, between stories, every 10 feet, and at the top near the roof. Installing all this cross blocking reduces airflow, drainage and drying. Many builders and building code officials think the spirit and intent of this code provision is not directed at vented rain screens, but rather at furred interior spaces. However, some inspectors disagree and think the code section holds as written. The code is not clear and the decision will be at the discretion of your local building inspector. So run your rain screen design past the inspector before building the walls.

7. True or False — Unvented “Hot Roof” designs for energy efficient cathedral roofs are illegal.

The code is clear. You need to ventilate roofs. This goes for both attic and cathedral roof frames. Section R806.1 states “…enclosed rafter spaces formed where ceilings are applied directly to the underside of the roof rafters shall have cross ventilation for each separate space…” Subsections under R806 provide specific guidance regarding the minimum vent area and clearance required. There are no exceptions provided in this section of the code, but this may not mean the case is closed. Building scientists have demonstrated that combining high levels of insulation with airtight detailing can provide superior, dry, durable cathedral roof construction without roof venting. Roof cavities filled with expanding foams or dense-packed cellulose have a winning track record for keeping roof cavities dry and functional. Call section R104.11 to the rescue. This section states, “An alternative material, design or methods of construction shall be approved where the building official finds the proposed design is satisfactory and complies with the intent and provisions of the code.” So the challenge is to convince the building inspector that your hot roof design works. Submit thoughtful details and copies of research reports that demonstrate hot-roof designs satisfy the intent of the code. This is a case-by-case and inspector-by-inspector decision so have a cooperative attitude and be prepared to answer questions about performance.

8. True or False — Code allows no more than 15% of wall area to be windows.

The code is flexible in this case. Section N1101.2.1 provides you with options. It prescribes code compliance by stating that buildings are limited to a glazing area that does not exceed 15% of the gross area of the exterior walls. However, this section also provides you with the opportunity to use performance-based solutions through the International Energy Conservation Code (IECC) for detached one- and two-family dwellings. The IECC performance-based approach is more complicated, but far more powerful regarding design choices. It allows you to consider the total building performance and energy tradeoffs are permitted. For example, you can compensate for extra glazing by using more insulation or other energy-saving design strategy to compensate for the energy lost by the additional glazing.

9. True or False — Vapor Barriers are required.

Moisture control is required in all framed walls, floors, and roof/ceilings of the building thermal envelope. IRC section R318.1 states, “…a vapor retarder shall be installed on the warm-in-winter side of the insulation.” However exceptions to the code are noted:

1) In construction where moisture or freezing will not damage the materials.
2) Where the framed cavity or space is ventilated to allow moisture to escape.
3) In counties identified with footnote in Table N1101.2

Language in section 502.1.1 of the IECC also talks about “…other approved means to avoid condensation in unventilated walls…” The intent of the code is abundantly clear: To control moisture and prevent damage to materials. Obviously, trapping moisture between the foundation wall and a plastic wall membrane is not a good building strategy. While there are several smart ways to design a basement makeover (see FHB # ??), the point here is you are not restricted by the code. You do need to demonstrate to the code official that your design approach is sensible.

10. True or False — Crawlspaces must be vented.

The building code treats crawlspaces as a special case, and they are subject to a different set of regulations than basements. Section R408.1 of the IRC regulates the ventilation of under-floor space. According to the IRC “The under-floor space between the bottom of the floor joists and the earth under any building (except space occupied by a basement or cellar) shall be provided with ventilation openings through foundation walls or exterior walls.” However, section R408.2 lists 5 exceptions. In general, building a code-accepted un-vented crawlspace is straightforward. For example, crawlspace vents are not required when continuously operated mechanical ventilation is provided in the crawlspace; nor are they required when you install a vapor-retarding groundcover, supply conditioned air to the crawlspace and insulate crawlspace walls according to the prescribed levels listed in section N1102.1.7.

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Last updated: April 1, 2009