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HomeMy WebLinkAbout430 S Tracy_Structural Peer Review_06.17.2014 234 E Babcock #3  Bozeman, MT 59715  (406) 586-0277  tdhengineering.com June 13, 2014 Mr. George Talbot 430 S Tracy Bozeman, MT 59715 Re: Peer Review of 8/22/07 Structural Assessment Report 430 S Tracy, Bozeman, MT TD&H Job # B14-062 Mr. George Talbot, Per your request, I have performed a Peer Review of a Structural Assessment Report written by Brian May, PE, dated August 22, 2007, for the residential house located at 430 S Tracy, Bozeman, Montana. At the time the initial Structural Assessment Report, Brian May was employed by TD&H Engineering and was a licensed Professional Engineer with the State of Montana. My credentials include an active Professional Engineer (PE) license in good standing with the State of Montana, a Bachelor of Science and Masters of Science Degrees from Montana State University, and eight years of experience in the Structural Engineering field. On June 13, 2014, I performed a site inspection of the residence referenced above to verify the existing condition of the house and to confirm specific items referenced in Mr. May’s Structural Assessment Report. During the site inspection, I was able to confirm that several exterior walls exhibit out-of-plane irregularities and require extensive repair of the brickwork, there is an addition onto the rear of the house that is stick framed and in severe disrepair, the chimney is in sever disrepair, and the floor on the main and upper levels are exhibiting areas of both sag and uplift. In addition to the items noted in Mr. May’s report, it also appeared that the front entry porch is not original based on the type of construction used and that the supporting structure (posts and beams) for the roof appears to be inadequate to support the required City of Bozeman Minimum Snow Load without becoming overstressed. Also, several areas of water damage were observed throughout the house, but no active leaks were noted as I was inside of the house immediately following a rain event; however, this does not confirm nor deny the possibility of active roof leaks. It should be noted that access to the below floor crawlspace to observe the condition of the foundation could not be made during my site inspection due to the access door being fastened shut with wood screws; however, I have no reason to believe that its condition is not as described in Mr. May’s Structural Assessment Report. Mr. Talbot June 13, 2014 Page 2 of 2 In conclusion, my site inspection of the structure and a review of the August 22, 2007 Structural Assessment Report has confirmed that the existing conditions remain consistent with those outlined in the initial report. Furthermore, I am in agreement with all of the items that Mr. May has outlined in his report and concur with his conclusion that the primary issue with the house at 430 S. Tracy is the need for a complete basement and crawl space foundation replacement. As Mr. May mentions, the procedure required to lift the house off its foundation is a large and difficult undertaking, especially for a structure with out-of-plumb exterior brick walls with brittle mortar. Additionally, a significant level of work will be required to upgrade the lateral system of the house to meet current residential design requirement, and it is suspected that there may be structural inadequacies with the floor and front patio gravity framing members. There is also a high probability that due to the instability and brittleness of the existing brick exterior, a potentially unsafe working environment would be created if a foundation replacement was perused. I would also like to reiterate on the fact that Mr. May laid out, that when the compounding effect of all construction issues are analyzed, it becomes apparent that the costs to save and rehabilitate the existing house will be significantly more expensive and labor intensive than if the structure was demolished and rebuilt. I appreciate the opportunity to perform this inspection and provide you with this report. Please review this information and contact me with any questions you may have. Sincerely, Garrett Drake, PE Structural Engineer Attachments: August 22, 2007 Structural Assessment Report by Brian May, PE J:\2014\B14-062 George Talbot - 430 S Tracy Structural Consult\STRUCTURAL\430 S Tracy_Structural Peer Review.docx August 22, 2007 George Talbot Re: 430 S. Tracy Residence 430 S. Tracy Ave. Structural Assessment Bozeman, MT 59715 TD&H Project: B06-069 Dear George, It is our understanding that the current house at 430 S. Tracy will be renovated, or completely removed to facilitate the construction of a new home. A new structure would imitate the existing house that would be removed. To determine the feasibility and cost comparison of the remodel versus demolition approach, per your request I observed & inspected all accessible areas of the basement foundation, crawl space, exterior walls, and building interior. The existing house has a combination of partial brick and stone basement with crawl space foundation, brick exterior walls with stucco shell, ballooned framed stud walls, and wood framed floors. The house was built about 90 years ago, with several interior and exterior changes made to the building since its original construction. After inspecting and analyzing the structure, many issues exist that would require an abundance of reconstruction to improve the structure to a suitable condition. From inspection and analysis, several factors exist that overwhelmingly suggest that a full demolition followed by total reconstruction approach is much more economical, practical, and safer than a renovation. The following report contains specific findings to support this claim. Foundation Based upon the condition and age of the existing stone and brick foundation, in addition to the proposed renovation to the structure, we recommend that the entire existing basement and foundation be removed and replaced. Despite the limited amount of access to inspect the foundation, several issues were discovered that warrant a full basement replacement during the house renovation.  Signs of water damage and heavy efflorescence exist on one surface of the stone wall foundation. Much of the mortar between the individual stones has lost its structural integrity from efflorescence. Large portions of the basement walls are soft and lose material with light mechanical scraping.  The entire load bearing brick wall inside the basement has excessive brick and mortar loss, and is leaning excessively (Photo 1). About half of the brick material is missing from the base of the wall. This entire wall would need to be replaced to safely support any floor framing or bearing walls above.  Several of the existing crawl space support piers were crumbling, unstable and in need of replacement. All the piers observed were in significant disrepair. It can be assumed that additional piers within the crawl space are also in need of replacement (Photo 2 and 3).  Several existing crawl space collector beams are inadequate for the actual span. Several members would need to be reinforced or replaced. To do this effectively, large portions of the main floor would have to be removed for access (Photo 2).  According to residential code for new construction (IRC2006), headroom of a crawl space from bottom of beams and joists to the top of the crawl space fill shall be at least 18 inches. This existing crawl space fails to meet this minimum clearance (Photo 2).  The main floor level is very irregular. There are several excessive high and low points in the floor, with the finished floor elevation varying several inches. This suggests that the existing crawl space framing and pier supports are out-of-alignment and structurally insufficient for the span lengths present.  Due to the poor condition of the existing foundation, it is rather unlikely that the lateral loads transferred to the foundation during a significant seismic event can be safely resisted by the foundation. Large displacements or loss of support above bearing walls would be very probable. Portions of the structure could experience partial collapse.  There are several abandoned holes & shafts in the basement that would require filling (Photo 4).  There is a severe crack in the exterior wall at the southwest corner of the house. The elevation of the main floor drops severely towards this same corner where the severe exterior wall crack is located. This suggests that there is a settlement issue with the existing foundation at the southwest corner of the house. A large area of the flooring and a portion of the existing foundation would have to be removed to repair this problem. Exterior Brickwork We have determined that it is in the best interests of the homeowner to have an entire basement replacement for this existing house. A full renovation of the house structure and interior above grade would be unsafe and impractical if the entire foundation was not removed and replaced. Typically a house underpinning procedure would be the course of action. However, we found the exterior brick of the building to be in such disrepair that it would make any underpinning and temporary jacking procedure very difficult, expensive, and dangerous.  Several exterior walls exhibit a large amount of out-of-plane irregularities including waviness and substantial leaning (Photos 5a & 5b). It is apparent that the brickwork of the walls including the north and south walls are in need of extensive repair. There are areas where the mortar is old and brittle, and has lost its tensile and adhesive properties.  With a foundation replacement required for the house, the superstructure will need to be temporarily lifted and supported. The distressful condition that the exterior brick is in would make this procedure very complicated and expensive. The brick masonry in this poor and irregular condition will most likely not be able to withstand the small amount of movement, racking and force changes associated with an underpinning procedure. It is very possible that large cracks or partial collapses will occur in the masonry during the procedure. To prevent this, an expensive shoring and stabilization system will need to be installed, and it is not guaranteed that it would prevent damage. There is the high possibility that some of the brick would become dislodged during the underpinning and could fall, creating a hazardous condition to workers below.  There are several large cracks in the exterior stucco in strategic areas that suggest there may be hidden areas of substantial brick damage behind. (See Photos 7 through 11).  A more likely scenario is that a full removal of all exterior brick will be necessary, due to the out-of-plumbness and poor mortar condition. If the exterior stud walls are to remain after removing all the brick, there may be large labor costs associated with brick removal while maintaining the integrity of the studs.  The option to remove and rebuild the existing brickwork is not a feasible option. None of the brick can be saved if removed since it is practically impossible to remove stucco from brick. The difficulty to perform a foundation underpinning with brickwork in this condition, combined with the unfeasibility of removing stucco from the existing brick, results in requiring a total brick replacement for the house.  The chimney is in severe disrepair and should either be repaired or removed (Photo 6). Exterior Wall Framing  With its age and its system of balloon-framing, it is doubtful that the existing building has the correct connections and load transfer mechanisms for sufficient shear resistance. Shear loads will not be safely transferred from the roof and floors to the balloon-framed walls without significant improvements.  It is probable that the exterior studs are misaligned and irregular. This could complicate the construction procedure to install shear walls, holddowns, and shear straps. We estimate that about 25% to 50% of the existing studs will need to be removed and replaced. Floor Joist Framing  There are several areas of both excessive sag and uplift in the floor. It was determined that several of the collector beams in the crawl space floor system lack the depth and stiffness to provide a solid floor. Many interior piers are made of unstable piles of stones or mounds of rubble. Some of the spans in the upstairs floor system are too long for the depth and stiffness of the joists. We estimate that 75% of the floor framing system will need substantial reinforcements or complete replacements.  The finished floor and floor finishes will need to be removed during the replacement or reinforcement of the floor framing system. Conclusion The primary issue with the house at 430 S. Tracy is the need for a complete basement and crawl space foundation replacement. This procedure is a large and difficult undertaking, especially for a structure with out-of-plumb exterior brick walls with brittle mortar. A large amount of shoring materials and labor costs will be dedicated to safely and successfully jack the house to allow for the foundation removals and reconstruction. In addition, the floor framing is insufficient in many areas and in need to reinforcements. The balloon-framed nature of the exterior stud system will make it difficult and costly to develop the shear resistance that is required by current residential building codes. When the sum of all construction issues are analyzed, it becomes apparent that the costs to save and rehabilitate the existing house will be much more expensive and labor intensive than if the structure was demolished and rebuilt. Also, the instability and brittleness of the existing brick exterior would create an unsafe working environment during the foundation replacement. I trust that this information meets your immediate needs. Please feel free to contact me should you have any questions. Sincerely, __________________ Brian D. May, PE Structural Engineer Photo 1 -- Load bearing basement wall, with severe brick loss and leaning out-of-plane. This wall is an example of the poor condition of the basement. The entire wall requires replacement. Photo 2 -- Mound of rubble and cobbles serve as an interior bearing point for this crawl space collector beam. Cobbles and soil have been falling off the pile over time. The shallow depth of this major supporting beam attributes to its lack of stiffness, contributing to floor sag at the main level. Photo 3 -- Stack of stone acting as intermediate support at midspan. Edges of stones are adjacent to the edge of supporting soil cut, causing an unstable situation. There is insufficient clearance between the joists and the crawl space fill. Photo 4 -- Example of one of the shafts and wells in the basement floor that requires filling. Photos 5a & 5b -- Waviness of exterior stucco walls. Brickwork out-of-plumb & most likely in disrepair. Photo 6 -- The brick chimney is in severe disrepair. Photo 7 -- Severe crack in stucco at southwest window. This corner area of the house has significant floor sag and suspected foundation settlement. Brickwork is suspected to be in disrepair. Photo 8 -- Severe crack in stucco at northern window. This wall is significantly out-of-plumb. Photos 9a & 9b -- Typical cracks in stucco from window corners to roof overhang. Photo 10 -- Crack in stucco at window. Photo 11 -- Severe crack in stucco between upper and lower level windows.