Why Construction Document Understanding Matters

The Architecture, Engineering, and Construction (AEC) industry runs on documents. Drawings, schedules, specifications, and revisions define scope, cost, and risk across the entire project lifecycle. Yet these documents were never designed for machines.

A single construction drawing set can exceed 100 pages and combine vector floor plans, dense schedules, scanned text, symbols, legends, and cross-referenced specifications. Meaning is distributed across pages and formats, not contained in linear text.

Unlocking this information reliably enables critical downstream workflows:

• Quantity takeoffs for estimating and procurement

• Value engineering (VE) to evaluate cost and scope alternatives

• Conversational analysis to query drawings and specifications directly
  
  

Despite recent advances in large language models (LLMs), production-scale construction document understanding remains unsolved.

Understanding construction documents at scale is not a model problem alone — it is a systems problem.

General Approach

The Paladio AEC Agent approaches construction document understanding as a coordinated, agentic workflow rather than a single extraction task. Instead of treating a drawing set as unstructured text or images, the system decomposes documents into semantically meaningful units, reasons about the role each unit plays within the overall set, and applies specialized processing paths accordingly. Multiple agents collaborate to interpret content, validate signals, and reconcile information across pages, allowing the system to construct a consistent, document-level representation from heterogeneous inputs. This design enables robust handling of large, variable drawing sets while maintaining predictable behavior across accuracy, latency, and cost constraints.

Evaluation Scope & Methodology

Evaluating an agentic system for construction document understanding requires balancing accuracy, latency, and cost across different stages of the construction lifecycle. The acceptable trade-offs between these factors vary by use case. During early design and conceptual evaluation, teams often seek directional insight into how design changes affect scope and cost, where single-digit precision in quantities may not be critical. In contrast, during detailed estimating and construction execution, even small errors in product specifications or quantities can propagate into procurement mistakes and downstream risk.

To build confidence that the Paladio AEC Agent can operate reliably across these scenarios, we evaluate performance along three dimensions: extraction quality, end-to-end execution characteristics, and operational predictability. Rather than optimizing for a single metric in isolation, the evaluation focuses on whether the system maintains stable, bounded behavior under real production constraints, including large document sizes, heterogeneous content, and repeated re-runs after revisions.

The Real Constraints: Accuracy, Latency, and Cost

In production AEC workflows, success is defined by three non-negotiable factors:

• Accuracy
  Missed quantities or misclassified schedules propagate downstream into pricing, procurement, and bid risk.

• Latency
  Processing must align with estimating and procurement timelines, including re-runs after drawing revisions.

• Cost predictability
  Per-document inference costs must remain bounded across large project volumes.

Many off-the-shelf LLM pipelines are optimized for flexibility or small-scale tasks, but can exhibit trade-offs when all three constraints are applied simultaneously.

We also compare to some popular off-the-shelf LLMs that do the job fully automatically by simply taking the contents of each LLM page, and extract contents directly or do the take-off directly.

The observations described below reflect internal evaluations conducted on representative construction drawing sets under specific production constraints (page count, document variability, and takeoff completeness requirements).

Results may vary depending on document characteristics, system configurations, prompts, tooling, and model versions. This analysis is not intended as a universal benchmark.

Early Takeaway: Task-Level Performance on a 100-Page Drawing Set

Before diving into detailed metrics, one result consistently surfaced during evaluations:

While generic pipelines may appear faster on isolated subtasks, end-to-end consistency and reconciliation proved to be the primary determinants of production reliability.

For a deeper breakdown across extraction categories, see the measured performance table below.

Benchmarking the Landscape: What We Evaluated

Before developing our AEC Agent, we evaluated multiple model categories and pipeline designs across real construction drawing sets.

Model Categories Evaluated

• Vision-based segmentation models (e.g., SAM)

• Layout-aware parsers (e.g., LayoutParser, Docling)

• General-purpose LLMs accessed via OCR + LLM pipelines

• Hybrid OCR + LLM systems

• Domain-tuned internal models

Test Characteristics

• 50–150 page drawing sets

• Mixed plan-heavy and schedule-heavy documents

• High-density tabular schedules

• Real-world noise (inconsistent formatting, abbreviations, missing legends)

All evaluations were conducted using publicly available models and standard tooling configurations available at the time of testing.

Are Vision-Only and Layout-Only Approaches Enough?

Short answer: they help, but they are not sufficient for production-grade AEC takeoffs.

Key Findings

• Vision-only models reliably identify where content exists, but struggle to determine what that content represents.

• Layout-aware parsers improve text and table extraction, yet break down when document structure varies or cross-page reasoning is required.

• Both approaches add preprocessing value, but fall short as end-to-end solutions for construction takeoffs at scale.

What We Observed in Practice

Vision-based segmentation models

• Accurately isolate regions such as tables, drawings, and annotations.

• Lack semantic understanding to differentiate schedules from notes or legends.

• Require extensive downstream logic to convert detected regions into construction-ready quantities.

Layout-aware parsers

• Improve separation of text blocks and tables compared to raw OCR.

• Become brittle when layouts shift slightly between pages.

• Do not capture drawing semantics or reconcile information across pages.

In isolation, these approaches perform well on individual pages. In production drawing sets, however, their limitations compound as page count and variability increase.

How Far Do Generic OCR + LLM Pipelines Actually Go?

High-level takeaway: generic OCR + LLM pipelines perform well on small subsets, but struggle to maintain consistency, predictability, and cost control at full document scale.

Key Findings

• Strong semantic reasoning on isolated pages.

• Degrading performance as document size and heterogeneity increase.

• Rising latency and highly variable costs under production workloads.

What Happens at Scale

As drawing sets grow larger and more complex, we consistently observed:

• Context fragmentation caused by text-based chunking.

• Inconsistent outputs across pages processed independently.

• Table truncation driven by token limits.

• Increased latency from parallel LLM calls.

• Cost variability that scaled with retries and document size.

Most importantly, schedules, plans, and notes were typically processed using identical logic, leading to ambiguity during extraction and aggregation.

These pipelines can be effective for targeted tasks, but without document-level structure and routing, they struggle to produce reliable, construction-ready takeoffs.

Why Generic Chunking Pipelines Break Down at Scale

Generic OCR + LLM pipelines struggle at scale due to a few core structural issues:

• Layout is lost early
  Text chunking discards visual cues needed to interpret tables, symbols, and drawings.

• Page intent is ignored
  Schedules, plans, and notes are processed uniformly despite serving different roles.

• No cross-page reconciliation
  Chunks are handled in isolation, so related information is never aligned.

• Retries compound cost and latency
  Partial failures trigger retries that scale poorly with document size.

These limitations make generic chunking pipelines difficult to scale reliably for full construction takeoffs without system-level changes.

From PDF to Takeoff: System-Level Architecture

The AEC Agent is designed around a single objective:

Input: Construction PDF
Output: Construction-ready quantity takeoff

To achieve this reliably, the system performs:

• Intent-aware parsing
  Pages are analyzed and routed based on relevance to takeoff workflows.

• Structured extraction
  Tables, annotations, and symbols are processed using layout-preserving logic.

• Document-level reconciliation
  Quantities are aggregated and validated across the full drawing set.

• Isolated failure handling
  Errors are contained at the page level rather than cascading across the document.

These mechanisms are internal implementation details; their significance lies in their effect on accuracy, latency predictability, and cost control.

Measured Performance (Internal Evaluations)

The table below summarizes illustrative ranges observed during internal evaluations on full drawing sets. Values are approximate and context-dependent.

Results reflect internal evaluations under specific constraints and configurations.

Why End-to-End Latency Matters in Construction

In real construction workflows, takeoffs sit on the critical path between drawings and bids. Drawing sets frequently undergo revisions, requiring re-runs under time pressure. In this environment, end-to-end document latency matters more than isolated model inference speed.

Developer Perspective: Reliability at Scale

From a systems standpoint, production pipelines must be:

• Predictable in runtime
  Estimating and procurement workflows depend on consistent turnaround times, not best-case inference speed.

• Stable under document variability
  Pipelines must handle changing layouts, mixed content types, and incomplete legends without cascading failures.

• Cost-controlled across volume
  Latency spikes often correlate with retries, token overuse, and parallel calls, driving up operational cost.

Operational overhead from retries, token variability, and silent failures can quickly outweigh apparent speed gains from simpler pipelines.

Contractor Perspective: Time-to-Takeoff

From a contractor’s perspective, latency directly impacts competitiveness:

• Delayed quantities slow pricing and subcontractor outreach

• Rework compounds time loss across bid cycles

• Reduced responsiveness limits the ability to adjust to late or revised drawings

In this context, reliable end-to-end turnaround is more valuable than fast but inconsistent per-page processing.

See the AEC Agent in Action

Construction document understanding only matters if it works under real production constraints. The Paladio AEC Agent is designed to process full drawing sets, generate construction-ready outputs, and operate predictably at scale.

At Paladio, our agentic AI team is focused on extending human capability in building the world—by enabling fast, accurate understanding of complex construction documents.