1. Builder’s Helper MAX
This excellent app will help you calculate roof pitch, rafter lengths, stair lengths, and more. The app has a nice graphical interface that will calculate stair, roof and floor projects.
2. Measure
When you need to take accurate measurements and the only tool you have at hand is your iPhone, the Measureapp is a perfect fit. Tools include a caliper, 25 foot tape measure using the iPhone camera, measuring wheel for distances of 80 feet to a Mile, flexible tape measure and more.
3. Clinometer

This professional tool called Clinometer is the most precise (all you can get with some calculations) slope measurement tool for the iPhone/IPod Touch. It can be used for simple applications like aligning a frame as well as for more sophisticated fields of applications where an arbitrary slope needs to be measured exactly.
4. AutoCAD
here are both free and paid versions of this app. The free version seems to be more popular with 259 ratings as compared to just 3 for the paid version. It allows you to view technical drawings (e.g. drawings from Autocad) so long as they are in DXF textual format. It can be used on the iPhone (OS 3.0 or later), iPad and iPod Touch.
5. Autodesk ForceEffect
Bring engineering to the point of the problem with Autodesk® ForceEffect™, a mobile engineering app for simulating design concepts in the field or in the office. Unlike the traditional approach of using paper, pencil, and a calculator to develop equations for design options, Autodesk ForceEffect does all the simulation and engineering calculations for you right on your mobile device, enabling you to quickly and easily simulate design options during the concept phase to determine the viability of a design.
6. BIMx
GRAPHISOFT BIMx allows you to open and interactively explore 3D Building Information Models (BIM models) previously created with ArchiCAD, the industry-leading BIM software for architects and construction workers.
7. sightLevel
This app popular among homeowners and DIYers, but it could be used on a job site when a normal level isn’t available. It works by holding the phone in landscape view, tilting it until the bubble is centered, then using the horizontal red line to determine the slope. This could be used to determine if walls, dividers, fences, wall hangings, and picture frames are level.
8. Beam Designer
Take benefit from our engineering know how and calculate the eigenvalues, deflection and stresses for many steel beam sections. Choose different sections from our library or put in the data for your own geometry. Choose between different load cases and get all important results. Switch between sections and loads and optimize your beam design in a very simple way.
9. I.D. Wood
I.D. Wood is your Pocket Guide to Woods from around the world with full screen samples and detailed information for over 200 different woods. The standalone application will work with or without an Internet connection so that the samples and information are always at your fingertips. From the basic to the exotic, I.D. Wood turns your mobile device into a virtual guidebook for seasoned woodworkers, cabinet makers, designers, artists, architects, collectors, antique dealers, hobbyists, gunsmiths, musicians, homeowners, boat builders, carpenters and others.
10. FingerCAD
CAD application for technical drawing with fingers assisted by computer. The final design will be saved, and it can be sent via e-mail or printed.