Bracing for small house without OSB

[blackarrow]

Hello
We plan to build a small house on foundations. The house is about 3.5 x 8 m big with a gable roof (45 degrees) and a loft. The height of the walls is 2.5 m.
Basically, it will be a stick frame construction with 6x10 cm studs. The two big 8 m long beams (10x20 cm) will support 14 smaller beams 3.2 long (8x14 cm) and will form the bottom of the house. The two big beams will be put onto 8 reinforced concrete pier foundations.
Now, I think about bracing the walls and roof properly. There are some bigger windows on the shorter walls (3.5 m). We do not want to use OSB for bracing, but rather additional diagonal timber or metal strips (except for the bottom).
The frame will be insulated with 10 cm of non-combustible insulation. After putting the vapor barrier the interior will be covered with tongue and groove stock (14 cm wide).
Is this possible and are there some rules on how the bracing should be done? There is a sketch of how I imagined it. The four walls would be braced with additional diagonal timber. The rafters have a ridge that supports them as well as joists. I did not sketch header/trimmer, these will be of course constructed.



 

Could this work?

[scsmith42]

In older houses (pre OSB sheathing) in the US it was common to inlay a 1x4 into the 2x4 wall studs at angles similar to what you depict in your drawing.  A circular saw would be used to make several cuts 1" deep into the 2x4 and then the kerf cuts chiseled out for the 1x4 to sit flush with the outside of the studs.

It was also common to nail 2x4's at angles across the top side of the bottom chord of the trusses to provide additional torsional stability to the structure.  Basically spanning from wall to wall in the corners.

[Don P]

The building code calls that Let In Bracing (LIB). It develops a fraction of the strength of plywood sheathing (WSP) or diagonal wood board sheathing (DWB). You'll find those abbreviations in the bracing tables here around section 602.10;
CHAPTER 6 WALL CONSTRUCTION, 2018 Virginia Residential Code | ICC Digital Codes (iccsafe.org)

There is no need to brace a structure that is on a set of unbraced toothpicks. Braced walls are installed in line, over a full perimeter bracing foundation. The lateral bracing is most obvious but notice the bracing and vertical loads from above have no relationship with the supporting piers below. People also neglect to think about the load from porches, stoops and decks on the sill beam that is spanning between toothpicks. The design is for a modern fully supported floor system and a house on top. Someone stole that foundation and stuck those piers there. Go find that hoodlum and get your foundation back.

[Ljohnsaw]

You stuck a nerve in Don with your pier 'foundations'. You need a perimeter (block) foundation to support your structure correctly.

Then, the let in braces would span from the top plate to the sole plate.

[Ianab]

I guess  different building styles in different places. Here in NZ "pier" foundations and let in braces the SC describer were the common method. Done right it can be plenty strong enough. Old houses built like that get picked up and moved around all the time. It's not uncommon to see a full size 3 bedroom house heading down the road on the back of truck, doing 60 mph.  Reach it's new location and they jack it off the trailer and set it down on new piles. No perimeter foundation at all, and the space underneath has to be ventilated to reduce moisture. 

Like I said different climate and building styles. It wouldn't be suitable for a colder climate where you have to worry about the ground freezing. Also as Don points out, you want the bracing to link to the support points, and there would be more of those, maybe 50 or so for a regular house. 

Modern houses now use structural ply as bracing, it's both stronger and quicker to assemble, but an older place like mine (60s) is old school bracing and sitting on piles. 

[Ljohnsaw]

Not meaning to be argumentative. By 'correctly', I mean to current code. 

I built my little 6'x8' bathhouse on 9 piers. They were made up of 2'+ deep columns down to rock where the code called for only 2' for frost.

[Don P]

Yup, I have definite opinions and my piers have feet  :D, but I can provide the rules for here  . What I'm busting the design for is lack of a continuous load path. I also believe there is a max angle of 45 degrees on that LIB and it has a capacity. 
[color=rgba(0, 0, 0, 0.87)]R404.1.9.3 Masonry piers supporting braced wall panels.[/color]

[color=rgba(0, 0, 0, 0.87)]Masonry piers supporting braced wall panels shall be designed in accordance with accepted engineering practice.[/color]

Ian, citation please, give us a link to how that is properly done to some standard. 

[Ianab]

Ian, citation please, give us a link to how that is properly done to some standard. 

The current building regulations are here, but that's ~450 page pdf. 
https://www.building.govt.nz/building-code-compliance/how-the-building-code-works/using-nzs-3604-timber-framed-buildings/#jumpto-nzs-3604__003a2011-is-free-to-download

But it goes into how the piles need to be installed, the sub-floor attached etc. Other sections go into the specifics for different earthquake / winds / snow risks and how the wall bracing needs to be laid out. Obviously that's more about ply bracing in the modern standards, but the idea is the same. When a house gets designed now it's all done in software that designs the bracing / trusses etc based on the draughtsman inputting the floor plan. That provides the cutlist for the computer chop saw and assembly diagrams to prefab the framing, and assemble it on site. 

A concrete slab floor is probably more common now, but is actually less quake (and flood) resistant.  A piled house can actually be knocked off it's piles, and be repaired. A solid concrete floor that cracks badly during a quake is impractical to repair.  So definitely different design considerations. Hard frosts and frozen ground isn't a risk here, so the deep foundations aren't needed, and piles only need to go deep enough to reach solid subsoil. Below grade basements are seldom used, as they tend to fill with water, even without any surface flooding (which is also common) 

[Ianab]

A house just appeared over night on the mail run. Yesterday it was in place, but 3ft off the ground, on jacks and cribbing. This morning it's down on the piles and they will be securing it in place. Complete 1960s (?) house was trucked 10 miles down the road from it's previous location. From what I can see the garage section on the left has been dropped on a concrete floor, the rest of the house is supported by new piles. Entry steps and any decks would be self supporting with their own posts in the ground. Attached to the house, but not relying on it for support. 

 Thing is the whole structure is a braced box, it doesn't rely on the foundations to hold it together. Although the bracing would be designed to meet up with the normal support points. But the whole box can be picked up and carried away.  

It's not designed to handle a winter ground freeze as that doesn't happen. So different design considerations depending on location. 


 

 

They have obviously picked the house site for the view... 

[Don P]

There really is no difference in the design methods or intent. The majority of your code reads the same or very similar to mine. Pier and pile foundations are prescriptive there with means and methods where it is engineered here. I prefer yours.

Section 5 calls out the need for bracing foundations and walls... the same continuous load path as here. 6.8 goes into prescriptive methods where my code requires engineering... those are the rules the op was requesting. Whether they would be acceptable to his jurisdiction would need to be checked.

 From what I see at a quick glance I would have no issues with a braced pile foundation built to those prescriptions. It looks like your minimum depth is a foot deeper than my frost depth.

[Ianab]

There really is no difference in the design methods or intent.

Earthquakes are notoriously difficult to engineer for, probably like tornadoes. There will  eventually  be a bigger event than you design for. One famous house in the  most recent Kaikoura quake was unknowingly built over a fault line. When the quake hit, the piles at one end of the house suddenly moved over 30 ft in relation to the other end. The whole house was spun 90deg and pulled from it's foundation.  The structure actually held up, and no one was injured although it was a wild ride, and  the house had to be written off due to the damage. But in that scenario, there wouldn't be any foundation that would resist that. So best you can hope for is that it doesn't pancake and hurt the occupants. 

 Issues they had with the Christchurch quakes was liquefaction of the ground due to the tremors. Ended up with "mud geysers" spraying mud and sand everywhere, and undermining the solid ring foundations that would then crack. A house on piles can be releveled and new piles put in if that happens. other minor fault lines only had a foot or 2 of movement, and the piled house was repairable. A solid foundation would have sheared in 1/2 and be a write off. 

So "best" design depends a lot on the expected local hazards.

[blackarrow]

I understand concerns about the stability of pier foundations. But, could the pier foundation be braced? They are independent elements anyway. I sure saw a lot of much bigger houses (at least in the USA) which are built on piers.

The pier foundations I had planned to build would be at least 40x40 cm and 1 m deep. That is the frost level in the region I build (Europe). If they could be so easily topped over, I do not know.

My concern was more about how to brace the building on the piers, so I effectively have a kind of box that will be a stable construction. And I wanted to do that without using OSB (when possible) and brace the building using diagonal braces and tongue&groove boards. I guess the shorted part of the building (3.2 m) will be more prone to instability, so there I would go with OSB anyway. But for the longer walls (8 m) maybe enough braces would be enough to keep the building from collapsing along that side.

At the same place where I will put this house, there are two sheds that are at least 30 years old with almost no foundation.



 



 

[Don P]

 Yes, review the sections of Ian's code I highlighted for an understanding of bracing the piers (they call piers  piles and call piles "driven piles").  Review the section on diagonal wood wall bracing in my code.

In both, a braced structure sits on a braced foundation, they are well connected to one another. Quantify load, provide resistance.

I assume there is some authority having jurisdiction there, what do your rules require, and do you have a link?

[blackarrow]

So, basically something like this (shorter sides covered with OSB, longer only with diagonals).


 

[jaciausa]

At the same place where I will put this house, there are two sheds that are at least 30 years old with almost no foundation.

30 years is nothing, timewise for a building to have achieved. This is an example of what you are trying to avoid. Currently I am dismantling a timber framed barn built 1920 in rural Iowa. This barn failed after all of this time because of the lack of adequate diagonal bracing and the foundation of limestone piers. It is a barn with basement that is exposed on two sides built on piles. The main oak posts are set on rock piers 16". There is no diagonal bracing and no feet (Footer). Very nice barn at one time. It failed because of what would be code violations today. I will post some pictures in new post when I can. The only good things about this are why codes are written and I am getting all of the barn and limestone foundation. It is an example of why buildings fail.

[Sod saw]

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Ian,  in your post # 10 you talked about earthquakes and your wish that the building not pancaking.

When I was younger, I remember my architect father describing a nursing home that he designed for around here in NY State.

NY is not known for its large quakes but we are on fault lines.

The nursing home had to be designed so that you could pick it up completely off the ground by one corner three feet in the air and drop it.  It needed to hold together.

Sounds like your neighbor house was well built.


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[BreezyHills]

  I find this thread very interesting; especially reading the viewpoint from different areas and the special requirements made necessary by local conditions.

  When I saw the title of this message thread, I was taken back to how the first houses that I helped construct were designed to be braced for stresses encountered while being moved after construction.
    In 1972 & 1973, I took an eleven month carpentry course at a vocational school in southwestern Missouri, USA.  During the course, we constructed two small frame houses (24'x48') on the paved parking area in front of the school building. Concrete blocks supported the sills of the foundation. 
  The houses were built to be auctioned at the end of the course, and then moved to their final location.  All the construction methods used were "old school" with 1"x10" boards set on a diagonal pattern for the outside walls' sheathing and the subfloor, and 1"x10" boards (in a straight line pattern) to deck the roof. (We used no plywood or osb or celotex panels in sheathing the outside walls or roof.)  The diagonal patterns of the wall sheeting were set in directions which let each wall help support the others.
  The houses were the most solid "stick framed" buildings that I have ever encountered, or helped build during my stint as a carpenter.  
  After a couple of years doing carpentry, I took a job in the oil fields of south Arkansas (more money), and stayed in the fields until I retired a couple of years ago.

  Now that I'm milling my own lumber, I think that I would most likely use that same method of sheathing my walls if I were to build a "stick framed" cabin. 

  Y'all please keep up the all the good discussions here on the forum. Everyone seems to be trying to be helpful. I'm learning a lot with every forum thread I read.  

Jim