15 Willow Avenue ADU Engineering Report
April 17, 2026
REPORT: GRAVITY DESIGN
ADU Addition At
15 Willow Street,
Salem, MA 01970.
Prepared for: Prepared by:
Anthony Huntley Gelinas Structural Engineering, LLC
15 Willow Street Daniel L. Gelinas, P.E.
Salem, MA. 579A North End Blvd.
Salisbury, MA 01952-1738
Phone: 978.465.643 Danlg@GelinasStructural.com
Scope of Project
Gravity Design of ADU Addition at 15 Willow Street, Salem, MA 01970.
Design Criteria
IRC 2021 as amended by the Massachusetts State Building Code 10th Edition, ASCE 7-16, AISC 360-16,
AISC Allowable Stress Design Manual 15th edition & NDS-18.
Roof Dead Load 15 psf
Roof Live Load 20 psf
Ground snow Pg 50 psf
Wind 119 mph (Ultimate) Exposure C
Table of Contents
Page Item
1) Material & Other Information
1.1) Loading Data
2) Design of Roof Members
3) Design of Second Floor & Deck Member
Job 26051
April 17, 2026
Gelinas Structural Engineering LLC
1) Material & Other Information
I. Structural concrete: -
Structural concrete shall be designed per the ‘Building Code requirements for reinforced concrete
(ACI 318-19).
The concrete used shall have a minimum ultimate compressive strength of 3000 psi (for slabs
exposed to weather) & 4000 psi (for Basement slabs, footing, and walls 28 days.
The concrete exposed to freezing and thawing in a moist condition or deicing chemicals shall have a
minimum ultimate compressive strength of 4500 psi @ 28 days with a maximum water-cement ratio
of 0.45.
All concrete exposed to weather and subject to freezing and thawing during construction shall be air-
entrained, the total air content (percent by volume of concrete) shall not be less than 5% or more than
7%.
II. Structural Steel:
Steel construction shall be in accordance with the latest AISC manual
Structural Steel shall conform to the following ASTM standards:
W Beam & columns : A572/A992-Grade 50 (Fy = 50 Ksi)
Steel Plates, Channels & Angles : A36 (Fy = 36 Ksi)
Structural Pipes & Tubes : A500-Grade B (Fy = 46 Ksi)
Anchor Bolts : F1554 Grade 36 OR A307
High strength bolts :A325
III. Reinforcement: -
The reinforcement of ASTM A615 Grade 60 shall be used in all the concrete structures.
E min. = 29,000,000 psi
fy min. = 60,000 psi
fs = 24,000 psi
IV. Lumber: -
1. Spruce Pine-Fir #2 (For Beams & Headers)
E = 1,400,000 psi
Fb min. = 875 psi
Fv min. = 135 psi
Fc min. = 1,150 psi
2. Boise Cascade Versa Lam (For Beams & Headers)
E min. = 2,000,000 psi
Fb min. = 3,100 psi
Fv min. = 285 psi
3. Spruce Pine-Fir Stud Grade (For Posts)
E min. = 1,200,000 psi
Fb min. = 675 psi
Fc min. = 725 psi
Ft min. = 350 psi
Gelinas Structural Engineering LLC
4. Southern Pine #2 Dense (For P.T. members)
E min. = 1,600,000 psi
5. Parallam PSL Column (For Post)
E min. = 1,800,000 psi
Fb min. = 2,400 psi
Fc min. = 2,500 psi
Ft min. = 1,995 psi
V. Soil Data
Soil Bearing: -
In the absence of a soil report, the footings shall be designed for 3000 psf min. soil bearing capacity
as per IRC 2021 (Gravel/ Sandy Soil).
Gelinas Structural Engineering LLC
1.1) Loading Data
A) Loading & Design Data
Gravity Loads:
I. Sloped Roof Loads
Roof Live Load = 20 psf
Sloped Roof Snow Load = 35 psf
Snow load is governing over Roof Live load, so Snow Load is taken into consideration.
Roof Dead Load = 15 psf
Total Roof Load = 50 psf
Balanced Snow Load = 39 psf
Surcharge Load (pd) = 36 psf
Snow Drift = Balanced Snow Load + Surcharge Load (pd) /2
= 39 + 36 /2
Snow Drift = 57 psf
II. Ceiling Loads
Ceiling Live Load = 40 psf
Ceiling Dead Load = 10 psf
Total Ceiling Load = 50 psf
III. Deck Loads
Snow Drift = 57 psf
Deck Dead Load = 10 psf
Total Deck Load = 67 psf
IV. Floor Loads
Floor Live Load = 40 psf
Floor Dead Load = 10 psf
Total Floor Load = 50 psf
V. Wall loads
Exterior wall = 15 psf
Interior wall = 10 psf
B) Deflection Criteria
For Roof without Plaster Ceiling or Inhabitable Attic Below
Live Load Deflection = L/240
Total Load Deflection = L/180
For Roof with Plaster Ceiling or Habitable Attic Below & Floor
Live Load Deflection = L/360
Total Load Deflection = L/240
For Floor & Deck members (for 2x_ members)
Live Load Deflection = L/360
Total Load Deflection = L/240
For Floor I-Joist
Live Load Deflection = L/480
Total Load Deflection = L/360