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Dealing with Truss Heel Heights
Dealing with Truss Heel Heights
Heel Height: The vertical distance from the top plate to the underside of the roof sheathing measured at the outside wall.
Heel Height = Plumb Cut of Top Chord + Butt Cut of Bottom Chord
Usually Butt cut of Bottom Chord is 1/4".
- Heel Height constitutes to be one of the important parameter of Truss Design.
Standard Heel Height: The standard heel height is one which we consider with 2x4 Top Chord. Using 2x4 heels can keep the over all price competitive. However if the house have volume ceiling or Top Chord of the truss needs to be made 2x6 in case of long span then Heel Height has to be changed from 2x4 to 2x6.
Some plants prefer to keep 2x6 as their standard heel height in lieu of 2x4
Using 2x6 as standard heel has following advantages:
It has better insulation
Easier to design trusses with volume ceiling
On design need basis, we can increase the top chord to 2x6.
Note: If we use 2x6 as Standard heel height on a particular job, then it may happen that for a small area like Front or Rear porch, whose fascia does not match with entire house then 2x4 Heel Height for that porch area can be considered. As these areas will have small trusses and would not require any insulation.
Energy Heel Height: This is basically a raised heel to accommodate the depth of insulation. The depth of insulation depends on the ceiling R-Value requirements and type of insulation used. Typical fiberglass batt R-30 insulation is approximately 9 – 10 inches thick (See picture below), So for such case the minimum heel height needs to be 9". The truss designer needs to get the Energy Heel Height confirmed before proceeding to layout. You can find the details of Depth of insulation based on type of insulation and R value from SBCA research report .
Specified Heel Height: Heel heights are sometimes specified on Architectural and Structural drawings . Truss Designer needs to follow the specific heel height for that particular job. It may happen, in Architectural drawings "Raised Heel Heights" are shown but dimension is not called out in prints. In such case, get the heel height confirmed from the authorized person before starting layout.
Below is the general "Heel Height Chart" provided for reference
Below is the general "Heel Height Chart" provided for reference
You can calculate the Standard Heel Height using the spreadsheet . You just need to input "Top Chord" Lumber size and "Pitch" in Green cell shown in spreadsheet.
You can calculate the Standard Heel Height using the spreadsheet . You just need to input "Top Chord" Lumber size and "Pitch" in Green cell shown in spreadsheet.
Click download to get spreadsheet.
Click download to get spreadsheet.
Note: Truss Heel Heights are very important, It is recommended to get the Heel Height verified from the authorized person of your organization before starting the truss layout .
The next topic we would be covering is Dimensions
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