How to Measure for a Curb Adapter
Please read the entire page for the best result,
which is a perfect fit, FAST, & the first time!
The RIGHT questions to ask:
- Is the roof top unit that I am replacing installed on the original curb that is roofed into the building?
- If so, is the make and model of the unit present and legible? Please provide this information if available.
- If not, and the unit being replaced is on an adapter curb, is there an identifier plate present on the adapter, and is it legible? Please provide this information if available.
At times, there is no information to be found on the unit, or on an existing adapter curb. In this case, please fill out our field verification form, which can be found here. Please be sure to fill out the entire form, and to identify supply and return. We cannot build your adapter curb without this!
First & Foremost! Please take pictures and send them to us! Pictures really are worth a thousand words, and in this business, can be worth thousands of dollars! There is no such thing as too much documentation.
1. Measure the exact outside dimensions of the original curb that is roofed into the building. (DO NOT MEASURE THE UNIT, UNIT BASE RAIL OR AN ADAPTER CURB IF PRESENT, BUT THE ROOF CURB BELOW. ALSO, DO NOT ADD TO THE DIMENSIONS. OUR ADAPTER CURB DESIGN AUTOMATICALLY DOES THIS FOR YOU.)
2. Measure the supply and return duct openings sizes.
3. Measure duct locating dimensions (distance from outside dimension of roof curb to supply and return duct openings and in between).
4. Is the unit level?
If not, most times we can correct it in the curb adapter. Please indicate which direction(s) the existing curb is sloping, and measurement of slope.
See how to measure for slope HERE.
5. Are there tight clearances? Sometimes there are units installed in areas very close to other units, roof fans, gas piping or electrical, or sometimes a wall or the edge of the roof. Please note any of these conditions.
Here is an example of what your finished existing curb drawing should look like. Please make sure that all of your dimensions, both duct and locating dimensions are filled in and add up to match the outside dimension!
See our Adapter Curb Installation Guide Here
Still stumped? Give us a call or email us! We will be happy to walk you through the process.
DON’T DO THIS!
DO NOT install a curb adapter on top of an existing curb adapter! A curb adapter should ONLY be installed on top of the original factory roof curb, or the curb that is roofed into the building. Any existing curb adapters should be removed from the system. In addition to the structural and weight issues, stacking adapter curbs adds an unnecessary amount of static loss to the duct system, causing your brand new unit to under-perform in most cases.
DO NOT measure the unit or the unit's base rail! In most cases, the roof top unit base rail seats down around the original roof curb, naturally making the unit larger than the roof curb itself. Instead, measure the highest point of the roof curb that is roofed into the building, or right below the unit base rail. Most often there will be a turned out flange or metal flashing strip installed here. Also be sure to measure the supply and return duct openings in the curb BELOW the unit, NOT THE UNIT PAN OPENINGS! Many times the unit openings are smaller than the actual duct below.