Formwork, Shoring & Falsework: Temporary Structures on the PE Construction Exam

Design for support of construction loads is the single largest knowledge area on the PE Civil Construction exam — 10–15 questions by the NCEES specification, more than soil mechanics, more than scheduling, more than safety. It's also the area where field experience helps least: you may have stripped a thousand forms, but the exam asks you to compute the lateral pressure a 16-foot column pour puts on its form at 70°F, and that's an ACI 347R calculation almost nobody runs by hand on site.

The good news is that this domain is built around a small set of published rules. The pressure equations, their applicability limits, the coefficient tables, and the bracing minimums all live in ACI 347R (Guide to Formwork for Concrete) — which NCEES supplies on screen, alongside ACI SP-4 and ASCE 37 — so every number in this post is something you can find, and should practice finding, in the exam-day bundle.

This guide works through the concepts, the four problem types NCEES draws from them, and a full column-and-wall worked problem with the coefficient lookups shown.

Why temporary structures matter on the Construction exam

Beyond the 10–15 directly allocated questions — formwork, falsework and scaffolding, shoring and reshoring, bracing and anchorage, support of excavation, and construction loads on permanent structures — this domain leans on structural mechanics (7–11 more questions), because shores, braces, and form panels are analyzed as beams, columns, and trusses. Together that's potentially a quarter of the exam riding on temporary works. The full map of all eleven knowledge areas is in our complete guide to the PE Civil Construction exam.

One orientation point that saves candidates from over-studying the wrong material: this is not structural design. ACI 318, ASCE 7, and the IBC are not in the Construction bundle. The structural flavor here is statics on temporary systems plus lookup-and-apply rules from ACI 347R, ACI SP-4, and ASCE 37 — our guide to the PE Construction exam's reference standards breaks down which standard answers which question type.

Core concepts you must master

Vertical loads on formwork

Per ACI 347R §4.2.1, dead load is the weight of formwork plus freshly placed concrete and reinforcement; live load covers workers, equipment, runways, and impact. The guide sets design minimums: live load of at least 50 lb/ft² of horizontal projection (75 lb/ft² when motorized carts are used), and a combined dead-plus-live design load of at least 100 lb/ft² (125 lb/ft² with motorized carts). Questions that give you a thin slab and ask for shore loads are testing whether you apply these floors instead of the (smaller) computed load.

Lateral pressure of fresh concrete: the default is hydrostatic

Fresh concrete behaves as a fluid until it stiffens. The baseline design pressure, ACI 347R Eq. (4.2.2.1a(a)), is full fluid head:

where w is the unit weight of the concrete and h is the depth from the top of placement to the point considered. The reduced-pressure equations below are the exception, allowed only when the conditions in Table 4.2.2.1a(a) are met: slump ≤ 7 in. and internal vibration depth ≤ 4 ft. Concrete with slump over 7 in., deep vibration, or self-consolidating concrete (§4.2.2.2) is designed for full hydrostatic head — and concrete pumped from the base of the form gets full head plus a minimum 25% allowance for pump surge pressure (§4.2.2.4).

The column equation

For columns — defined in ACI 347R as vertical elements with no plan dimension exceeding 6.5 ft — at any placement rate, Eq. (4.2.2.1a(b)) gives the maximum design pressure:

with R the placement rate in ft/h and T the concrete temperature in °F. The result has a floor of 600C_w lb/ft² and a ceiling of wh — pressure can never exceed full hydrostatic. Both limits are favorite test points.

The wall equations and the rate breakpoints

For walls (at least one plan dimension over 6.5 ft), the equation depends on wall height and placement rate, per Table 4.2.2.1a(a): walls 14 ft or shorter placed slower than 7 ft/h use the column equation above; walls taller than 14 ft (any rate below 7 ft/h) or any wall placed at 7–15 ft/h use Eq. (4.2.2.1a(c)):

with the same 600C_w minimum and wh maximum. Above 15 ft/h, design for full hydrostatic pressure. The selection logic — element type, height, rate, slump, vibration depth — is exactly the kind of multi-condition lookup the exam builds questions around, and it's all in one table in the on-screen reference.

The two coefficients

The unit weight coefficient C_w (Table 4.2.2.1a(c)): for concrete between 140 and 150 lb/ft³, C_w = 1.0; lighter than 140 lb/ft³, C_w = 0.5[1 + w/145] but not less than 0.80; heavier than 150 lb/ft³, C_w = w/145. The chemistry coefficient C_c (Table 4.2.2.1a(b)) runs from 1.0 for Type I, II, or III cement without retarders, to 1.2 with retarders, up to 1.5 for mixes heavy in slag or fly ash with retarders. "Retarders" includes any set-delaying admixture — a stem that mentions a high-range water-reducing retarder is telling you C_c ≠ 1.0.

Shores, reshores, and the load path

ACI 347R distinguishes shores (members carrying formwork, concrete, and construction loads), reshores (placed snugly under a stripped slab after it has been allowed to deflect and carry its own weight — new loads then distribute to the reshored floors), and backshores (placed before the slab deflects, after forms are removed from a small area only). Multistory questions hinge on the distinction: when a slab is reshored, that slab is already carrying itself, and the reshores only see loads applied afterward. Shoring and reshoring plans, per §4.5, must account for the strength of each supporting floor at the time of loading — concrete maturity questions from the materials domain connect directly here, which is why it pays to study this alongside material quality control and production.

Bracing, anchorage, and accessory safety factors

Braces and shores resist all horizontal loads — wind, cable tensions, inclined supports, dumping of concrete, equipment starts and stops (§4.2.3). For wall and column form bracing, the applied horizontal load must produce effects at least equal to 100 lb per linear foot of wall, applied at the top (§4.2.3.3), with wind per ASCE 37 where it governs. Formwork accessories carry minimum ultimate-strength safety factors from Table 4.4: 2.0 for form ties, 2.0 for form hangers, and 2.0 or 3.0 for form anchors depending on whether they support personnel and impact loads. Given a tie layout and a design pressure, the required ultimate tie capacity is tributary area × pressure × safety factor — a complete exam question in one sentence.

The four problem types you'll see

Type 1: Maximum lateral pressure on a column or wall form

Given element type, dimensions, mix, temperature, and placement rate: select the equation, look up both coefficients, compute, then check the 600C_w floor and wh ceiling. The worked problem below runs both variants in full.

Type 2: Form tie or bracing demand

Type 3: Shore loads by tributary area

A slab of given thickness on shores at given spacing: dead load is slab self-weight plus formwork, live load is at least 50 lb/ft² (75 with carts), the combined minimum is 100 lb/ft² (125 with carts), and the shore load is the governing pressure times the shore's tributary area. Distractors come from skipping the minimums and from using the wrong cart condition.

Type 4: Shoring/reshoring sequence and form removal

Mostly conceptual: which floors carry load when, what a reshore does and doesn't support, and what concrete strength is required before stripping — tied to specified strength, maturity, or contract-document requirements rather than a fixed number. Expect drag-and-drop ordering items here, since sequence questions fit that format naturally.

A multi-concept worked problem

A placement uses normal-weight concrete (w = 145 lb/ft³), Type I cement, no retarding admixtures, slump 5 in., internal vibration depth under 4 ft, placed at T = 70°F. Two elements pour the same day: a 16-ft column form (30 in. × 30 in.) filled at R = 10 ft/h, and an 18-ft wall placed at R = 6 ft/h. Find the design lateral pressure for each form and the minimum top-of-wall bracing force per foot.

Step 1 — Coefficients and applicability

Step 2 — Column form pressure

Step 3 — Wall form pressure

Step 4 — Bracing minimum

Common errors that cost points

Using a reduced-pressure equation when hydrostatic governs the case

Slump over 7 in., internal vibration deeper than 4 ft, placement rate above 15 ft/h, or self-consolidating concrete: each one sends you back to C_CP = wh. The stem mentions slump for a reason. SCC stems are especially common because the "obvious" move — plugging into the column equation — is exactly wrong.

Forgetting the floor and the ceiling

Every reduced-pressure result must be at least 600C_w lb/ft² and no more than wh. A slow, warm pour can compute below 600; a fast, cold pour can compute above full head. NCEES puts the unclamped value among the answer choices both ways.

Misclassifying the element

The 6.5-ft plan dimension defines column vs wall, and the 14-ft height plus the 7 and 15 ft/h rate breakpoints select the wall equation. A 4-ft-thick, 20-ft-long element is a wall no matter how column-like the stem makes it sound.

Dropping the chemistry coefficient

Any retarding admixture — including retarding and high-range water reducers — moves C_c off 1.0, and slag or fly ash blends push it to 1.4–1.5. A 1.5 coefficient changes the answer by 50%; the distractor with C_c = 1.0 is always on the list.

Treating a reshore like a shore

Reshored slabs already carry their own weight; reshores see only subsequently applied loads. Computing a reshore force as if it supported the full slab dead load double-counts the slab and lands on the heaviest distractor. Backshores — installed before the slab deflects — are the configuration that does keep the slab from carrying itself.

Ignoring pump placement

Concrete pumped from the base of the form requires full hydrostatic head plus at least 25% for pump surge (§4.2.2.4) — not the column equation, no matter what the placement rate works out to.

How to study temporary structures effectively

Phase 1: Internalize the selection logic

Before any arithmetic, drill equation selection: ten scenarios, varying element type, height, rate, slump, vibration, admixtures, and placement method, choosing only the governing equation and coefficients for each — the PEwise Construction course's ACI 347R formwork module walks this selection logic case by case in animated lessons. This is where the exam hides most of its difficulty, and it's pure table-reading speed in ACI 347R Chapter 4.

Phase 2: Compute with the limits attached

Work pressure problems end to end, always writing the 600C_w floor and wh ceiling next to the result. Practice until the check is a reflex, not a step you remember.

Phase 3: Statics on the system

Ties, braces, anchors, and shores by tributary area and free-body diagram, with Table 4.4 safety factors applied. Fold in ASCE 37 construction live loads and the §4.2.1 minimums so the vertical-load questions are equally automatic.

Phase 4: Sequence and removal scenarios

Shoring/reshoring/backshoring narratives, form-removal strength requirements, and multistory load distribution — practiced as ordering and concept questions, the way NCEES formats them.

Quick reference: key formulas and values

Item	Expression / value	Source
Hydrostatic (default) pressure	CCP = wh	ACI 347R Eq. (4.2.2.1a(a))
Columns (plan ≤ 6.5 ft), any rate; walls ≤ 14 ft at R < 7 ft/h	CcCw[150 + 9000R/T]	Eq. (4.2.2.1a(b))
Walls > 14 ft at R < 7 ft/h; any wall at R = 7–15 ft/h	CcCw[150 + 43,400/T + 2800R/T]	Eq. (4.2.2.1a(c))
Limits on reduced equations	600Cw ≤ CCP,max ≤ wh	§4.2.2.1a
Formwork live load minimum	50 lb/ft² (75 with carts); D + L ≥ 100 (125 with carts)	§4.2.1
Wall/column bracing minimum	100 lb/ft at top of form	§4.2.3.3
Accessory safety factors	Ties 2.0 · hangers 2.0 · anchors 2.0–3.0	Table 4.4
Pumped from base / SCC	full wh (+ ≥ 25% surge if pumped from base)	§4.2.2.2, §4.2.2.4

Connecting this to your overall Construction exam strategy

Temporary structures is the anchor domain of the Construction exam — start your study plan here, while your energy is highest, because it pairs the largest question count with the steepest reference-navigation curve. It also feeds two neighbors: form-removal and reshoring decisions depend on early-strength and maturity concepts from material quality control, and knowing which of ACI 347R, ACI SP-4, and ASCE 37 answers which question — covered in our guide to the Construction exam's bundled standards — is half the speed battle. For the domain-by-domain weighting that justifies putting this area first, see the PE Civil Construction exam guide.

Final thoughts

Formwork pressure is the signature calculation of the Construction exam — the one domain where NCEES can write quantitative, code-grounded, multi-step problems that no other civil discipline trains for. That's a gift in disguise: the rules are few, published, and supplied on screen, so deliberate practice converts this from the scariest area on the spec to your most reliable block of points. Drill the selection table until choosing the equation takes ten seconds, attach the limits to every computation, and the largest knowledge area on the exam becomes the one you're most certain about walking in.