NCARB PDD Exam - Topic 3 Question 7 Discussion

Actual exam question for NCARB's PDD exam

Question #: 7
Topic #: 3

[All PDD Questions]

Refer to the exhibit.

What is the primary function of the 2 x 4 blocking shown at X in the drawing?

ATransfer the lateral loads from the ceiling joists

BSupport the top of the partition

CBrace the ceiling joists

DTransfer the lateral load to the 1 x 8

Show Suggested Answer

Suggested Answer: C

Comprehensive Detailed Explanation with all NCARB ARE 5.0 Project Development and Documentation (PDD) Study Guide Reference:

In wood frame construction, blocking installed between joists at regular intervals (commonly 48 inches on center) serves primarily to brace and stabilize the joists laterally, preventing twisting and lateral displacement under load.

The 2x4 blocking at point X, placed perpendicular between the ceiling joists, acts as cross bracing.

It resists lateral torsional buckling of the joists and distributes loads evenly.

It also helps maintain alignment during construction and after the finish materials are installed.

The blocking does not support the partition top plate directly (that is the function of the studs beneath), nor does it transfer lateral load to the 1x8. Its main role is structural bracing for the joists.

Supporting Reference:

NCARB ARE 5.0 Review Manual, Project Development and Documentation, Structural Systems chapter

Wood Frame Construction details from International Residential Code (IRC)

Building construction texts such as ''Fundamentals of Building Construction'' by Allen and Iano, which describe blocking used to brace joists.

by Alecia at Nov 21, 2025, 03:53 PM

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Truman

1 day ago

D is interesting, but I lean towards B for the main function.

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Kristin

6 days ago

I feel like B is the safest choice. It’s about stability.

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Tesha

11 days ago

C seems plausible as well. It might brace the joists.

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Marg

17 days ago

But what about A? It could transfer lateral loads too.

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Sanjuana

22 days ago

I agree, B makes sense. It looks like it holds up the wall.

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Solange

27 days ago

I think it's to support the top of the partition.

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Willis

2 months ago

Totally agree with Demetra on this one!

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Paul

2 months ago

Wait, are we sure it's not doing something else?

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Dierdre

2 months ago

Definitely transferring lateral loads from the ceiling joists!

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Shelton

2 months ago

I think it actually supports the top of the partition.

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Demetra

2 months ago

It's for bracing the ceiling joists, right?

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Erasmo

2 months ago

Option D? Really? That's just silly. The 2 x 4 blocking is definitely not for transferring lateral loads to the 1 x 8.

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Veronique

3 months ago

Haha, this question is a real head-scratcher. I'm just going to go with my gut and choose option C.

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Fannie

3 months ago

I agree, the 2 x 4 blocking is clearly for bracing the ceiling joists. Option C is the way to go.

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Argelia

3 months ago

Option C is the correct answer. The 2 x 4 blocking is used to brace the ceiling joists and provide lateral support.

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Tamekia

3 months ago

I feel like the answer is A, transferring lateral loads, but I need to double-check my notes on blocking functions.

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Stephanie

3 months ago

Okay, I've got a strategy here. I'm going to start by visualizing the forces and loads acting on this framing system. That should help me identify the primary purpose of the blocking at point X.

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Thora

3 months ago

The blocking is there to provide lateral support, so I'm thinking it's either option A or D. I'll need to double-check how lateral loads are typically transferred in this type of framing assembly.

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Lorean

4 months ago

I remember a similar question about lateral loads in our practice exam, and I think it might be related to that.

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Billy

4 months ago

I think the blocking is meant to support the top of the partition, but I'm not entirely sure.

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Lorean

4 months ago

I'm a little unsure about this one. The exhibit doesn't give a ton of detail, so I'll need to rely on my construction knowledge to reason through the options. Maybe I can eliminate a couple choices and then make an educated guess.

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Vernice

4 months ago

Hmm, I'm not sure. The blocking could also be used to support the partition. I'll have to think about this one.

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Milly

4 months ago

I’m a bit confused; could it be that the blocking also braces the ceiling joists?

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Cordell

5 months ago

Okay, this looks like a pretty straightforward structural question. I'm going to start by visualizing how the ceiling joists, partition, and 1x8 are all connected and interacting. That should help me figure out the primary function of the blocking.

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Martha

5 months ago

Hmm, I think the key here is understanding the purpose of the 2x4 blocking. I'll need to carefully review the options and think about how the blocking would function in this construction.

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