Horizons

Trex Horizons Installation Guide

AI Reference Edition | Source PDF: 1943f913-c24a-4df6-a73f-07aa917289ca.pdf | Generated 2026-02-20

This Word document is designed for training and answering helpdesk questions. All page numbers below refer to the original PDF listed above.

How to answer with page references

When answering installation questions, give the steps first, then add a short reference line that points the customer to the exact page (and figure) in the original PDF.

Recommended reference line format:

Reference: Trex Horizons Installation Guide - page X (Fig. Y) - short description of the drawing/diagram.

Example:

Reference: Trex Horizons Installation Guide - page 6 (Fig. 2) - hole diameter and depth diagram.

Tip: If the customer mentions a measurement, always quote the number exactly as shown in the PDF and include the page (and figure) reference.

Quick index for common questions

Use this table to jump to the best page for the question you're answering.

Bot-ready answer library (Q&A with page references)

Use the Q&A blocks below as copy/paste answers. Each answer includes a clear page reference so the customer can open the PDF and see the exact drawing/diagram you used.

Standard answer format: steps first, then a one-line Reference, then a one-line visual callout.

If the customer did not specify the fence height or whether the yard is level or sloped, ask those first.

Q: How do I plan my run and calculate sections for Horizons?

Answer:

·        Measure each run and convert feet to inches (ft x 12).

·        Divide by the Horizons section spacing used in the guide and round up any remainder.

·        Do not exceed the maximum on-center spacing called out for Horizons.

Reference: Trex Horizons Installation Guide - page 2 - Planning notes; includes post spacing and run layout guidance.

Bot line: "In page 2 you can reference the drawing showing: Planning notes; includes post spacing and run layout guidance."

Reference: Trex Horizons Installation Guide - page 6 (Fig.1-1A) - Layout drawings showing string line, post marks, and an example run divided into sections.

Bot line: "In page 6 (Fig.1-1A) you can reference the drawing showing: Layout drawings showing string line, post marks, and an example run divided into sections."

Q: What opening size should I leave for a Horizons gate?

Answer:

·        Use the recommended gate opening sizes listed in the tools/materials and gate openings page.

·        Measure opening width at both top and bottom before setting posts.

·        Set gate posts plumb and square before concrete cures.

Reference: Trex Horizons Installation Guide - page 3 - Materials list; shows recommended gate openings for available gates.

Bot line: "In page 3 you can reference the drawing showing: Materials list; shows recommended gate openings for available gates."

Q: What are the parts called (component overview) so I know what I’m looking at?

Answer:

·        Use the component overview page to match part names to the drawings.

·        Confirm whether you are referencing back rails vs front rails before fastening.

·        If a step mentions a part name, match it to the labeled diagram first.

Reference: Trex Horizons Installation Guide - page 4 - Labeled drawing of parts/components and their placement.

Bot line: "In page 4 you can reference the drawing showing: Labeled drawing of parts/components and their placement."

Q: Stepped vs follow-grade: which method should I use on a slope?

Answer:

·        Stepped: fence sections stay level and step down the slope.

·        Follow-grade: fence follows the slope; you must use transition guidance and downhill bracket placement notes.

·        Use the guide drawings to choose the method that matches your yard and desired look.

Reference: Trex Horizons Installation Guide - page 5 - Drawings comparing stepped method and slope-following method.

Bot line: "In page 5 you can reference the drawing showing: Drawings comparing stepped method and slope-following method."

Q: How do I stake the line and mark post centers?

Answer:

·        Stake ends/corners and run a taut string line.

·        Mark post centers at the spacing shown for Horizons.

·        Double-check your last bay before digging so rails fit without forcing.

Reference: Trex Horizons Installation Guide - page 6 (Fig.1-1A) - Layout drawings showing string line, post marks, and an example run divided into sections.

Bot line: "In page 6 (Fig.1-1A) you can reference the drawing showing: Layout drawings showing string line, post marks, and an example run divided into sections."

Q: How deep/wide should post holes be (typical example) for Horizons?

Answer:

·        Use the hole diameter/depth example shown as your baseline.

·        Adjust for frost line, soil, and local code requirements.

·        Keep holes centered on your marks and posts plumb.

Reference: Trex Horizons Installation Guide - page 6 (Fig.2) - Diagram showing hole diameter/depth and notes for local conditions.

Bot line: "In page 6 (Fig.2) you can reference the drawing showing: Diagram showing hole diameter/depth and notes for local conditions."

Q: How do I set posts on level ground?

Answer:

·        Set posts to the height and plumb reference shown in the level-ground drawing.

·        Keep posts aligned to the string line while concrete sets.

·        Re-check plumb before the mix cures.

Reference: Trex Horizons Installation Guide - page 7 (Fig.3) - Drawing showing how to set posts plumb and at correct height on level ground.

Bot line: "In page 7 (Fig.3) you can reference the drawing showing: Drawing showing how to set posts plumb and at correct height on level ground."

Q: How do I set posts on slopes and handle transition posts?

Answer:

·        Use the slope/transition drawings to set the correct post heights.

·        Place transition posts where the grade changes so rails land cleanly.

·        Confirm both plumb and height before concrete cures.

Reference: Trex Horizons Installation Guide - page 8 (Fig.4-5) - Drawings showing transition posts and setting posts on slopes.

Bot line: "In page 8 (Fig.4-5) you can reference the drawing showing: Drawings showing transition posts and setting posts on slopes."

Q: How do I place brackets on a downhill run and where do I cut rails?

Answer:

·        Follow the downhill bracket placement diagram for follow-grade runs.

·        Mark and cut rails only after confirming bracket locations.

·        Dry-fit rails before final fastening.

Reference: Trex Horizons Installation Guide - page 9 (Fig.6-7) - Drawings showing bracket placement when following grade and where to cut rails.

Bot line: "In page 9 (Fig.6-7) you can reference the drawing showing: Drawings showing bracket placement when following grade and where to cut rails."

Q: What’s the sequence: back rails first or horizontal rail first?

Answer:

·        Attach vertical back rails first as shown, then place the horizontal rail.

·        Confirm alignment and level before adding additional fasteners.

·        Do not lock everything down until the section is square.

Reference: Trex Horizons Installation Guide - page 10 (Fig.8-10) - Rail placement drawings (back rails first, then horizontal rail).

Bot line: "In page 10 (Fig.8-10) you can reference the drawing showing: Rail placement drawings (back rails first, then horizontal rail)."

Q: How do I notch and hang the first/top picket?

Answer:

·        Notch the top picket as shown (use the notch detail drawing).

·        Hang/position the first picket per the diagram so the rest align correctly.

·        Confirm your starting picket is plumb before continuing.

Reference: Trex Horizons Installation Guide - page 11 (Fig.11-12) - Drawings showing how to notch and hang the first picket at the top.

Bot line: "In page 11 (Fig.11-12) you can reference the drawing showing: Drawings showing how to notch and hang the first picket at the top."

Q: How do I install the remaining pickets, especially the last picket?

Answer:

·        Install pickets in the order shown so interlocks engage.

·        Use the last-picket technique shown to get the final picket seated.

·        Keep pickets fully seated and aligned before fastening.

Reference: Trex Horizons Installation Guide - page 12 (Fig.13-14) - Drawings showing picket install order and the technique for the final picket.

Bot line: "In page 12 (Fig.13-14) you can reference the drawing showing: Drawings showing picket install order and the technique for the final picket."

Q: When do I attach vertical front rails?

Answer:

·        Attach front rails after pickets are installed, following the front-rail placement diagram.

·        Confirm rail alignment before final fastening.

·        Re-check picket alignment after rail fastening.

Reference: Trex Horizons Installation Guide - page 13 (Fig.15) - Drawing showing front rail placement and fastening.

Bot line: "In page 13 (Fig.15) you can reference the drawing showing: Drawing showing front rail placement and fastening."

Q: How do I secure rails and install post caps?

Answer:

·        Secure rails at the locations shown in the securing diagram.

·        Install post caps per the cap drawing.

·        Confirm caps are fully seated and aligned.

Reference: Trex Horizons Installation Guide - page 14 (Fig.17-18) - Drawings showing securing rails and cap installation.

Bot line: "In page 14 (Fig.17-18) you can reference the drawing showing: Drawings showing securing rails and cap installation."

Q: Do I need the optional mid rail, and where does it go?

Answer:

·        If your fence height/configuration calls for a mid rail, use the optional mid rail drawing.

·        Install it at the placement shown so pickets are supported correctly.

·        Do not guess mid-rail height; follow the diagram.

Reference: Trex Horizons Installation Guide - page 15 (Fig.19) - Drawing showing optional mid rail placement.

Bot line: "In page 15 (Fig.19) you can reference the drawing showing: Drawing showing optional mid rail placement."

Diagram index by page

Use these to quickly reference where a drawing or diagram is shown.

Page 2

·        Sample fence sketch and measurements; section calculation example (divide total inches by 97 and round up).

Page 4

·        Labeled component/parts drawing (helps identify rails, pickets, posts, etc.).

Page 5

·        Stepped vs follow-grade drawings (choose method based on slope).

Page 6

·        Fig. 1 - stake-and-string layout with post locations.

·        Fig. 1A - example of dividing a run into equal sections.

·        Fig. 2 - hole diameter and depth diagram.

Page 7

·        Fig. 3 - setting posts on level ground.

Page 8

·        Fig. 4 - transition posts for slopes.

·        Fig. 5 - setting posts on slopes (follow grade).

Page 9

·        Fig. 6 - downhill bracket placement reference.

·        Fig. 7 - cutting rails on a slope.

Page 10

·        Fig. 8 - attach vertical back rails.

·        Fig. 9 - place horizontal rail.

·        Fig. 10 - horizontal rail positioning details.

Page 11

·        Fig. 11 - notch detail for top picket.

·        Fig. 12 - hanging the first/top picket.

Page 12

·        Fig. 13 - hang remaining pickets.

·        Fig. 14 - last picket technique.

Page 13

·        Fig. 15 - attach vertical front rails.

Page 14

·        Fig. 17 - securing rails.

·        Fig. 18 - post cap installation.

Page 15

·        Fig. 19 - optional mid rail placement.

Key measurements to quote accurately

If the customer asks for exact dimensions, quote from the PDF and include the page reference.

·        Section count example: divide total run length (inches) by 97 and round up.  [Reference: Horizons - p.2]

·        Post hole diameter/depth diagram and any notes for local conditions.  [Reference: Horizons - p.6 (Fig.2)]

·        Stepped vs follow-grade method drawings for installs on slopes.  [Reference: Horizons - p.5]

·        Downhill bracket placement and rail cutting guidance for follow-grade installs.  [Reference: Horizons - p.9 (Fig.6-7)]

·        Optional mid rail placement.  [Reference: Horizons - p.15 (Fig.19)]

·        Gate openings (recommended sizes).  [Reference: Horizons - p.3]

Step-by-step outline

This is a high-level outline. The full details and measurements are in the PDF pages referenced.

Plan the run and post spacing (p.2)

·        Use when customers ask about layout or spacing.

Confirm tools/materials and gate openings (p.3)

·        Best page for 'what do I need?' questions.

Identify parts and orientation (p.4)

·        Use when a customer is unsure what a component is called.

Choose install method (level, slope, or stepped) (p.5)

·        Reference drawings for installing on grades.

Stake and string + mark post centers (p.6 (Fig.1-1A))

·        Shows layout and the example of dividing into sections.

Dig post holes (p.6 (Fig.2))

·        Use for hole size/depth questions.

Set posts (level ground) (p.7 (Fig.3))

·        Plumb posts and set correct heights.

Set posts (slopes and transitions) (p.8 (Fig.4-5))

·        Transition posts and slope alignment.

Downhill bracket placement + rail cuts (p.9 (Fig.6-7))

·        Key page for follow-grade installs.

Install rails (back rails, then horizontal) (p.10 (Fig.8-10))

·        Rail order and positioning.

Install pickets (start/top picket, then remainder) (p.11-12 (Fig.11-14))

·        Includes notch detail and last picket technique.

Install front rails (p.13 (Fig.15))

·        Front rail placement.

Secure rails and add post caps (p.14 (Fig.17-18))

·        Final securing and cap installation.

Optional mid rail (p.15 (Fig.19))

·        Use for taller fence reinforcement.

Bot-ready phrasing examples

You can reuse these patterns so the answer always includes a helpful page reference.

1.      If installing on a slope, decide whether to use the stepped method or the follow-grade method before setting posts. Reference: Trex Horizons Installation Guide - page 5 - stepped vs follow-grade drawings.

2.      Stake and string the fence line and mark post centers; use the example run if you need to divide a long run into sections. Reference: Trex Horizons Installation Guide - page 6 (Fig. 1-1A) - layout drawings.

3.      Dig post holes to the diameter and depth shown in the diagram. Reference: Trex Horizons Installation Guide - page 6 (Fig. 2) - hole size/depth diagram.

4.      For follow-grade installs, use the downhill bracket placement guidance and cut rails as shown. Reference: Trex Horizons Installation Guide - page 9 (Fig. 6-7) - downhill bracket and rail cut drawings.

5.      Use the last-picket technique shown when the final picket is tight. Reference: Trex Horizons Installation Guide - page 12 (Fig. 14) - last picket drawing.