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Multi-Family Structural certification: Supplying natural gas to individual suites

A Multi-Family Apartment Building

TSSA guidelines state that supplying natural gas to individual suites in new and retrofit buildings over four storeys requires a "structural certification letter". This letter must be signed by an Ontario licensed structural engineer stating that the building is "resistant to progressive collapse".

  1. Structural Certification Requirements for Multi-Family Buildings Supplying Natural Gas to Individual Suites

Sample letters:

  1. Structural Certification Letter for Existing Buildings
  2. Structural Certification Letter for New Buildings

1. Structural Certification Requirements - For multi-family buildings supplying natural gas to individual suites

Natural gas piping can be installed in multi-unit buildings to deliver gas to individual suites.

  • New and retrofit buildings over four storeys require a “structural certification letter” signed by an Ontario licensed structural engineer stating that the building is “resistant to progressive collapse” (see links below for sample letters).

  • Buildings four storeys and under do not require a structural certification letter. Progressive collapse is the chain reaction failure of a substantial portion of a building due to the propagation of a local structural failure (i.e. gas fire). The resulting building failure is totally disproportionate in magnitude to the initial failure.

Which types of buildings are resistant to progressive collapse? Three types of structures have been widely used for high-rise residential buildings:

1.    reinforced concrete slab and wall construction;

2.    reinforced concrete flat slab construction; and

3.    pre-cast concrete slab or steel joist floors supported on masonry walls.

The first two types of structures, if cast-in-place (CIP) and designed and built to Ontario Building Code requirements commencing in 1986, are deemed to be resistant to progressive collapse. The third listed type of construction requires a detailed structural review as outlined in Appendix A of  “Guidelines for the Distribution of Natural Gas in Multi-Family Buildings” (available for purchase from www.tssa.org).

* Note that all building types over four storeys require a structural certification letter, even those deemed to be resistant to progressive collapse.

2. Structural Certification Letter for Existing Buildings

Sample structural certification letter as proposed by local gas utilities for EXISTING buildings exceeding four storeys.

Regional Utility Representative
Sales Office of Appropriate Utility

Re: Existing Multi-Family Building, XYZ Building
     Street Address, City, ON

I, (Name of Engineer), Registered Professional Engineer in the Province of Ontario, structural engineer appointed by the owner to investigate compliance of the Building with the requirements of the TSSA Guidelines for the Distribution of Natural Gas in Multi Family Buildings - Second Edition, dated December 1997 (the “Guidelines”), confirm that I understand the intent of sub-section 1.3 of these Guidelines. Further, I confirm that I am familiar with Appendix A of the Guidelines and have reviewed the design of the Building in accordance with the criteria set out therein.

I have examined copies of the original structural drawings for this building which were approved for construction by the City of XXX on date and which bear the Professional Engineers of Ontario seal of Name of Engineer and such other documents available to me to assist in my understanding of the building’s design. Where important information on the drawings was incomplete, physical investigation was undertaken to confirm, to my satisfaction, that appropriate information was provided for construction.

The building under review is (X) storeys and consists of (XX) units. My examination of the building was undertaken specifically to determine compliance with the specific requirements of the Guidelines with respect to progressive collapse.

The building structure is: (Enter one of the following)

reinforced concrete walls supporting continuous one-way spanning floor slabs in which the minimum areas of reinforcement in each direction, the detailing intended to accommodate continuity moments and the original design live load stated on the drawings comply with the current Ontario Building Code and accordingly resistant to progressive collapse under the Guidelines.

Or

reinforced concrete columns and walls supporting reinforced concrete two-way spanning flat slabs, (with/without) drop panels, which incorporate structural integrity reinforcement complying with the requirements of CSA Standard CAN3-A23.3-M84, “Design of Concrete Structures for Buildings” and accordingly resistant to progressive collapse under the Guidelines.

Or

(Describe the type of construction if it does not conform to one of the two types identified above and give specific reasons why the construction may be considered to be resistant to progressive collapse.)

I acknowledge that (Name of Gas Utility) as relying upon this opinion, to its detriment, with respect to its requirements for compliance with the Guidelines and agrees to indemnify and hold harmless (Name of Gas Utility) from all losses, claims, damages and actions arising, in any way whatsoever, from (Name of  Gas Utility) reliance upon this opinion.

Signature

Engineer’s Name

Engineer’s Stamp

3. Structural Certification Letter for New Buildings

Sample structural certification letter as proposed by local gas utilities for NEW buildings exceeding four storeys.

Regional Utility Representative
Sales Office of Appropriate Utility

Re: Existing Multi-Family Building, XYZ Building
      Street Address
      City, ON

I, (Name of Engineer), Registered Professional Engineer in the Province of Ontario, structural engineer of record for the design of the Building have reviewed the TSSA Guidelines for the Distribution of Natural Gas in Multi Family Buildings - Second Edition, dated December 1997 (the “Guidelines”), and confirm that I understand the intent of sub-section 1.3 of these Guidelines.  Further, I confirm that I am familiar with Appendix A of the Guidelines and have reviewed the design of the Building in accordance with the criteria set out therein.

The building will be (X) storeys and consist of (XX) units.

The type of structure to be constructed is: (Enter one of the following)

reinforced concrete continuous one-way spanning floor slabs supported on reinforced concrete walls, complying with the current Ontario Building Code and accordingly resistant to progressive collapse under the Guidelines.

or

reinforced concrete two way spanning flat slabs (with/without) drop panels, supported on columns and walls of reinforced concrete, incorporating structural integrity reinforcement as required by the current Ontario Building Code, and accordingly, resistant to progressive collapse under the Guidelines.

or

pre-cast concrete slab floors or cast-in-place concrete slab on steel joists supported on masonry walls.  Incorporated into the floors and walls are special structural details designed to provide resistance to progressive collapse in accordance with the structural details set out in Appendix A.

or

(Describe the type of construction if it does not conform to one of the three types identified above and give specific reasons why the construction may be considered to be resistant to progressive collapse.)

Either:  I confirm that the field review of construction will be carried out under my direction.

Or:  The building owner has engaged (Name of Engineer) to undertake the field review of construction, as required by the current Ontario Building Codes.

I acknowledge that (Name of Gas Utility) as relying upon this opinion, to its detriment, with respect to its requirements for compliance with the Guidelines and agrees to indemnify and hold harmless (Name of Gas Utility) from all losses, claims, damages and actions arising, in any way whatsoever, from (Name of Gas Utility) reliance upon this opinion.

Signature

Engineer’s Name

Engineer’s Stamp