The Forestry Forum is sponsored in part by:


Forestry Forum
Sponsored by:


TimberKing Sawmills



Toll Free 1-800-582-0470

LogRite Tools



Norwood Industries Inc.


Sawmill & Woodlot Magazine



Your source for Portable Sawmills, Edgers, Resaws, Sharpeners, Setters, Bandsaw Blades and Sawmill Parts

EZ Boardwalk Sawmills. More Saw For Less Money!

STIHLDealers.com sponsored by Northeast STIHL


Woodland Sawmills

Peterson Swingmills

 KASCO SharpTech WoodMaxx Blades

Turbosawmill

Sawmill Exchange

BRUTE FORCE Authorized Dealer

Woodshax Outdoor Vending Solutions

FARMA


Council Tool

Baker Products

ECHO-Bearcat

Arborwear



Author Topic: half lap rafter peak  (Read 526 times)

0 Members and 1 Guest are viewing this topic.

Offline Christopher J

  • member
  • *
  • Posts: 2
  • I'm new!
    • Share Post
half lap rafter peak
« on: December 28, 2017, 09:10:07 PM »
I'm wanting to use half laps for my garden building's roof rafters at the peak. I am doing a 4 in 12 pitched roof. The building is 8' x 12' with the gable ends over the 8-foot sides. I cannot seem to cut the half laps correctly.. so that they mate properly.  I routinely use half laps but never on an angle cut.  If anyone can offer insights I'd very much appreciate it. Thank you.

Online Don P

  • Senior Member x2
  • *****
  • Posts: 4574
  • Location: Southwestern VA
  • Gender: Male
    • Share Post
    • Calculator Index
Re: half lap rafter peak
« Reply #1 on: December 28, 2017, 10:36:06 PM »
Sketchup is an easy way to find angles if that is where the problem is, 36.9.

Offline Roger Nair

  • Full Member x2
  • ***
  • Posts: 210
  • Age: 68
  • Location: Bakerton WVa
  • Gender: Male
  • I'm new!
    • Share Post
Re: half lap rafter peak
« Reply #2 on: December 28, 2017, 10:44:14 PM »
I am guessing you have tried using slope ratios to solve the layout and it was a no go.  To use slopes you will have to draw a level line and then project 4/12 from the level line.  Work at it, you'll get it'

Easier is to convert 4/12 slope into degrees of arc, sketch it out and use geometric reasoning to get the angle.

Easiest is to snap intersecting lines on the deck that correspond to the two roof surfaces, lay down rafters to the lines and transfer marks.

One method is valid as any of the others, be a good student and work through each method, you will profit with understanding.  I know this is vague but struggle will pay off.
An optimist believes this is the best of all possible worlds, the pessimist fears that the optimist is correct.--James Branch Cabell

Offline Christopher J

  • member
  • *
  • Posts: 2
  • I'm new!
    • Share Post
Re: half lap rafter peak
« Reply #3 on: December 29, 2017, 03:29:44 PM »
Thank you. Pushing ahead. Will let you know!

Offline Roger Nair

  • Full Member x2
  • ***
  • Posts: 210
  • Age: 68
  • Location: Bakerton WVa
  • Gender: Male
  • I'm new!
    • Share Post
Re: half lap rafter peak
« Reply #4 on: December 29, 2017, 08:08:50 PM »
Since it's still early, I'd like to expand one the method of using slope ratios to develop the angles needed for half-lap rafter peaks.  Using Don P's drawing as the visual reference, let's describe the situation from the point of reference of the peak intersection, the rafters descend from the peak by opposite but equal slopes, 4/12.  So when we use slope in layout we are referencing from vertical and horizontal lines or planes.  Keeping the drawing in mind and extending the lines of the rafters in their uncut state, draw a horizontal line through the peak and you will visually see the equal and opposite slope of the two rafters.  Onto the rafter stock, let's assume the rafter seat cuts and rafter length to the peak is known and marked on the rafter stock.  Go to the peak and place the framing square on the rafter with the 12 at the peak and the 4 on the down slope, mark the line from the peak across the stock.  That is the level line reference for the next step.  At this point you might encounter a level line is to short for using 4/12 slope, so you can use any multiple of 1/3, which is the simple root ratio, let's say 2/6 works.  Hold 6 at the peak and 2 from the level line with the slope in a descending direction, mark peak to 2 inch mark.  That should get you everything you need to establish the basic angles.

I hope this can be worked out from my explanation.  Once you see the reasoning, one can handle the problem with carpentry layout tools without need for calculators, trig or computer design tools.

I have edited out a mistake, I am doing this without the aid of a square and a test board. 
An optimist believes this is the best of all possible worlds, the pessimist fears that the optimist is correct.--James Branch Cabell

Online Don P

  • Senior Member x2
  • *****
  • Posts: 4574
  • Location: Southwestern VA
  • Gender: Male
    • Share Post
    • Calculator Index
Re: half lap rafter peak
« Reply #5 on: December 29, 2017, 08:20:01 PM »
I proudly showed Dad some computer calculators I made to give a bunch of roof angle cuts. His response, "It's all on your framing square". But, the first way he showed me to layout a roof was to loft it on the floor full size with chalklines, basically that is what I did with sketchup.


Share via delicious Share via digg Share via facebook Share via linkedin Share via pinterest Share via reddit Share via stumble Share via tumblr Share via twitter

xx
Rafter Peak Joinery

Started by ChiselHead on Timber Framing/Log construction

6 Replies
3923 Views
Last post November 25, 2011, 04:42:38 PM
by ChiselHead
xx
Length of rafter using stepped-lapped rafter seat.

Started by Preserved on Timber Framing/Log construction

15 Replies
6088 Views
Last post June 25, 2011, 06:25:24 PM
by piller
xx
Peak Chilli

Started by Ianab on FOOD! FOOD! FOOD!

8 Replies
849 Views
Last post May 02, 2018, 08:28:33 PM
by POSTON WIDEHEAD
xx
Peak Oil and Forestry

Started by Tarm on General Board

3 Replies
904 Views
Last post May 30, 2004, 01:05:24 PM
by SwampDonkey
 


Powered by EzPortal