Join thousands of carpenters using Loftup Spark to calculate traditional cut roofs without tables, trigonometry or guesswork. Get exact dimensions, angles and cutting lists instantly.
Download Loftup Spark
Proven tools used daily by timber framers and self-builders working on traditional roofs
Updated 09.10.2026. All features included in v3.0 download. No subscription required.
Comprehensive calculation tools built by carpenters for the carpentry community
Interactive cross-section updates in real-time as you adjust span and pitch. See your roof geometry drawn full-size before cutting a single stick.
Every timber member listed with exact lengths in millimeters. From common rafters to sprocket tails, get quantities and dimensions for the whole job.
Plumb cuts, seat cuts, and birdsmouth depths calculated instantly. Set your sliding bevel straight from the screen without consulting rafter tables.
All standard structural sizes from 47×100mm to 75×225mm. Reference tables for C16, C24, TR26, plus Douglas fir, oak, larch and glulam grades.
Point your camera at an existing roof to capture pitch and dimensions. Perfect for renovation work when you need to match or verify measurements on site.
Calculate the loft envelope showing exactly how much standing height you'll have. Essential for room-in-roof designs and planning applications.
From initial design through to final cutting list – your workflow on every traditional roof project
Loftup Spark was created after years of feedback from working carpenters and timber framers. Version 3.0 represents the culmination of that community input, delivering the most requested features in a clean, offline-first package.
No account registration. No cloud storage. No subscription fees. Just professional roof calculations that work anywhere you take your phone – from the workshop bench to the scaffolding.
The app includes illustrated guides for 10 structural members showing cut sequences, plus detailed explanations of 9 common setting-out faults with their causes, checks and fixes. It's like having an experienced carpenter looking over your shoulder.
Precision engineering for accurate calculations every time
Loftup Spark eliminates manual trigonometry by computing all rafter geometry from your span and pitch inputs. The engine calculates common rafter length using rise and run, then derives all cutting angles including plumb cuts, seat cuts and birdsmouth depths.
The app references complete British structural timber specifications covering all standard sawn sizes. Each timber grade – from C16 softwood through to oak and glulam – includes strength characteristics and recommended applications. This ensures you're specifying appropriate sections for loading conditions.
Rather than typing numbers into fields, you interact directly with a scale drawing of the roof cross-section. Drag the span line to set building width. Rotate the pitch indicator to set roof angle. Every dimension updates instantly including ridge height, rafter lengths, and all cutting angles. The visual approach reduces input errors and makes the geometry immediately clear.
iOS platform • Fully offline • No subscription • Updated October 2026
Download Loftup SparkRequires iOS device. No advertisements. Complete offline functionality. All features included in base download.