B 3.0
Structural modification
Leg, diagonal and foundation reinforcement carried out to a structural engineer’s drawings, so a structure can carry a loading it was not built for.
AGL0–300′
Structures acquire equipment. A tower built in 1998 for one carrier now carries three, plus microwave, plus somebody’s public-safety radio, and every one of those added wind area the original design never saw.
Modification is how a structure catches up with what is already on it, or gets ahead of what is about to be. It always starts with a structural analysis: a qualified engineer models the structure against the proposed configuration and the governing wind loading, and produces drawings for whatever has to be strengthened.
Our work begins where those drawings end. We install the reinforcement member by member, photograph each one, and hand back a package that shows the modification was built as drawn. The one thing we will not do is start before the analysis exists, because installing steel to a guess is the one failure mode in this trade with no recovery.
Nobody climbs to add steel before a structural analysis says what the steel is. This is the one stage in the sequence with no acceptable shortcut, and a contractor who offers to skip it is offering you their liability rather than a saving.
Define these before a proposal
- The analysis
- A structural analysis for the proposed configuration, produced or commissioned before anything is ordered. This is a hold point.
- The drawings
- Engineered modification drawings naming every member, its material, its connection and its torque.
- Existing condition
- What is actually on the structure now, verified rather than taken from a record that may be years out of date.
- Outage windows
- Whether sectors can be taken down, when, and for how long. This usually governs the schedule more than the steel does.
- Close-out format
- How the carrier or owner wants the modification package submitted, agreed before the crew mobilises.
What you receive
Modification close-out package, photo documentation per member
Submitted in the format your QA process expects, agreed at proposal stage rather than discovered at submission. See the close-out package.
B 3.1 The work
What the scope contains
Planning durations for one structure or one site, with the crew type each line assumes. Crew types are priced on the rates page.
| Work | Crew | Typical duration |
|---|---|---|
| Leg reinforcementBolted or welded, per engineered drawings | C4 | 1–3 weeks |
| Diagonal and horizontal reinforcementMember replacement or addition | C4 | 4 days–2 weeks |
| Mount reinforcementSector frame strengthening or replacement | C4 | 2–5 days |
| Foundation modificationWhere the analysis calls for it | GP + subcontract | 2–4 weeks |
| Guy anchor remediationInspection, excavation, repair | GP | 1–2 weeks |
| Post-modification verificationPlumb, tension, as-built check | C2 | 1 day |
Rates are USD, exclude engineering, permitting, materials, crane and specialist equipment hire, travel outside the base market and any applicable tax, and are planning ranges for scoping a project rather than an offer or a quotation. Reviewed September 2026. Durations are per structure or per site and exclude mobilisation, weather days and any engineering or permitting lead time. A figure for your site list comes from a written proposal against a defined scope of work. See the disclaimer.
Questions Structural modification
Questions about this scope
Specific to this scope. The general ones — proposals, insurance, weather, close-out, billing — are on the FAQ page.
Do you produce the structural analysis yourself?
The analysis is produced by a qualified structural engineer. We can carry it in the project and coordinate it, or work to one you already have — many owners have a standing relationship with an engineering firm that knows their portfolio, and that is usually the faster route. Either way, the analysis exists before steel is ordered.
How long does the analysis take?
Two to four weeks is a realistic planning range once the engineer has current structure data and the proposed configuration. It runs longer when the existing condition is uncertain and a mapping visit is needed first, which is common on older structures where the records and the reality have drifted apart.
Can the site stay on air during modification?
Usually, partly. Most modification is carried out around live equipment, and the outages that are genuinely needed are planned into the sequence and agreed in advance. Tell us the outage rules at proposal stage: they frequently govern the schedule more than the steel does, and a programme built without them is a programme that will change.
What is in the modification close-out package?
Photographs of every member installed, torque records, material certifications where required, red-lined drawings showing anything built differently from the issued set and why, a punch list with its closure, and the post-modification plumb and tension record. It is the evidence that the structure is now what the analysis says it is.
B 0.0 The other scopes
The rest of the elevation
- AGL0–300′
Inspection & Maintenance
Scheduled structural and lighting inspection, guy tension and plumb, and the photo-documented report with a punch list that a site owner can act on.
- AGL60–300′
Antenna & Line Systems
Mount steel, antenna and line installation, hoisting, grounding and the sweep and PIM testing that proves the system before the crew leaves.
- AGL0–300′
Tower Construction
New self-support, monopole and guyed structures, erected to an engineered rigging plan and handed over plumb, tensioned and documented.
- AGLGrade
Site Power & HVAC
Standby generators, automatic transfer switches, fuel systems and shelter HVAC — the systems at the base that decide whether the site stays on air.
Send the site list
Telephone with the structures, what has to happen at each one, and the date it has to be finished. We will tell you the crew, the days, what has to be engineered first, and what the close-out package will contain.
Atlantic Tower Services, Inc. · 5301 Pen Ave, Suite 1001, Sanford, FL 32773