Interior Framing Scrimmage
As with most projects, Architects will draw or model interior walls to show the outside of drywall only. This is for clarity’s sake when the documents are printed. This also allows printed sheets to show walls using only two lines and makes dimensioning easier.
During the work on the new Trimble Campus in Westminster, CO, the general contractor, JE Dunn, was able to model the interior framing down to the individual metal studs utilizing Tekla Structures metal stud framing components. The reasons for taking the modeling to this level were two-fold: one for quality control to ensure mechanical, electrical, and plumbing systems were actually within the stud cavity; and two, to be able to layout with the Robotic Total Station where the actual bottom framing track would be installed. By laying out the actual track location, in lieu of just the outside of finished wall, it saved the framing subcontractor from having to chalk finish and offset lines for each side of wall.
Using multiple monitors to show the PDF floor plans with wall type call outs, door schedules, window schedules, wall schedules, and the Tekla Structures model with the Architectural model overlaid, it was easy to cross reference actual opening sizes and wall types while modeling the interior framing. The first floor consisted of approximately 32,000 SF of support spaces including training facilities, demonstration areas, office space, loading docks, storage, fitness area, cafeteria, and reception. Most of the first floor walls were 1-Hour fire rated walls framed in 2-1/2”, 3-5/8” or 6” metal studs, but several areas were or 2-Hour fire rated walls for life-safety exit corridors or storage areas. The Tekla Structures metal stud framing component created each type of wall with correct dimensional offsets for the fire rating and correct king-stud framing around door and window openings. The second through fourth floors consisted of office areas, meeting spaces, and core functions and basically repeated from one floor to the next.
Several issues were found during the modeling of the interior metal stud walls. One issue was that many walls modeled by the Architect with only two lines extruded vertically were drawn with the incorrect widths, and therefore any plan dimensions would be flawed. In addition, when the second, third, and fourth floors were modeled down to the metal stud level and then isolated in plan view, many of the walls that were meant to stack vertically did not match up. This inconsistency from floor to floor could have been due to different detailers drawing different floors or modifications made during the design process that affected one floor but were not transferred to the other floors. Although minor dimensional discrepancies from floor to floor seem harmless, this would have caused issues with the MEP trades trying to run vertical piping from one floor to the next. Another issue that would not have been discovered without modeling of the interior framing were plumbing waste and vent lines that were within the architectural wall lines but not within the actual stud cavity, thereby causing drywall to be bowed or a change to the framing.
This is a common issue on most projects and it requires a wall to be moved or a furring wall built to hide the piping. Modeling of the interior stud walls allowed these issues to be caught before any boots, materials, or equipment even hit the ground.
Here are a few words of caution for anyone new to the modeling of interior metal or wood stud framing. Many times the Architects will have interior details shown as typical call outs. These typical details often are not shown in the standard Architectural model based upon the level of detail the model was created to or required by contract. Many details such as end points of the walls or where they intersect with exterior framing or curtain walls will not be shown exactly. Many specifications will require a certain distance between the door jambs and interior corners of adjacent walls. Many times the Architectural models will not show the jambs and the typical distance off of interior corners to allow for ADA access or finishing of drywall. These issues often don’t get picked up by interior framing crews either, but if the model to the field workflow is to be implemented, the person modeling the interior stud walls will need to reference the entire drawing package and specifications.
As the framing and drywall subcontractor, Phase 2, did not have an internal BIM department or total station layout. So JE Dunn laid out all interior walls at the actual track line by placing points with the Trimble Robotic Total Station (RTS) and Trimble Field Link Tablet at every interior and exterior metal track corner, every door jamb, all openings, every window corner, all column surrounds, MEP chases, and even the curvilinear soffits overhead. It was decided that priority walls would be laid out first for drywall top out prior to critical ductwork and other MEP installations with the remaining walls laid out as time allotted. Once the track lines were chalked, the MEP trades were required to lay out any special openings for duct, piping, or chases before the framing started to ensure there was not wasted time framing the standard 16” on center studs with the MEP trades ripping out studs later during installation. JE Dunn even went down to creating points for the fire extinguisher cabinets to ensure they were framed correctly and the MEP trades did not use up the intended stud cavity. As MEP penetrations and sleeves were QC checked with the RTS and Trimble Field Link prior to concrete pours, almost every sleeve and penetration were within the actual stud cavity upon completion.
JE Dunn also laid out exterior walls for prefabricated panel sections by placing center lines of the panels and offset lines of the grid. With the steel and concrete edges being so closely monitored and controlled, the prefabricated panels went in smoothly and allowed for guaranteed window openings which were also prefabricated and set quickly. As almost every interior wall went to the bottom of the metal deck, a decision was made that the interior walls would not be prefabricated. Checking for pre-and post-pour camber with the Trimble RTS allowed the contractors and subcontractors to adjust their coordinated models prior to any installation occurring. However, with laser scanning and RTS layout, future projects will be able to prefabricate entire wall sections with drywall installed on one side and MEP stubs already in place and be able to roll the walls directly onto the track lines as long as room is made for slip track at the top of wall or they are not taken all the way to the bottom of deck.
Many people on our project did not believe that using the RTS was any faster or more accurate than utilizing the traditional methods of laying out with tape measures off of grid lines. So we decided to host a friendly scrimmage. After laying out all of the interior and exterior walls for floors 1 – 3, we hosted a layout competition on the 4th floor in order to get side by side comparisons and metrics for the utilization of the Trimble RTS.
Caption:Interior wall layout competition coin toss to see which side of the building the traditional layout team got to choose versus the Trimble Robotic Total Station.
Phase 2 had their best crew for interiors walls race JE Dunn using the Trimble RTS. Phase 2 utilized their traditional plans, tape measures, chalk lines, and squares. In order to make sure the competition was fair, the Phase 2 was allowed to pick which half of the building they were going to lay out after winning a coin toss. After the competition was over, JE Dunn’s team had produced 200 points in the time that it took Phase 2 to lay out 100 points; basically JED was able to layout 2/3rd of the building within the same timeframe Phase 2 laid out 1/3rd.
Caption: Images from the layout competition on the Trimble Westminster building. Image on the left shows one-man layout with the Trimble Robotic Total Station and Trimble Field Link. The image on the RFI’s to the Architect for answers.
Phase 2 was also missing numerous dimensions that weren’t on the drawings, they laid out items incorrectly as they referenced the wrong “typical” plan for several rooms, and they did not have any information on windows, soffits, or openings that were already in the model. Typically the Architect can’t provide all the dimensions on the plans as it adds too much clutter. So on a normal project, the framing subcontractor would have to stop production, submit a RFI, and then wait for 1 – 2 weeks per their contract to get the answer back and then the team could check to see if the answer worked. However, with model-based layout, the drawings are created directly from the model, and then we are exporting those points directly to the Trimble RTS and Field Link for layout so there are no missing dimensions. Although JE Dunn did spend time modeling the stud walls in Tekla and then creating the points within the model, Phase 2’s layout crew also spent quite a bit of time going through the drawings and preparing a cheat sheet for dimensions and layout to help increase their productivity.
Caption: Tekla Structures Model showing the Architectural model transparent with metal stud walls and layout points at each stud wall corner, doorframe, and even fire extinguisher cabinet openings.
Caption: Tekla Structures Model showing the Architectural model transparent with metal stud walls and layout points at each stud wall corner, doorframe, and even fire extinguisher cabinet openings.
Caption: Tekla Structures model showing mechanical openings detailed down to the individual metal stud layout.
Caption: Typical floor plan for Trimble’s Westminster building showing how a basic square building can still cause problems for a traditional layout team and how efficient Trimble’s BIM to the Field work flow really is.
We invite you to read through all the case studies from our Westminster Campus building project. Twenty-nine different Trimble building technologies were used on this project and these case studies highlight different efforts including concrete, steel, exterior framing/glazing, and this piece on the interior framing. After reading through these different case studies, consider for yourself if the Trimble Total Station would make sense for your team. We’ve developed an ROI calculator to help you develop the business case. |
