What do rafters sit on

Hi everyone, can someone please elaborate on the use of wooden shims between the ridge beam and the rafters? Specifically, I understand the need to make minor adjustments without having to cut some length off but I have received mixed reviews on this from a number of people. We are having new construction done and several of the rafters are not laying flush to the ridge beam.

I thank anyone in advance who can offer some commentary on my question. I subtracted for the ridge ahead of time. I believe I did everything correctly. What did I do wrong? Is this some mathematical anomaly? I have a hip roof with a pitch on the main side of the roof while the end is an pitch. How do you figure the length and angles of the cuts on an uneven roof for the hip rafter???

Enter pitch 12 inch 3. Then clear calculator 6. Enter the rise height from above 7. Then enter 8 inch pitch 8. Ben, Thanks for the response! Hello Ben, you gave a very good example here!

Why is the full 1. Robert- If you follow the procedure carefully — Notice the Ridge is deducted from the ENTIRE width of the structure first , than the result is divided in half to get the actual rafter run. I have struggled with getting rafters right forever! I have also read everything I can find and watched countless videos but never fully understood the processs untill now.

This is the best video on rafter cutting in existence. I got the calculator and followed the video instructions with perfect results!! Thank you for settting me straight. Is your shed open ceiling? What size is the shed? And what pitch is your roof? This looks like what I want to do except I want 2 ft. Tom — Thanks for your comment! I struggled for way too many years myself..

It really is pretty simple , I wish my math teacher had told me what I was going to use all that math for …… Thanks for the Photo too! Rather than outside the wall to ridge, the author made calculations from inside the wall for effective run of rafter at ridge.

This eliminates extra addition or subtraction with regard to seat cut. Height to bottom of ridge intersecting with bottom face of common rafter also easy. Bottom of ridge board for common gable roof can be set to bottom face of rafters. The method we show here is the most common in use, and it does require a little understanding of where the triangle is. I tried his method but found it to be more confusing than the traditional methods.

In addition, you become the only guy on the jobsite measuring to the inside of the plate — to me its like switching the gas and brake pedals on my car how do you hook your tape? We chose a simple Traditional approach using the modern Calculator. Better to speak the language of your trade than have to explain yourself.. So… Your triangle is fixed; your roof pitch angle is And what size width rafters are used? What adjustments in layout are made when the bearing walls are of two different widths but you want the pitch the same on both sides?

The Seat cut remains the same for both sides — The center of building is determined from outside to outside — so the ridge from the perspective of the Interior will be slightly off center. This is for a cathedral ceiling so my seat cut depth is 1. I now have approx. If the ceiling was not cathedral i. Thanks for the article. It has made my life simpler.

I especially like getting the ridge thickness issue out of the way right up front. Question: If calculating the cuts for a flat sloped roof, is the run measured then from the outside of the down slope wall to the inside of the up slope wall? James — If a roof is flat , it has no slope.

Better off drawing a Picture so we can understand what you are trying to describe. Flat as in no peak. I can easily calculate pitch and the angles for the cuts, but the formula requires span and translating the span instructions above to a non-peaked roof seems to indicate that you use the outside of the down hill wall and the inside of the up hill wall.

Extremely easy to understand. I wish I had taken the time in my youth to have learned from him. Thanks much. Well done. Disregard I just re-read above you deducted it from the width if the building not from the run of the rafter.

I know that this is an older post, but I was hoping that you could assist. I am putting together a timber frame barn and the roof trusses are half lapped at the peak. The overall width of the building in S.

Cal would be the span. Half the span is the run. Great article and videos, very informative and easy to understand. What should my cut angles be? I do not have one of those nifty stair squares. Stick built every roof. I feel any method you use is perfectly fine as long as the results are achieved. This is well detailed and extremely informative! The world needs more experts who can teach effectively! Thanks for keeping this info on the web for so long.

Why is he showing the rise as meeting in the middle of the ridge. The rise is from the TOP of the ridge to the outside of the plate. Therefore you go from outside of plate to face of Ridge beam — the rise gets calculated , Than the HAP has to be added to get Overall finish. If you layout from the Outside of the plate to the top of the ridge and calculate , your pitch will be wrong.

Your forgetting about 3 dimensions of Framing Laying out from outside of plate to a fixed ridge height is another set of calculations not discussed here. Ok first off i want to say i do not use a construction calculator at all. On a piece of paper I write 10 over 12 on one side and to the right of that i write I then cross multiply and divide to find the rise. For example The confused use of pitch and slope on the internet is really annoying.

Always have to read closely to determine which it actually intended. The Calculator uses the term Pitch because it is now the most common usage of the Term. I travel all around the country teaching carpenters and I am always amazed at the different terminology used.

Trimmer — Jack — Packer -Cripple all regional terms for the same element the stud under the header If you ask for a Cripple measurement in South Louisiana you might have to clarify what you want. How about this — Know what a Pork Chop is? One thing is certain, there is no need for the word police here, at least not yet. I think I qualify to add my 2 cents.

I cut my first roof well before there were calculators on the job. However, they are handy especially when calculating stair rise. Once you have determined the run; stepping off with a square and a sharp pencil and attention to accuracy is a no brainer. Make adjustments if necessary, cut off the allowance for the ridge and then use that one as a pattern to scribe the rest.

That was when I had a fold out road map trying to find a job site and stopping at a phone booth to call the homeowner for directions. Than I got one of those new fangled GPS thingys and a flip phone. That saved me a lot of time. Thats how I view the calculator , less effort smoother and faster. I calculate, cut and install — no need to dry fit — even set the ridge first — saves me dragging the stock up to the roof for a dry run. Gotta love technology. You subtract the total width of the ridge beam from both sides.

Mark — If you follow the Math as it was presented , deducting the entire ridge Before you divide the Span in half is the same thing as cutting the span in half than deducting half of the ridge.

Your rafter only goes to the face of the ridge —. I enjoyed scanning through your article. If it is there I missed it, but how do you use this information to determine the cuts for a gambrel roof?

I am trying to find the correct formula or method to place a gambrel roof on a shed I am building this coming year. To not make a pun, you totally nailed it! I was so confused looking at different Youtube videos where details and the pictures were lacking. I find when trying to learned from these open information sources that I have to incorporate multiple explanations from different sources.

I believe some videos I watched left out the outside thickness when figuring span. Your explanation has been best so far from what I can see. Always expressed as a fraction. I taught for 20 years in a state prison. I had to use the KISS method. With a house-attached overhead, rafters are fastened to the house at one end. Metal framing connectors make the best connections. Joist hangers can hang rafters from a ledger, but, for sloping rafters, notch them or use special rafter hangers.

If rafters will sit on top of a ledger, attach them with seismic anchors as you would attach rafters to a beam. To do this, butt the ends of the rafters together over a supporting beam. Then nail two pieces of 1-by or 2-by lumber of the same width as the rafters as show at left and about 18 inches long centered over both sides of the splice. Or, join the members using manufactured metal splice plates. Be sure each rafter end sits a full inch on the supporting beam. If you must splice several rafters, stagger the splices over different beams to prevent a weak substructure.

Another splicing method—though it does not utilize uniform spacing—is to overlap the rafter ends that are supported by beams. If more than one splice is needed on a full rafter length, alternate overlapped sides.

For standard 2-inch lumber, nail both faces of each splice with six 8d or 10d common galvanized nails. This type of splicing, as shown above right, adds lateral stability to the rafters and may eliminate the need for bracing.

Fitting sloped rafters in place can be tricky for a novice. To cut sloping rafters for a house-attached patio roof, lay a rafter board so it rests on its edge on both the ledger and the beam parallel to the ledger. Below is an image of the common rafter as it is used in roof framing. If you familiarize yourself with the components that make up the rafter it should assist you in this roof framing task. In this rafter tutorial we will be using a hypothetical roof framing situation. We will be figuring the pitch, rafter length, lumber size, and on center spacing for the rafters.

Determine Span : This is accomplished by measuring the overall width of the building where rafters are to sit. In our case this is 24 feet. This is the horizontal distance the rafter travels to meet the one from the other side. Determine Lumber Size and O. Spacing : When determining lumber size to be used in roof framing keep in mind to use the horizontal run of the rafter not the length or span.

I use the American Wood Council rafter span calculator. In our case the lumber will be 2 x 6 S-P-F 2 on 16" centers. I have discussed alternative methods.

There is also an online rafter calculator. I always take the width of the ridge board out when figuring out my rafter length. In this case we will be using a 2x8 ridge board. When roof framing always use the next larger size lumber than rafters for the ridge board to achieve full bearing. Here are the sequence of key strokes for the Construction Master Calculator. The diagonal number is the measurement from the ridge board to the outside edge of the wall it will sit on.

After adding the length of the tail we will need 16 foot lumber for this job. When ordering lumber do not forget the length of the eave.

Select Rafter Stock : From the lumber pile find a straight and light 16 foot 2x6.