What Happens When the Architect Says: "No Columns."?!
Well, after we all had a good laugh and then verified that the designers at Swatt MiersArchitects weren’t kidding and verified that they and the owner understood the cost implications, we rolled up our sleeves and started engineering!
The developer of this custom home in Burlingame, currently nearing completion, wanted to cantilever the master bedroom some twenty feet over the hillside to maximize the architectural drama and in order to take full advantage of the views.
The structural solution involved mirroring and interconnecting the cantilevering steel framing on both the floor and roof to help control deflection and mitigate vibration concerns.
Hohbach-Lewin provided full civil and structural engineering design services for the development of this very challenging hillside lot. Integrating the civil design with the structural was key to the success of the project; the line between site and building retaining walls definitely blurred.
The building departments of each city has their own unique site development requirements – Hillsborough proved to be no different in this regard. Per Hohbach-Lewin civil engineering Project Manager, Bill Henn, “The requirements were not that onerous – assuming, of course, that you know what those requirements are ahead of time – we were able to draw on our past experience working in the City of Hillsborough to make sure there were no surprises.”
Feel the (Heart) Burn...
Current Code language includes some very vague directives which states: “Where columns are required to have protection to achieve a fire resistance rating, the entire column shall be provided individual encasement by protecting it on all four sides for the full column height…” Clear and simple enough for isolated wood posts acting as columns in the middle of the room; problematic though for a column supporting a beam which is embedded within a wall.
The vast majority of building officials have interpreted posts embedded within walls sheathed in sheetrock to meet this standard. Lately though, in more than one instance, designers have encountered city plan checkers who, despite years of precedent, have decided that wood posts inside walls must now be individually wrapped in order to comply with the code language. The 2018 ICC will clarify this by explicitly stating that this provision does not apply to posts extending between the plates within walls. This should end this argument now and in the future – but if your building official does not find that persuasive, fortunately the ICC Tri-Chapter Uniform Code Committee has approved a policy confirming that the future code language is currently applicable. This policy will be published in mid-July.
Follow this link for a more in depth discussion of this issue authored by Kerry MacDonald, SE.
Relevant 2018 ICC Provision will read as follows:
704.4.1 Light-Frame Construction. Studs, columns, and boundary elements that are integral elements in walls of light-frame construction, and are located entirely between the top and bottom plates or tracks shall be permitted to have required fire-resistance ratings provided by the membrane protection provided for the wall.
Hohbach-Lewin Planned Merger Strengthens Southern California Presence
Hohbach-Lewin’s Southern California presence is now provided by the newly formed Kanda Tso Hohbach Lewin partnership. In early 2016, Hohbach-Lewin purchased a significant minority interest in the South Pasadena based structural engineering firm, Kanda and Tso Associates (established in 1990). This venture is the first step in our anticipated merger planned for 2018.
Kanda Tso Hohbach Lewin is a twelve person firm with full Revit and AutoCAD capabilities. The South Pasadena office includes founding principal, Les Tso, SE and longtime associate, T.J. Wu, SE.
Kanda Tso Hohbach Lewin will combine forces with our Northern California affiliates as needed and as deemed beneficial in order to deliver superior service to our southern California clientele.