R. A. LAWRENCE ENGINEERING LTD.

STRUCTURAL ENGINEERS

61 UNION ST., SAINT JOHN, N. B. E2L 1A2

PHONE: 506-634-8259 Fax: 506-634-8353 email: ra.lawrence@rogers.com

June 30, 2010

School District No. 2

1077 St. George Blvd.

Moncton, N.B.

E1E 4C9

Attention: Mr. Jacques Gervais

RE: Exterior Stone Masonry

Moncton High School

Gentlemen:

As requested, we have undertaken a site review of the exterior stone masonry for

the purpose of identifying the extent of deterioration in the past 6 months.

1. Lintel Beams

As noted in our previous report, distress in the exterior stone masonry is mainly

the result of "corrosion jacking", from the deteriorating lintel beams embedded in the

walls. With exterior cladding constructed as solid masonry, moisture will penetrate the

walls. In the presence of moisture, the embedded lintel beams over the windows have

corroded. With the corroded metal expanding, the stone masonry has been displaced,

causing cracks in the mortar joints. The fractured joints allow moisture to enter the walls;

which increases the rate of deterioration of the steel members.

At the lower levels, horizontal fractures in the mortar joints exist above virtually

all of the windows and to a lesser extent at the upper level. The extent of deterioration is

related to the direction of the prevailing winds during storms; with the South and East

sides showing the most distress.

The rate of deterioration and expansion of the corroding metal is relatively slow.

Over a 6 month time span, the extent of further deterioration was found to be almost

undetectable. The one exception being at a rear entry in the Courtyard, (adjacent to the

Library). The crack width in the mortar joints has increased, with a portion of the mortar

missing. See Photos No. 1 & 2. In the same area, the stone lintel above the window has

been displaced outward. See Photo No. 3. These signs of distress are indications of

ongoing deterioration in the embedded steel members. With the beam concealed, it was

not possible to assess the extent of deterioration. In this area of the Courtyard, the wider

mortar joints near the level of the embedded beams are an indication of past remedial

work to prevent water leaks. It would appear that the beams in the Courtyard are

deteriorating at a faster rate.

2. Caulked Joints

In the past 8 months, District staff have carried out work on the exterior in an

effort to stop water leaks. Above many windows, caulking has been applied to the mortar

joints. The caulking will help prevent moisture entering the building. Unlike mortar, the

caulking will reduce the amount of water entering the fractures, but it will also trap

moisture within the walls. In a solid masonry wall concept, moisture is allowed to

partially penetrate the walls during inclement weather. The water will eventually

gravitate to the lower levels and seep out of the walls. Moisture trapped in the walls will

contribute to the corrosion and deterioration of the beams. Entrapped moisture will result

in a higher degree of saturation of the mortar. When subjected to freeze thaw cycles, the

saturated mortar will deteriorate and displace the masonry stone units. Caulking should

only be used as a last resort to stop water leaks, as it will have a detrimental effect on the

stone masonry.

3. Loose Stones

Around the perimeter of the windows and doorways, a decorative red sandstone

has been employed. For the most part, the stones have weak bedding planes and a high

absorption rate of moisture. In various locations, portions of the stones are missing and

assumed to have fallen to the ground. Under a window in the tower, a small section of

stone has fallen, (since our previous review). See Photo No. 4. At a theatre window along

the side, a portion of sandstone has separated from the main jamb and remains in an

unstable condition. See Photos No. 5 & 6. With the deterioration of the red sandstone, an

annual inspection should be carried out at the start of the school year. At such time, all

loose or separated portions of the stones should be removed.

4. Side Entrance

Over an entrance on the North side, deterioration of the sandstone continues.

Fractures are evident in the bedding planes. See Photos No. 7 & 8. To stabilize the

stonework, we recommend the drilling and installation of epoxy dowels in such a manner

as to intersect the fractures and bedding planes. The dowels are to be fabricated from 1/4"

diameter stainless steel rods.

5. Gymnasium Wall

Constructed in the late 1980's, the exterior walls of the Gymnasium are also

constructed with stones. The stone masonry was installed without control joints. With

shrinkage and thermal movement, near vertical cracks have occurred in the walls. See

Photos No. 9 & 10. Over the years, the fractured joints have been repaired with mortar,

which continues to crack due to thermal expansion and contraction. Repairing the joints

is addressing the symptoms, but not the cause. Corrective action would entail the

introduction of control joints at various intervals in the perimeter walls.

At the Southwest corner of the Gym, thermal forces in the exterior stone occur

from 2 directions. Near the corner, cracking has occurred in the mortar joints of both

walls. Near the top, a stone unit has been displaced outward. See Photos No. 11, 12 & 13.

Remedial action will be required to reset the displaced stones back to their original

position. Constructing vertical control joints near the corners will relieve the thermal

stresses in the walls and stabilize the stone units.

6. Steps at Side Entrance

At the 2 entrances along the North side, stone masonry walls act as rails along the

sides of the steps. Presently, the walls are showing signs of distress. The outer walls have

been displaced outward; up to 1 1/2" laterally. See Photos No. 14 & 15. Cracks exist in

the thickened mortar joints which have been previously repaired. Near the ground level,

some of the stones have deteriorated; due to a water and salt environment combined with

freeze thaw cycles. In the future, consideration should be given to reconstructing the

steps and the displaced masonry.

Summary

With the ongoing corrosion of the lintel beams embedded in the walls, the stone

masonry walls will continue to show signs of distress. With the rate of corrosion being

relatively slow, deterioration in the stone masonry walls was not apparent; the exception

being the West wall of the courtyard, adjacent to the Library. In the future, the rate and

extent of corrosion in the embedded steel members will increase; with the fractures in the

mortar joints allowing more moisture to enter the walls. Under such conditions, both

vertical and lateral displacement of the masonry stones is anticipated along with

additional water leaks within the building. Corrective action will require the removal and

replacement of embedded steel beams over the windows at all 3 levels.

The remaining items noted in this report, including the loose portions of stones,

displacement of exterior stones in the Gym walls, and deterioration in the stone masonry

at the North side entrances are localized items which should be addressed in the very near

future.

If further discussion and/or assistance is required, please contact the undersigned.

Yours truly,

R. A. LAWRENCE ENGINEERING LTD.

Raine Lawrence, P. Eng.

Photo No. 1

Courtyard: Deterioration in the Joints

Photo No. 2

Courtyard: Deterioration in the Joints

Photo No. 3

Displaced Stones

Photo No. 4 Missing Stone

Photo No. 5

Loose Stone

Photo No. 6

Loose Stones