Rafter Skills Tech

Welcome to Rafter Skills

Rafter Skills is an online platform for anyone who is interested in advancing their skill sets in cut roofing by gaining further knowledge and a deeper understanding of this very interesting subject. My aim is to guide others through this and assist you in advance and exceeding in your expectations. Allow me to walk you through this procedure step-by-step during online sessions that are geared towards assisting others to master various types of roofs, from simple to advanced including Irregular Hip & Valley Roofs.

This is a flexible way to learn, some people don't feel comfortable with doing the calculations in this case they can take part by learning from the drawings and geometry then by building the model without going into all the calculations. Sometimes this can be the best option and its how I started off when taking part in other advanced carpentry courses.

Then there's the option for others who prefer to do a mix of learning from the drawings, geometry and also by applying calculations to find all the lengths and angles. Then its a mater of moving on to test it all out by building the model. It’s just like everything else there are methods of good practice in bringing this all together without a lot of guessing and trial and error! Different parts of this can be really interesting and sometimes addictive in the hunger for knowledge, it can be a learning curve to grasp and to cherish in this very special area of carpentry and roof framing.

Meet the Coach

Hi, I'm Tommy. With 45 years of experience in carpentry and joinery, my absolute passion has always been the art and precision that’s involved with roof cutting. This lifelong obsession was fueled by learning from master tradesmen at home and abroad, pursuing advanced studies, and delving into every book and video available.

After decades of refining my skills on site, l've shifted my focus to what I love most: coaching and mentoring the next generation. I've made the mistakes, mastered the shortcuts, figured out the geometry and the calculations so you don't have to.

Let me take you on a journey into the precision and mastery of this incredible craft and help you build these roofs with confidence.

Shoot for the stars! Don't let anything or anyone put you off!

This is all transferable information and when you know how to find the different angles and lengths by using basic trig calculations it can also lead you on to calculating for full scale roofing projects. There really isn’t much indepth information out there and knowing how to calculate in relation to what’s going on with the geometry is key to figuring out other more challenging roofs like irregular pitch roofs, also known as roofs that have bastard hips or valley rafters.

When it comes to irregular pitched roofs again we will be using metric and degrees. We will cover the important points that need to be taken into consideration to bring it all together in practice. In my view as a carpenter with over 40 years of experience these types of roofs are some of the most interesting that I've came across and a challange for carpenters to really conquer.

Just let me reassure you, don't let any part of this put you off because I've met a lot of guys over the years who said they would never be able to grasp the math's or maybe the geometry or the more technical side of roof cutting but it's all about having the right mindset. This was the case in my own experience, math's at school wasn't interesting for me but when I started working as a carpenter doing roofs and wanting to solve the angles and lengths of the different rafters I started to really focus on learning how to do this. It wasn't long before it began to pay off and became a real game changer. The secret is to actually believe that you can learn how to do this and this is where I come in to coach and guide you through the parts that are holding you back.

During my carpentry career, I discovered other historic, traditional geometric methods like stereotomy and Schiftung. These methods mainly relied on the geometry being drawn out in full scale with the need for math calculations kept to a minimum. These drawing methods are the backbone of modern roof framing and carpenters all around the world use drawing principles like this daily without realising it, whether folding out and developing surfaces from the plan drawings to determine rafter lengths and angles. Then there's an old school direct method: mainly used when cutting the rafters with a hand saw, the plumb line on the end of the rafter is first marked on one side and shifted on the other side of hip and jack rafters to obtain their side cuts. Then in another case when cutting with a portable power saw the saw blade is tilted to the plan angle to cut these side cut angles.

Rafterskills offers a step-by-step coaching that's designed to simplify and link the geometry, the rafter calculations and the practical methods together for a deeper understanding of cut roof framing. Some of the drawings and basic trig calculations at first glance can feel intimidating, but they are highly learnable with the right guidance. Understanding these methods and practicing them is what separates an average roof framer, carpenter from someone who has limited knowledge and skills to someone who has advanced knowledge and skills.

Do you know of any Technical college teaching this level of advanced roof framing ?
Do you know of any online courses that use metric measurement and degrees ?
Do you know other carpenters who know cut roof framing at this level ?
Do you want to have this knowledge and apply it to your own personal skill set within this craft ?

Here at Rafterskills you can build your knowledge, your skills and expertise!

If you want to master these tried and tested methods to elevate your knowledge and advance your roof cutting skills, you can reach us by dropping an email to rafterskills@gmail.com

Don’t miss out! This coaching is a limited offer and won’t always be available!

How will this work?

Why learn the technical side of roof framing and the mathematics behind its geometry?

Because knowing methods like this unlocks a deeper understanding of how more advanced roofs are marked out cut and built. The lines on a drawing provide the visual framework, while geometry reveals how angles, shapes, and lengths interact in both 2D and 3D space.

Geometry is the foundation-it develops the ability to think visually, interpret complex forms, and solve problems. Mathematics then complements this understanding by linking the two with speed, precision and accuracy.

Then there's another plus, the practical, hands-on methods. Merging practical experience and skills with sound technical knowledge gives the carpenter a powerful edge. It sharpens craftsmanship, builds confidence, and enhances problem-solving abilities.

Understanding these methods and practicing them is what separates an average roof framer, carpenter from someone who has limited knowledge and skills to someone who would have advanced knowledge and skills and is a personal statement of passion and dedication within the craft.

During online lessons the information will be transferred in step by step instructions that will cover the in-depth details that form the roof framework. First of all you gain the knowledge from proven methods along with many other practical tips for bringing it all together in practice by using your skills to build each model.

These course models range from basic to advanced and cover an introduction in how to read the working drawings and the geometry involved for building these models. This can include the mathematical calculations for the lengths and angles that are used to build these Roof structures in their scaled down form, and when it’s full scale on site its much of the same process.

Just to give you an idea of how this can work, the online sessions will mainly be focused on how to go about doing this and to give you the best chance of grasping the lesson with minimal time spent online, most of the time the camera would be in the downward position for you to observe what's going on and in helping you to follow the lesson with the least amount of distraction. During each lesson any questions that you have will also be addressed and I will do my best to answer them as we proceed. I can only recommend that you build the roof model when you are ready, as this is one of the best ways to test your learning by bringing it all together in practice.

This is all geared towards practicing knowledge and improving skills, don't be put off by the fact that these are scaled models, these models can be key learning! Its the old proven recipe in this case, of learning the theory behind the drawings and geometry, before moving on to apply math calculations by using some basic trigonometry to find the lengths and angles of the different rafters within roof framework, before bringing it all together in practice.

Just a few more points

In my experience I've found that some people tend to shy away from geometry and trigonometry but other people can be surprised at how quickly they begin to adapt and relate to using methods like this. Just to let me remind you, I'm going to pass this on to you as a carpenter by looking at the drawings, and in using some basic trig calculations to find the rafter lengths and angles.

Why use trigonometry to calculate rafter lengths and angles as opposed to apps and tables etc! First of using apps and tables will only take you so far and using tables for ready reckoner books will only work for Regular pitched roofs. Trigonometry is also a universal method for calculating angles and lengths, it is used in building and construction by engineers, surveyors and architects etc and becoming more familiar with using it can lead to career extension and job promotion. If you haven’t used trigonometry before, it’s just a matter of becoming familiar with using one or 2 formulas, in this case to calculate rafters before moving on to the next step in calculating other dimensions and angles that can lead on to further understanding and calculating of other more challenging roofs.

The drawing out the details may not be for everyone but understanding them can play an important part in helping us to visualise or in building a kind of map in our minds as to what these lines represent. When we look at the drawing for these models and can also check the lengths and angles with some calculations it plays another important part in building our trust and confidence in the process and in reassuring ourselves that things are working out well. Then when we become more familiar with doing calculations for some of these steps we can get by with the minimum of drawings.

Starting off at Roof Cutting

1: More about Starting off at Roof Cutting

This part can build a solid foundation for future learning and development and is best suited for people who are just starting off or returning to cut roofing. We can go through this by bridging the gap between what's written and drawn on paper to transfering the information onto the wood at hand to obtain each member of the roof structure.

Basically we would go through this step by step and any of the parts that you are already familiar with we would simply move on and a lot more of the interesting stuff will be explained to you as we go along.

One of the first things is to become familiar with some of the key terms used, Span, Run, Rise, Pitch etc, and the components that make up the roof framework, Wallplates, Common rafters, Jack rafters etc. Then we move on to reading the basic drawings a drawing of a scaled version of a roof plan and elevation view. Learn about the different tools that are used for marking the angles, speed square and steel square.

Calculating the lengths and angles using some basic trigonometry then measuring and marking out the first pair of rafters, cutting the plumb cut and the birdsmouth that allows the rafters to sit securely on the wall plate. All of this will be explained and how to get accurate results to milimeter perfection! Testing and trying the first pair of rafters right is one the most satisfying "aha!" moments when starting to learn this stuff. Then it's building a model of a gable roof frame, this brings the learning from the details on the paper and the practice of transferring this information of the lengths and angles of the different members, cutting and erecting the roof framework and bringing it all together in practice.

Starting off on a good solid foundation can play a big part in grasping the methods and the process used Why use trigonometry to calculate rafter lengths and angles as opposed to apps and tables etc! First of using apps and tables will only take you so far and using tables for ready reckoner books will only work for Regular pitched roofs. Trigonometry is also a universal method used to calculate angles and lengths, it's used in building and construction by engineers, surveyors and architects etc and becoming more familiar with using it can lead to career extension and job promotion. If you haven’t used trigonometry before, it’s just a matter of becoming familiar with using one or 2 formulas, in this case to calculate rafters before moving on to the next step in calculating other dimensions and angles that can lead on to further understanding and calculating of other more challenging roofs.

If you haven’t used trigonometry before, the first time you calculate a pair of rafters using this simple formula using (half the span) ÷ (pitch of roof) = the length of the rafter, for example lets say the half span distance is 1250 ÷ cos (35) =-1,383mm. Try it out, even cut a pair of rafters. From here it’s just a matter of moving on to the next step in calculating other dimensions and angles and it all leads on to further understanding and calculating for other more complex roofs.

Experience a learning adventure unlike any other!

Regular Hip Roofs

2: More about Regular Hip & Valley Roofs

Regular Hip & Valley Roofs are roofs that have an equal angle of pitch on all sides. During these online lessons with the aid of drawings, calculations and a model I can take you through the step by step process of how Regular pitched Hip & Valley Roofs can be worked out. This will be explained by first of all looking at the drawings and the geometry to become more familiar with them before moving on to calculating the rafter lengths and angles using some basic trigonometry. This includes all the important points that are necessary to bring it all together in practice.

Here you can learn how to draw out and also calculate all the lengths and angles for the 10 different Rafters that are listed below. This will cover information about the HAP "height above plate" settings, cases when the Hip or Valley rafters have a square top edge and when they have backing bevels applied.

1. Rafter plum bevel

2. Common Rafter level cut

3. Hip Rafter plumb cut

4. Hip Rafter level or seat cut

5. Hip Rafter side cut

6. Hip Backing angle

7. Jack Rafter side cut

8. Purlin face bevel

9. Purlin edge bevel

10. Purlin lip bevel

This can include looking at the geometry and steel square settings for all of these angles even though you may not use them all, it's good practice within the craft and as a tradesperson to have the know-how! and this applies to other aspects of this learning that lead to a more comprehensive understanding of the subject.

This can also include making adjustments for different types of ridge, ridge board and ridge beams, purlins, vertical and tilted, along with the different methods and tools used for marking out.

Experience a learning adventure unlike any other!

Ridge, Hip & Valley Intersections

The 1st picture below shows an example of a roof plan with different intersecting rafters. The pictures below show how to find the connecting angles of the Ridge, Hip and Valley Rafters. In the 2nd picture a section of the ridge, hip & valley rafters have been drawn out to the plan angles, in the true thickness of materials. The 3rd picture shows these connecting parts cut and assembled with backing bevels applied to the ridge, hip & valley rafters showing all the center lines meeting at the intersection points in elevation. The 4th picture shows the connecting parts cut and assembled when the ridge and rafters have square edges. Much more can be seen from different side view angles but this is just to give a general understanding of the 2 different methods and how the rafters with square edges are cut and set in the correct position for the roof surfaces to smoothly plane in with each other.

Irregular Hip & Valley Roofs

This is all about Irregular Pitch Hip & Valley Roofs. These types of roofs have different roof pitches on either side of the Hip or Valley intersection.

3: More about Irregular Hip & Valley Roofs

When we challenge ourselves with the task of conquering Irregular Hip & Valley Roofs it starts to give us a new insight into roof framing at a whole new level. These types of roofs are often referred to as roofs that have bastard Hip or Valley Rafters. Irregular Hip and Valley roofs have 2 different roof pitches that plain in to meet at an intersecting Hip or Valley rafter, this affects a number of things including the Hip and Valley plan angles and the Hip, Valley and Jack Rafter side cuts.

The Irregular Hip & Valley roofs are really interesting roofs to get a grasp of, they can put some of the best to the test. In cases where the 2 different roof pitches have an equal soffit overhang distance the Hip and Valley rafters do not sit on the corner of the wallplate and this normally requires the steeper pitched rafters to have a raised or higher wallplate. Then there are other important points to consider and how they affect the roof geometry and the calculations. Here you can learn how to take these factors into consideration and how to bring them all together in practice.

These types of Roofs can be a learning curve that opens our minds to a whole new way of thinking and understanding of calculating, cutting and pitching roofs. During these online sessions let me guide you through this using a step by step approach in assisting you to conquer these types of roofs. This will be explained by first of all looking at the drawings and the geometry before calculating the rafter lengths and angles.

During each step I'm also going to explain and show how to calculate the lengths and angles by using some basic trigonometry. If you’re not familiar with using trigonometry, don’t let it put you off. I'm going to explain this as a carpenter and in relation to solving Rafter lengths and angles, it’s just a matter of getting familiar with using one formula before moving onto the next one.

In the first part I'm going to show you how to draw this out and explain what the different lines represent and how it all relates in practice by using a model of the roof. Some people have asked me, "how is all of this going to benefit me when it involves doing a full scale roof ?" and the answer is that it’s much of the same process used for example it could also be calculating for a materials list.

The drawing out the details may not be for everyone but understanding them can play an important part in helping us to visualise or in building a kind of map in the mind as to what these lines represent. When we look at the drawing and can also check the lengths and angles with some calculations it plays another important part in building our trust and confidence in the process and in reassuring ourselves that things are working out well. Then when we become more familiar with the calculations for some of these steps we can get by with the minimum of drawings.

The photo above showing the plan layout for this irregular Hip intersection and 2 different methods of jointing the Hip Rafter to the Ridge Board. The photo below shows an example of the 2 different roof pitches and the angle of the Hip in elevation. This can all be explained in detail and how to bring it all together in practice.

The model above is an Irregular Hip Rafter with intersecting pitches of 30 and 40 degrees.

The model below is an Irregular Valley Rafter with intersecting pitches of 30 and 40 degrees.

In this case the model below shows a Lay-board that has square edges .

In this case the model below shows a Roof that has an Irregular Valley intersection, in this model the Valley lay-board has a bevel applied to the edge of the board.

The first model below shows a downward view of the plan angles for the Valley lay-boards connecting from a 40° pitch roof and intersecting onto a 30° pitch roof.

This model below shows a downward view of the plan angles for the Valley lay-boards connecting from a 30° pitch roof and intersecting onto a 40° pitch roof.

These examples show some of the differences when the Roof pitches are reversed. During these lessons we can go into calculating the Rafter lengths, Backing angles, Valley layboard lengths and angles by using the measurements from the drawings and by using some other short cut trig formulas. This is all part of further understanding becoming more familiar and in building confidence in conquering some of the challenges that these Roofs can throw at us.

Experience a learning adventure unlike any other!

Contact & Booking

These courses are available online, in English language and accessible to you wherever you are based around the globe. This is a flexible form of booking, it's up to you to decide, we only need to agree on a date and time slot for the booking and we can take it from there. The video link-up can be done using WhatsApp or FaceTime on your smartphone or tablet.

If you are interested in any part of this please send a message by email to rafterskills@gmail.com

Irregular Hip with Witches cut "Hexenschnitt" and Splayed Fascia

This model was first of all completed with the rafters cut plumb and then as a futher study the rafters were cut square and this completly changes the geometry and the angles for the over cuts on the hip rafter and the angles for the splayed cut fascia. The Hexenschnitt is a historic part of traditional European carpentry and has been used in roof design in various parts of America. These hip rafter cuts are also known as the witches cut, because legend has it a witches spell was cast on it and the carpenter was tasked with solving the angles.

The drawing above shows the plan drawing for an irregular hip roof model, these setting out points and the positioning of the rafters are key for starting off the model and when building in full scale.

The steeper 40 degree requires the wallplate to be raised and set at a higher level, all of these different points will be expained from the drawings and how to bring it all together in practice.

The first photo below shows and irregular hip rafter that has square edges and is shifted from its center line to obtain equal shoulder heights. The second photo shows the hip when centered and in this case 2 different backing bevels are applied, they form unequal shoulder heights and this allows the hip to plain in with the different pitched rafters on each side.

4: Roof with Curved Rafters

Roof with Curved and Backed Hip, First of all we need to know some information, in this case it’s the run of the common Rafters, the pitch of the roof and the chord distance from its springing line. From here we can calculate the curve for the common Rafters, Hip Rafter and the curved Backing angle.

Jack Rafter Claw Angles

This was a study of the Jack rafter claw angles in a case where it meets the underside of the Hip rafter. his For most of us in construction this is something we are not going to use very often, but its an exercise in angle study and improving visual thinking and skills in practice. The drawing below was the 1st stage and it was drawn out on a piece of white melamine faced hardboard. The 2nd stage involved figuring out the math calculations and the results for these claw angles were compaired as a check. Then the 3rd stage was to build a simple model to bring it all together in practice and as a confidence building excercise for me and in assuring me that i'm getting the correct results.

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