Attachment_2_-_Structural_Assessment.pdf

Architectural/Engineering Services

Structural Assessment, McMaster Long Barn- NOC Investigation McMaster Long Barn (Historic Structure) Helena, MT

Bureau of Land Management Western Montana District Office/Butte Field Office McMaster Trust Site Winston, MT 59601

28 May 2025

US Department of the Interior Bureau of Land Management National Operations Center Branch of Architecture & Engineering (OC-670)

18 June 2025

SUMMARY: Structural Assessment, McMaster Long Barn

Summary-

a. May 2025, Civil Engineer, Grady Anderson, requests structural engineering assistance from the NOC to investigate observed visual structural distress in a timber framed storage barn at the McMaster Trust Site near Helena, Montana.

b. Building was completed circa 1910-1920. The desire is to assess the structural stability of the barn due to building “listing” (leaning) to one direction. Observable deflection of the building is seen from both the interior and exterior. Members are significantly deflected and, in some cases, have failed.

c. Building is a timber framed structure with round timber columns and rough-cut lumber framing and bracing. Siding is 1x12 type planking with batten planks sealing the primary siding joints. The roof framing is 2x4 rafters @ 24” on center and sheathed with 1x planking. Atop the planking is the original shake shingle type roofing and all topped with a galvanized steel corrugated sheet steel. Approximately half of the primary columns are seated in concrete footings whereas the others are simply embedded into the soil. Lateral bracing consists of chevron type, inverted “V” bracing at the exterior walls, longitudinal knee bracing at columns at intermediate (mid) column lines, “X” type plank bracing at the ridge column line and transverse plank type bracing. The building footprint is approximately 48’ (transverse) x 98’ (longitudinal). Two vent structures (cupolas) were part of the original structure although one cupola was recently removed due to structural instability.

d. 28 May 2025, NOC Civil (Structural) Engineer visited the building and conducted a visual inspection of the distress. Interior, exterior and roof framing were inspected.

Personnel attending inspection-

i. Rich Zaragoza, NOC, Structural Engineer, BLM

ii. Grady Anderson, Civil Engineer, Western Montana District, BLM

iii. Sean Clancy, Civil Engineer, Western Montana District, BLM

iv. Chris Pettyjohn, Archaeologist, Butte Field Office, BLM

e. Significant Findings-

• North half of the barn is listing (leaning) from the north to the south

• Bracing members (transverse) have failed due to overstress in bending

• Roof framing members (rafters) appear to be permanently deflected (deformed)

• Exterior north wall severely drifted to the south due to interior lateral loading

• Interior columns north of ridge column line deflected ~2” from absolute vertical

• Building is structurally compromised. Needs redress to prevent collapse

Note the vertical listing (leaning) grade to roof (red line is vertical/plumb for reference)

DETAILED FINDINGS: Structural Assessment, McMaster Long Barn

NOTE: To assist in deciphering described locations/descriptions in the structure, it is recommended to coordinate the drawings in Appendix A, “Analysis Drawings”, with the following narrative.

1. Observations, Exterior-

i. Exterior, North- the entire north exterior wall of the building was observed as listing (leaning) from north to south. The concrete stem wall at the foot of the north exterior wall is deteriorating, severely spalling, and in some cases, has completely degraded to rubble. The north roof is noticeably deflected (sagging). The northeast timber column appears to have been severed at its base and is now embedded in a barrel filled with concrete at grade. See Photos 1-5.

Photo 1: North Face, Exterior (Overall)

Photo 2: North Wall (Looking West, Taken from Northeast Corner)

Note the visible deflection (sagging) in the roof, this area.

Note the obliterated concrete stem wall with remaining reinforcing steel.

Photo 3: North Concrete Stem Wall @ Base of Exterior Wall

Photo 4: Northeast Corner (Note Timber Column Embedded into Steel Bucket)

Photo 5: North Roof Deflection

Note differing opening heights

Note missing planks and differing siding

Note slight bulge in building roof line

ii. Exterior, East- a few siding planks are missing and the siding at the north side of the building is different than the remaining siding. The siding is also deflected at the north half. There is a small “bulge” at the mid-column line, south, roof line. Openings have different header elevations. A 4x4 dimensional lumber column was placed at the southeast corner to replace the original round timber column. See Photos 6 and 7.

Photo 6: East Building Face

Photo 7: Siding is Deflected Outward (North Side, East Face)

Note minor deflections @ eave

iii. Exterior, South- The roof appears to be intact with some minor deflection at the eave.

There is a door opening towards the west end of the building but appeared to be permanently disabled. Vertical lap wood lap siding appears weathered, but largely undamaged. See Photos 8 and 9.

Photo 8: South Face, Overall

Photo 9: South Face

iv. Exterior, West- some missing/deteriorated siding panels were observed. The horizontal splice batten plank is dislodged from the siding. The panel siding is aged but essentially intact. See Photos 10 & 11.

Photo 10: West Face, Overall

Photo 11: Horizontal Batten Dislodged from the Siding-West Face

v. Exterior, Vents (Cupolas)- originally, there were 2 ea. air vents (cupolas) at the ridge of the roof, one at the east and one at the west. In fall 2024, the west cupola was removed due to concerns of instability and/or collapse. The removed structure remains inside the barn. Currently the east cupola is listing (leaning) to the north and racked to the east.

The cupola appears to be unstable. See Photos 12-14.

Photo 12: Remnants of West Cupola

Note deteriorated /missing siding panel.

Photo 13: East Cupola (Racked to the East)

Photo 14: East Cupola (Listing/Leaning to the North)

2. Observations, Interior-

i. Roof Framing- rafters (2x4) on the north half of the barn are noticeably deflected in the area shown in Photo 5. All the rafters appear to be in good condition, but the north rafters may be unserviceable due to possible permanent deflected shapes. The roof planking shows evidence of water infiltration throughout. Ridge beam and mid column support beams appear to be intact. Exterior load bearing wall top plates appear to be intact.

North walls are deflected as described in Section 1a of this report. See Photos 15 & 16.

Photo 15: Roof Framing North Half of Roof

Photo 16: Ridge of Roof (Note Evidence of Water Infiltration-Discoloration)

ii. Timber Columns- Mid-column line, north, columns (1st 4 ea. columns from the east) are listing to the south approximately 1-1/2” to 2”. The ridge line columns (1st 4 ea. from the east) are listing approximately 1” to 1-1/2” to the south. No listing of the mid-column line, south was observed. Some of the timber columns throughout the barn are embedded in concrete footings at their base. The columns appear to be embedded into concrete or into the soil approximately 2’-4’. All the timber columns at the exterior walls appear to be embedded in soil without concrete footings, but only stem wall concrete (as described in Section 1a) superficially surrounding the columns. All timber columns appear to be structurally intact, e.g., no visible insect damage, rot, deterioration, etc., as evidenced by sounding with a hammer. See Photos 17-20.

Deflected rafters

Mid column beam

Red line is plumb line for reference

Photo 17: Mid-Column Line, North (Note Listing of Column from Plumb)

Photo 18: Ridge Column Line (Note Listing of Column from Plumb)

Note lack of concrete footing

Red line is plumb line for reference

Note lack of concrete footing

Photo 19: Mid-Column Line, South (Note Relatively Vertical Orientation)

Photo 20: Exterior Wall Timber Column (Typical)

iii. Interior, Lateral Bracing (Longitudinal)- the longitudinal (along the long dimension of the building) bracing at the mid-column lines (north and south) consists of knee type bracing spanning from the timber column to the roof framing beam. The knee bracing is in good condition and appears to be performing well as lateral bracing. The bracing at the exterior walls (inverted “V”) also appears to be in good condition and performing well providing lateral resistance in the longitudinal direction. The ridge line column line plank “X” bracing appears to be in good condition but is overstressed in bending in a few bays. See Photos 21-23.

Note concrete footing

Chevron bracing

Note deformation due to overstress in bending

Photo 21: Mid-Column Longitudinal Knee Bracing (Typical)

Photo 22: Exterior Wall Chevron (Inverted “V”) Longitudinal Bracing (Typical)

Photo 23: Ridge Column Line “X” Plank Bracing (Typical)

Knee bracing

New member installed by BLM

Note deformation of original member due to overstress in bending

Note storage of lumber/debris behind columns

iv. Interior, Lateral Bracing (Transverse)- the transverse (across the minor dimension of the building) consists of horizontal plank bracing spanning from the mid-column lines to the ridge column line. The plank members appear to be undamaged but is severely deformed in some bays and outright failed in other bays. In a few bays a new horizontal member of increased cross-sectional area was installed by BLM Field staff due to the observed deformation of the original members. See Photo 24.

Photo 24: Transverse Bracing (Typical)

3. Probable Causes for Structural Distress-

i. Deflected Exterior North Wall/Mid-Column Line, North and Ridge Column Line-

There is significant lateral loading in the north-south direction to the north mid-columns caused by storage of lumber and other debris in the northeast corner of the building in the first two bays (See Photo 25).

Photo 25: Northeast Corner of Barn

The storage of this lumber and debris is significant and appears to be collected over time.

Additionally, as the barn shows evidence of water infiltration, the debris likely absorbs moisture causing swelling of the lumber adding additional lateral load to the columns.

This lateral load is transferred to the ridge column line through the horizontal plank bracing as evidenced by deformation of bracing in Photo 24. The lateral load is transferred to the exterior north wall through the diaphragm action of the roof planks and to the exterior wall as depicted in Photo 2. The load is also transferred to the east wall siding as shown in Photo 7.

Another contributing factor is the lack of timber column concrete footings at this area of the barn. Several of the timber columns lack a concrete embedded footing as was installed in other areas of the barn. The constant moisture of the soil within the barn (likely due to livestock waste and water infiltration through the leaking roof) reduces the strength of the soil allowing relatively relaxed movement at the base of the soil embedded timber columns. This condition is also likely contributing to the movement of the north exterior wall timber columns.

ii. Deflected Rafters on North Roof-

The rafters are single span from the exterior wall to the mid-column lines. The lateral load induced on the interior columns is being transferred to the top plate of the exterior wall through diaphragm action which, in turn, induces bending forces into the rafters.

Due to the relatively long span @ ~13’ for a 2”x4” member, constant moisture and bending loads induced by the laterally loaded interior mid-columns, the rafters are deformed. Although not failed, they are likely permanently deformed and unserviceable.

iii. Minor Deflections in Rooflines- The minor deflections (bulges) at the roof lines on the East and South faces (Photos 6 &

9) are likely due to minor movement of the timber columns, perhaps through frost heave or subsidence. Again, as described in Item a above, lack of a concrete footing at these exterior columns could be a contributing factor.

A possible cause could also be differing lengths of the columns. As there is evidence of replacement or modification to structural members over time (e.g., Photo 4), a differing height column could have replaced original columns at the observed deflected areas.

iv. Instability of Cupola- The racking and listing of the cupola are likely caused by the movement of the barn overall. Additionally, the framing connections at the base of the cupola into the superstructure (roof framing) of the barn appear to be aged and/or inadequate. Finally, there are missing/dislodged members (louvers) which reduces the stiffness of the cupola.

As the wind loading at the cupola elevation tends to be greater than that at the wall level, all the contributing factors described here are amplified due to the increased wind loading.

v. Failing and Overstressed Bracing Members- The overall movement of the building is inducing bending forces into the transverse horizontal (transverse) plank bracing members (Photo 24). The overload forces are primarily from the internal lateral loading at the northeast corner storing lumber and debris. Although possibly adequate for wind loading alone, the members appear to be inadequate for the additional lateral load from the northeast corner storage.

The bending deformation of the “X” plank bracing depicted in Photo 23 appears to be induced by wind loading or slight deflection of the timber column. The bracing is located at the far west bay of the barn, this exterior wall accepts the most severe wind loading in the east-west direction.

4. Opinion-

Barring any significant lateral loading event, e.g., seismic activity or extreme wind event, the building appears stable currently. However, the current observed movement, i.e., listing columns, deformed/overstressed bracing, and deflected exterior north wall has jeopardized its sustained structural stability. Should the structure experience significant lateral loading, e.g.

extreme wind or seismic activity, especially in the north-south direction, collapse is a possibility.

It is the opinion of the inspector that the structure needs repair/remediation soon. Although the structure is not routinely occupied by personnel, the structure is “historic” and is desired to remain vertical while maintaining its historic character. The remediation will require significant stabilization and restoration to achieve this desire. See the Recommendations section of this document for recommended remediation measures.

5. Recommendations (in order of importance)-

i. The storage of lumber and other debris at the northeast corner of the barn should be removed or, at the least, removed from loading the columns immediately/as soon as practical. The interior columns are not designed for the current lateral loading imposed by the storage of lumber and debris.

ii. Plumb (make vertical) all deflected columns, to include the north exterior wall. This will require that the columns be released from their supported/supporting roof framing, e.g., bracing, bearing beams, rafters, etc. It is recommended to work this column plumbing operation in phases, e.g., work per bay progression. Upon plumbing each column install a steel reinforced concrete footing surrounding the base of the column.

The concrete footing should be as deep as the current embedment depth of the timber column. The recommendation to install concrete footings applies to ALL columns.

As a part of the plumbing operation of the exterior walls, remove the existing concrete stem walls that are located at the base of the walls (Reference Photo 3). It appears that the stem wall is non-structural that was placed to dissuade water infiltration at the base.

Removal will not compromise the remainder of the superstructure.

Replace the columns at the east corners of the structure with similar members, i.e., round timber columns of similar diameter to the other exterior columns.

iii. Replace the unserviceable roof rafters at the north half of the roof. This will require the removal of the corrugated sheet metal roofing material and the roof planking. Replace any rafter that is permanently deformed greater than L/240 or approximately 5/8” at its midpoint. Reuse members to the maximum extent possible.

iv. Once all columns are plumb and vertical, replace all horizontal (transverse) and “X” type (longitudinal) lateral bracing with minimum 2” thick material. Currently all horizontal and “X” bracing consists of 1” thick material x 8”-10” deep. Replace the existing bracing with members of same depth but @ 2” thick (nominal).

v. Repair and right (plumb/make vertical) the east cupola. Repair would consist of replacing/reframing missing/damaged members and rehabilitating the connections to the primary roof framing. Add lateral bracing, e.g., diagonal members or steel cable tension bracing. Additionally, as time and budget become available, rebuild and reinstall the west cupola. Rebuild to match the east cupola.

vi. Replace all damaged/unserviceable siding panels. Replace with like members to maintain “historic” character of the structure.

vii. Resize those columns where they are causing bulges in the roof line (Reference Photo 9). Resizing may include cutting the tops of columns to match existing elevations of the exterior walls.

viii. Waterproof the roof to dissuade water infiltration. Waterproofing may consist of removing the corrugated metal roof sheets, removing the original shake shingle roof tiles, replacing unserviceable roof planks, and installing a more efficient roofing system that maintains the “historic” character of the structure.

Within the debris and members being stored in the northeast corner of the barn may be useable replacement members for those that are currently installed but are unserviceable. Confer with the Government Contractor’s Officer Representative (COR) to confirm usage of the lumber stored at this location. Additionally, there are possibly useable round timber column sections that could replace deteriorated members in a field to the east of the structure. Again, confer with the COR for the possible use of these members.

6. Possible Rehabilitation Procedure @ Deflected Columns (offered as “information only”)-

i. Working in phases, e.g., one bay at a time, raise the roof framing from the supporting columns, e.g., using mechanical or hydraulic jacks raising the roof bearing beams.

Plumb the columns. (This procedure could be utilized at the north exterior wall.) The timber columns are the primary load bearing element.

ii. Install the concrete footings at the column bases. This will require excavation around the embedded columns, placing a reinforcing steel cage around the column and placing concrete in a circular formed footing. Dimensions of the footing should match those footings that are already installed at other areas of the barn.

iii. Upon appropriate cure time for the concrete footings, lower the roof framing back onto the load bearing columns.

Should there be any questions on the content of this Report, please contact the undersigned.

RICHARD Digitally signed by

RICHARD ZARAGOZA

Date: 2025.06.18 12:52:02 -06'00'

Rich Zaragoza, P.E., C.W.I.

Civil Engineer (Structural) NOC, OC-671, Planning, Design and Construction 505-761-8087 (Office) rzaragoza@blm.gov

ZARAGOZA

mailto:rzaragoza@blm.gov

Appendix A

ANALYIS DRAWINGS

NOC OC-671 (Civil Engineer-Structural)

June 2025

SOUTH

1 2 3 4 5 6 7 8 9

96' - 0"

EXTERIOR COLUMN LINE, 12' - 0" 12' - 0" 12' - 0" 12' - 0" 12' - 0" 12' - 0" 12' - 0" 12' - 0"

A

12' - 0"

MID-COLUMN LINE,

B

EAST 48' - 0" WEST

(BARN OPENINGS) C (BACK OF BARN)

RIDGE COLUMN LINE

D

NORTH

E

EXTERIOR COLUMN LINE,

AREA INSIDE BARN WHERE

DEBRIS AND LUMBER IS RECOMMENDED

TO BE REMOVED AS SOON AS PRACTICAL

1 EXISTING COLUMN PLAN

NTS

NOT FOR CONSTRUCTION

M cM as te r L on g Ba rn

N

A

LY

SI

S

D R

A W

IN

G

S

H el en a, M on ta na

U ni te d

St at es D ep ar tm en t o f t he In te rio r B ur ea u of

L an d M an ag em en t

Da te es cr ip tio n

R ev is io ns cr ip

Checked by:

Checker BLM Job #:

PROJECT #

Date:

June 2025

EXISTING COLUMN

PLAN

S-101 McMaster Long

Barn

6/

/2

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P

WEST CUPOLA

REMOVED BY BLM

FALL 2024

EAST CUPOLA

LISTING/RACKED

WEST

DEFLECTED ROOF AREA

SOUTHEAST COLUMN

NOW 4X4 LUMBER COLUMN

NORTH EXTERIOR WALL

LISTING TO THE SOUTH

EAST

NORTHEAST CORNER COLUMN

EMBEDDED IN CONCRETE BARREL

1 CURRENT EXTERIOR

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St at es D ep ar tm en t o f t he In te rio r B ur ea u of

L an d M an ag em cr ip ev is io ns cr ip

Checker BLM Job #:

PROJECT #

Date:

June 2025

CURRENT EXTERIOR

S-901

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RIDGE ROOF BEAM

TRANSVERSE (HORIZONTAL)

PLANK BRACING, TYPICAL

MID-COLUMN

ROOF BEAM

(TYPICAL)

EXTERIOR WALL

TOP PLATE

(TYPICAL)

LONGITUDINAL SILL PLATE (TYPICAL)

KNEE BRACING,

TYPICAL

CONCRETE FOOTING

(RECOMMENDED ADDITION)

@ ALL TIMBER COLUMNS

LONGITUDINAL

"X" PLANK BRACING,

TYPICAL

EXTERIOR WALL

COLUMN LINE, SOUTH LONGITUDINAL CHEVRON

(INVERTED "V") BRACING,

TYPICAL

RIDGE COLUMN LINE LONGITUDINAL BRACING

TIE (TYPICAL)

COLULMN LINE, NORTH

STRUCTURAL ELEMENT NOMENCLATURE

1 (ROOF AND SIDING NOT SHOWN FOR CLARITY)

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Checker BLM Job #:

PROJECT #

Date:

June 2025

STRUCTURAL

NOMENCLATURE

S-902

/2

:1 8: