What is roof pitch and how is it expressed?

Roof pitch describes the angle of the roof surface relative to the horizontal. It is expressed in degrees, percent or as a ratio. 45 degrees equals 100% slope (ratio 1:1). In Germany, pitches between 20 and 45 degrees are common.

How do you calculate rafter length?

Rafter length is calculated from half the building width (for gable roofs) and the pitch angle: rafter length = half width / cos(angle). With overhang: rafter length = (half width + overhang) / cos(angle). For a 10 m wide building at 35 degrees with 50 cm overhang: (5 + 0.5) / cos(35) = 6.71 m.

What formula is used for roof area?

For a gable roof: roof area = 2 x rafter length x (building length + 2 x overhang). The rafter length includes the eave overhang. Roof area is always larger than floor area since the sloped surface is longer than the horizontal projection.

Which snow load zone is my location in?

Germany is divided into 5 snow load zones (Zone 1 to 3). Northern German lowlands are typically in Zone 1, central mountain ranges in Zone 2, Alpine foothills in Zone 2a or 3. The exact assignment follows DIN EN 1991-1-3 Annex NA. Your local building authority can provide guidance.

What minimum pitch do roof tiles need?

Clay and concrete roof tiles require a minimum pitch of 22 degrees. Slate needs 25 degrees, asphalt shingles 15 degrees, standing seam metal just 7 degrees and trapezoidal metal 5 degrees. EPDM membranes can be used from 2 degrees. Below the prescribed minimum, leaks may occur.

What is the difference between a gable and hip roof?

In a gable roof, the roof surfaces end vertically at the gable sides, creating triangular gable walls. In a hip roof, the gable sides are also sloped (hipped), so no vertical gable walls exist. A hip roof therefore has more roof area but less wall area and is more wind-resistant.

What purpose does a roof overhang serve?

Roof overhang protects the facade and base area from driving rain and direct sunlight. Typical overhangs are 30 to 80 cm. A larger overhang provides more protection but requires longer rafters. On the gable side, the overhang is called the rake.

At what pitch is a roof considered flat?

A roof is considered flat at a pitch below 5 degrees (approx. 8.7%). Most flat roofs have a pitch of 2 to 3 degrees for drainage. Between 5 and 20 degrees, it is called a low-slope roof.

How do I measure the pitch of an existing roof?

Easiest with a digital spirit level on a rafter or roof tile. Alternatively, measure the horizontal run and the rise in the attic and calculate the angle: arctan(rise / run). Smartphone apps with inclinometers also work.

How much does a new roof covering cost per m2?

Costs vary greatly by material: concrete tiles 20-35 EUR/sqm, clay tiles 25-50 EUR/sqm, asphalt shingles 15-30 EUR/sqm, standing seam metal 50-90 EUR/sqm, slate 80-140 EUR/sqm. These prices include material and installation but not battens and underlay.

Roof Tiles or Metal? Costs & Minimum Pitch | Roof Calculator

Comparing the Main Roofing Materials

When choosing a roofing material, three factors play the primary role: cost, minimum pitch and lifespan. We compare the five most common materials in Germany: clay tiles, concrete tiles, slate, standing seam metal and asphalt shingles.

Clay Tiles: The Classic Choice

Clay tiles are made from natural clay fired at high temperatures and have been the standard roofing material in Germany for centuries. They are available in numerous profiles: plain tiles (Biberschwanz), interlocking tiles (Frankfurter Pfanne), and many more.

Cost: 25 to 50 EUR/sqm (material + installation). Premium brands like Erlus or Creaton sit at the upper end. Minimum pitch: 22 degrees. Lifespan: 50 to 80 years.

Advantages: Natural building material, excellent durability, wide variety of shapes and colors, good moisture management (breathes), individual tiles easily replaceable when damaged.

Disadvantages: Relatively heavy (approx. 40-50 kg/sqm), high minimum pitch, prone to moss growth in shaded locations, inferior tiles may crack in frost.

Concrete Tiles: The Affordable Alternative

Concrete tiles (market leader: Braas) consist of cement, sand and water. They are significantly cheaper than clay tiles and offer similar performance.

Cost: 20 to 35 EUR/sqm. Minimum pitch: 22 degrees. Lifespan: 30 to 50 years (shorter than clay). They are heavier than clay tiles (approx. 45-55 kg/sqm) and can fade over time.

Slate: The Premium Material

Slate is a natural stone split into thin sheets. In Germany, Moselle slate is the best known. Slate roofs are commonly found on historic buildings in the Rhineland, Eifel and Bergisch Land regions.

Cost: 80 to 140 EUR/sqm. Minimum pitch: 25 degrees. Lifespan: 80 to 150 years (the most durable material). The material is expensive, installation requires specialist skills, and not every roofer can work with slate.

Standing Seam Metal: Light and Flexible

Standing seam metal consists of zinc-coated steel, aluminum or copper. The sheets are joined with standing seams, creating a rainproof connection. The system works for pitches from 7 degrees.

Cost: 50 to 90 EUR/sqm (steel). Copper and zinc are significantly more expensive (100-200 EUR/sqm). Lifespan: 40 to 70 years. Advantages: Low weight (approx. 5-10 kg/sqm), low minimum pitch, fast installation, low maintenance.

Disadvantages: Higher initial investment than tiles, condensation issues (ventilation required), not aesthetically suited to every building, louder than tiles in rain.

Asphalt Shingles: The Budget Solution

Asphalt shingles consist of fiberglass mat saturated with bitumen and coated with mineral granules. They are lightweight, inexpensive and easy to install.

Cost: 15 to 30 EUR/sqm. Minimum pitch: 15 degrees. Lifespan: 20 to 35 years (the shortest of all options). They are suitable for garden sheds, carports and simple roofs, but not for quality residential buildings.

Cost Comparison for a Typical Roof

For a 170 sqm gable roof (10 x 12 m, 35 degrees), approximate material costs (excluding battens and underlay): Concrete tiles: 3,400-5,950 EUR. Clay tiles: 4,250-8,500 EUR. Asphalt shingles: 2,550-5,100 EUR. Standing seam metal: 8,500-15,300 EUR. Slate: 13,600-23,800 EUR.

In addition, every roof requires battens (approx. 8-12 EUR/sqm), underlay membrane (approx. 3-5 EUR/sqm), insulation (15-40 EUR/sqm), gutters, snow guards and accessories.