This minimum pitch is important if tiles are laid below the recommended minimum pitch there is an increased chance of water getting through which can damage the underlay and battens over a prolonged period.
Minimum roof slope for clay tile.
The international residential code irc specifies a minimum 4 12 pitch 4 inches of vertical rise for every 12 inches of horizontal run for a clay or concrete tile roof except that a pitch as low as 2 1 2 12 is allowed when two layers of underlayment are applied.
Traditionally a minimum roof pitch of 20 was recommended in bs 5534 but modern tiles and slates have now been designed for applications as low as 15.
Clay and concrete roof tiles can only be installed on roof slopes of 2 1 2 12 or greater.
Anything lower than this angle is rare and although there are specific products that can go lower 15 is the most common minimum angle for clay tiles.
For standing seam metal roof panel systems a 1 4 12 minimum roof slope is prescribed.
It is uncommon to find a roof below 15 but for those very low pitch applications there are interlocking clay pantiles available suitable for use down to 12 5.
Adapted paraphrased with permission from best practices guide to residential construction chapter on best roofing practices.
It has long been enshrined in our british standards for roofing that the minimum roof pitch for plain tiles is 35 degrees or 40 degrees for handmade clay tiles that do.
Roof slope requirements for tiled roofs.
The following table provides the minimum required allowable roof slope for each type of roofing material mentioned in the code.
Clay and concrete tile minimum roof slope roof pitch r905 3 2.
This 1 4 12 minimum roof slope requirement also applies to spray polyurethane foam spf roof systems in new construction.
For many years 20 was recommended as the minimum pitch for clay tiles but this has decreased in the modern era down to 15.
The minimum roof slope allowed by code for any type of roof is in 12 applicable only to coal tar pitch roof systems.
Concrete is long lasting with a minimum lifespan of 50 years depending on climate.
The general trend is for steeper pitch roofs which is due partly to the demand for living space in the roof.
Tile covered roof installation specifications.
The irc recommends a minimum pitch of 2 5 12 for these materials.
For metal panel roof systems with nonsoldered seams with applied lap sealant ibc 2018 prescribes a 1 2 12 minimum roof slope.
Ratios from that minimum up to 4 12 which are considered low pitch require double underlayment.
This means for every 12 horizontal units the roof must rise a minimum of two and one half vertical units.
