MHIC Building Codes and Standards 4 — Questions and Answers
Question 1: Under the International Energy Conservation Code (IECC) as adopted in Maryland, what is the minimum insulation R-value required for an attic in Climate Zone 4 (where most of Maryland falls)?
- R-30
- R-38
- R-49 (Correct answer)
- R-60
Correct answer: R-49
Maryland's Climate Zone 4 requires a minimum of R-49 insulation in attics per the IECC. This higher R-value reflects the need for energy efficiency in a mixed-humid climate with cold winters. R-30 and R-38 are insufficient for this zone, and R-60 exceeds the minimum requirement.
Question 2: According to the International Residential Code (IRC), what is the minimum required fire separation distance between a newly constructed detached garage and the main dwelling on the same property?
- No separation required if the garage is detached (Correct answer)
- 3 feet
- 5 feet
- 10 feet
Correct answer: No separation required if the garage is detached
The IRC does not require a fire-resistance-rated separation between a detached accessory garage and the main dwelling as long as it is truly detached (not connected by a breezeway or shared wall). Fire separation requirements only apply to attached garages, which require 1/2-inch Type X drywall on garage-side walls and ceilings.
Question 3: A homeowner is adding a bedroom in the basement. Under the IRC, what is the minimum net clear opening required for an emergency escape and rescue window (egress window) in that bedroom?
- 3.3 square feet
- 4.0 square feet
- 5.7 square feet (Correct answer)
- 6.2 square feet
Correct answer: 5.7 square feet
The IRC requires emergency escape and rescue openings to have a minimum net clear opening of 5.7 square feet for below-grade windows (e.g., basement bedrooms). Above-grade windows require a minimum of 5.0 square feet. The opening must also be at least 24 inches in height and 20 inches in width.
Question 4: Under the IRC, when installing a wood-framed deck attached to a house, what is the required fastener for connecting the ledger board to the house rim joist to resist lateral (horizontal) forces?
- Two 16d common nails per joist bay
- Approved lag screws or bolts with specified spacing (Correct answer)
- Construction adhesive plus 10d nails at 6 inches on center
- Simpson Strong-Tie LUS joist hangers only
Correct answer: Approved lag screws or bolts with specified spacing
The IRC requires ledger boards to be attached with approved lag screws or through-bolts sized and spaced according to the deck load tables in the code. Simple nails are insufficient to resist the lateral and withdrawal forces placed on a deck ledger. The specific size and spacing depends on joist span and species of lumber per IRC Table R507.9.1.3(1).
Question 5: Maryland adopted the International Residential Code with local amendments. When a Maryland local jurisdiction's amendment conflicts with the state-adopted IRC, which takes precedence for a licensed MHIC contractor?
- Always the IRC, because it is the parent code
- Always the local amendment, because local codes are stricter
- The more restrictive requirement between the IRC and the local amendment (Correct answer)
- The contractor may choose whichever standard is easier to meet
Correct answer: The more restrictive requirement between the IRC and the local amendment
In Maryland, when a local jurisdiction adopts amendments to the state-adopted IRC, contractors must comply with the more restrictive of the two requirements. Local amendments typically make provisions stricter to address regional conditions. A contractor cannot choose the less demanding standard — compliance with the higher bar protects the homeowner and ensures the contractor meets all applicable law.
Question 6: According to the IRC, what is the maximum allowable rise (vertical height) for a single stair riser in a residential interior staircase?
- 6 inches
- 7 inches
- 7-3/4 inches (Correct answer)
- 8-1/4 inches
Correct answer: 7-3/4 inches
The IRC permits a maximum riser height of 7-3/4 inches for interior residential stairs. The minimum is 4 inches. Additionally, the greatest riser height within any flight of stairs cannot exceed the smallest by more than 3/8 inch. These dimensions are designed to ensure a safe, comfortable stride for occupants.
MHIC Building Codes and Standards 4
Under the International Energy Conservation Code (IECC) as adopted in Maryland, what is the minimum insulation R-value required for an attic in Climate Zone 4 (where most of Maryland falls)?