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Small Cabin Forum / Cabin Construction / 24x20 cabin 24 being the gable end
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# Posted: 3 Jan 2022 12:31 - Edited by: ICC

Quoting: Brettny
Hurricane ties and toe nailing dont keep the walls together. Typicaly you would nail all three together, the rafter to the ceiling joist and both to the top plate. Making for a very strong triangle and the ceiling joist acting as the wall tie.


The rafter tie to rafter connection is what restrains the tension in the rafter tie that is created from the load (snow, wind,,,,) on the roof. The size and number of nails to be used for this heel joint depends on rafter span and roof load and is specified in IRC Chapter 8, Table 802.5.2. Read the footnotes too.

The hurricane ties hold the roof assembly onto the wall top plates and as a side benefit can make assembly easier. Toe nailing may not be accepted in some locations, but I see no reason to not use hurricane ties everywhere..

# Posted: 3 Jan 2022 12:47 - Edited by: ICC

Quoting: travellerw
Snow load: Ss = 1.5 kPa / Sr = 0.1 kPa. Run through a calculator that is about 18psf and I believe code says we design for 30psf
Rafter spacing 16"
Building width: 24' 12/12 pitch

24 foot bldg width, 12/12 pitch 16" O.C.
30 PSF snow load is the snow only. The general assumption is the dead load is 10 PSF, so we use 40PSF to calculate. Sometimes DL is more like 15 depending on variables.

For educational purposes only, I will run those numbers through the engineering software I have the use of for myself.

The answer it puts out is 320 lbs horizontal outwards force on each rafter tail connection.

# Posted: 3 Jan 2022 19:25 - Edited by: cvinvt

I appreciate the thoughts.

We do not have to have plans from an engineer.

The Town does not require them for a building permit.

We lean towards going with the 8 foot walls, yes.

We're not decided though.

That being said, I will investigate what it will cost to work with an Engineer for structural plans.

# Posted: 4 Jan 2022 07:13

Quoting: cvinvt
We do not have to have plans from an engineer.

That dosnt mean you should build a sub par building. That also dosnt mean you should get engineered and stamped plans either.

The connection of the wall top plate, ceiling joists/wall ties and roof rafters is one of the most important ones in a building. You could possibly use a truss style system with an "attic".

# Posted: 4 Jan 2022 10:14 - Edited by: gcrank1

Look online for 'engineer approved small cabin/cottage plans'?
Also get a book (library?) on building carpentry.
The basics of 'engineer approved involves using the proper materials and techniques. Design with those and the 'approval' part gets way easier. Even if an approved design and inspections arent required all that is sound practice.
Part of your idea for a structure should be to maximize the materials you buy (avoid wasted $), that will likely mean using the common 4x8' multiples for sheet goods as your floor and wall sizing (ie, 16x20, 20x24, etc dimensions).
The learning and planning stage can be great fun

# Posted: 4 Jan 2022 10:57 - Edited by: ICC

Quoting: gcrank1
The basics of 'engineer approved involves using the proper materials and techniques. Design with those and the 'approval' part gets way easier.

This relates directly to the IRC. The IRC is a prescriptive code. A technique that is illustrated or described in the IRC does not need any further engineering. The IRC does allow for other un-listed techniques or designs. There are many places where the catch-all phrase "accepted engineering practice" appears. When you see that phrase it is often best to backup and rethink how you want to do the task at hand. The 'accepted' part will likely involve an engineers paid for stamp of approval.

As for looking online for engineered plans, the norm is that if the plan being submitted does not meet all the criteria of the IRC, it can be rejected without having an actual stamp from an engineer licensed in whatever state the project is located.

Of course, if there is no planning or inspection department in that location you can probably do whatever you want. But that does not necessarily mean the project will be as structurally sound as it could be.

# Posted: 10 Jan 2022 22:35

I am building a 24x32 with 10 foot walls in the front half and 8 foot walls in the back with a knee wall over floor joists and 10/12 roof. Load bearing ridge with no collar ties for a true cathedral

2x6 walls, 2x10 rafters and a 3 ply 2x12 load bearing ridge beam full length with one support post at 18 feet (loft length)

This was engineered and approved by my building dept

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