CRC Materials & Equipment Knowledge 2

Question 1

What is the minimum compressive strength of concrete typically specified for residential foundations in most US building codes?

Accepted Answer

2,500 psi

Answer

Residential foundation concrete is typically specified at a minimum of 2,500 psi compressive strength per most US building codes.

Question 2

Which type of lumber grade stamp marking indicates the moisture content of the wood at the time of surfacing?

Accepted Answer

KD-19

Answer

KD-19 stamped on lumber means it was kiln-dried to a maximum moisture content of 19% at the time of surfacing.

Question 3

What is the standard width of a residential interior door rough opening when the door unit is 32 inches wide?

Accepted Answer

34 inches

Answer

A 32-inch door typically requires a 34-inch rough opening to allow for the frame, shimming, and installation clearance.

Question 4

Which insulation material has the highest R-value per inch of thickness?

Accepted Answer

Closed-cell spray foam

Answer

Closed-cell spray polyurethane foam provides approximately R-6 to R-7 per inch, the highest of common residential insulation materials.

Question 5

What does the term 'vapor retarder' Class I refer to in residential construction?

Accepted Answer

A material with a perm rating of 0.1 or less

Answer

Class I vapor retarders have a perm rating of 0.1 or less, making them the most effective at resisting moisture vapor transmission.

(CRC) Certified Residential Contractor Practice Test