Entity Owned 
For Lease
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Property summary
This exceptional two-story office building, located at 100 Borthwick Avenue in Portsmouth, New Hampshire, offers 47,745 square feet of premium executive office space. Currently, 42,827 square feet is available for lease, with flexible suite sizes ranging from a minimum of 1,748 square feet to a maximum contiguous space of 13,027 square feet. The building, constructed in 1978, sits on an expansive 8-acre lot and is zoned OR - Office Research, providing ample opportunity for a variety of… businesses. The property boasts ample parking for tenants and employees, along with convenient elevator access for ease of movement between the two floors. The building is ideally situated in Portsmouth, NH, with the address being 100 Borthwick Ave, zip code 03801. This location offers excellent accessibility and visibility within Rockingham County. Multiple tenancy options are available, making this property suitable for businesses of various sizes and needs. Interested parties should inquire about the available spaces and lease terms. This is a rare opportunity to secure high-quality office space in a desirable Portsmouth location.
Ownership intelligence
Resolved identity, portfolio, hold profile and investor signals. Included in the full report.
Owner contacts
Skip-traced phones and e-mails of the owner. Included with the full report.
Mortgages
Recorded lenders, amounts and estimated maturities of the owner's loan book — in the full report.
Property tax · 2023
Value estimate
· Sep 2026Realmo valuation models over county records.
Recently sold
No data for this sectionNo cleaned sale $/SF benchmark exists for this use type in this ZIP, submarket or county yet.
Cap rate analysis
Price anchors at 6 / 6.5 / 7% — in the full report.
Zoning insight
Location intelligence
Demand index: how under-served this business type is around this point — modeled from the LocInt grid (area demand vs. what already operates, adjusted by real visit traffic). Higher means stronger unmet demand.
Location
Every figure names its source: public record, benchmark, or modeled. Coverage varies by property — thin data is stated as missing, never invented.
Comparables
6 recorded sales · 15 properties nearbyComparable nearby
Similar Nearby for Sale
Similar in This City for Lease
Instant AI valuation built from comps, income signals, and proprietary benchmarks.A defensible range, not a single guess.
from $99/month
- GBA
- 33,870 SF
- Lot area
- 12.77 ac
- Year built
- 1978
- Stories
- 2
- APN
- PRSM M:0259 B:0015 L:
- Zoning
- OR
- Assessed value · 2023
- $7,196,100
- Annual tax · 2023
- $116,073
- Estimated market rent / SF
- Potential gross income
- Vacancy allowance
- Effective gross income
- Benchmark operating expenses
- Stabilized NOI
- Property tax · 2023
- $116,073
- Selected cap rate
- Financial Building · current use
Cap rate calculated from real income and expense signals, benchmarked against sales of similar assets nearby.
from $99/month
Price sensitivity
The rate is the decision lever; valuation is the consequence.
The recorded zoning designation, what the district officially allows, and the municipal source it comes from.
Zoning designation
Registration is required before the official district profile is shown.
Official district profile
To provide for campus-style development of offices buildings, research and development facilities, and complementary uses
Phones and e-mails of the people behind this property's owner, traced from licensed contact data.
Owner phones and e-mails come with the full report for this property - traced from licensed contact data, with verification and Do-Not-Call flags on every number.
Unlock the evidence behind ownership: portfolio, transactions, debt and signals that help you decide who to contact next.
Registration is required before any owner information is shown.
The mortgage data is behind the paid report: recorded loans of the owner - lender, amount, rate and the estimated maturity - as part of the Ownership Intelligence workspace.
Registration is required before any owner information is shown.
- Ownership
- Owner Contacts
- Full Property Data
- Historical Records
- Value Estimation
- NOI Potential
- Cap Rate Calculation
- Location Insight
- Alternative use
- Local Zoning Insight
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- Full Property Data
- Historical Records
- Value Estimation
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- Alternative use
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