External Timber clad

[Aleeex]

Hi

when designing a small residential property with external timber wall clad and masonry, should you consider the external wall against lateral forces?

 

[jayrod12]

Perhaps a sketch of the wall construction, and how is the roof supported?

I assume you mean wind against the wall, not shear wall forces. If so, how is the timber cladding attached to the wall?

 

[Aleeex]

The roof supported on the wall. This is sketch of the wall construction.

 

[jayrod12]

Then you need to design the cladding to span between the horizontal battens, the horizontal battens to span between the vertical battens which are directly applying the load to the block wall. So the block wall needs to be designed for the full wind load, applied to it by the vertical battens. This is in addition to the loads applied to the wall from the framing above. Use the appropriate load combinations for your area of practice.

 

[Aleeex]

Thank you that is very helpful.

One more thing, when I need to design the block wall, shall I use the full length of the building 7+4=11m or just till where is internal stud wall intersection 7m?

 

[jayrod12]

Usually masonry walls would span vertically between framing levels.

 

[Aleeex]

Yes but when I check the wall , I need the height and length of the panel. In my case, I got 3 meter height, but was not sure what is the length shall I check for. The wall was failing even for 7 meter length, I thick I should add bedding reinforcement.

 

[jayrod12]

Where I practice the length doesnt matter, except for spacing of joints, provided the wall can span vertically.

We also always have joint reinforcement in every second mortar bed.

 

[Aleeex]

If I design the wall for 1 meter length would pass easily.

 

[jayrod12]

I guess a small clarification. The length of the wall matter for shear wall design.

But yes, generally speaking my masonry load bearing walls are designed on a per meter of length for out of plane wind loads plus axial loads.

 

[BAretired]

Yes but when I check the wall , I need the height and length of the panel. In my case, I got 3 meter height, but was not sure what is the length shall I check for. The wall was failing even for 7 meter length, I thick I should add bedding reinforcement.

You must be checking the masonry wall as a two way slab. That can only be justified if the stud wall is connected to the masonry wall to resist tension as well as compression. I don't recommend it because stud walls may be moved at the whim of the owner, so better to design the masonry to span vertically and forget about the horizontal span. Use 190 masonry if necessary.

As a matter of interest, you seem to have a lot of battens in your wall section. Is that standard construction in your locale? I have never seen it before. The 10x50 vertical strips don't appear to have any function (that I can see). Why not connect the 50x50 battens directly to the masonry? If the timber cladding is spanning vertically, use horizontal battens, otherwise use vertical battens, but you are using two sets of battens.

BA

 

[jayrod12]

BA,

Double crossing battens (we call it strapping locally) is becoming more common with the whole "minimize cold strike" stuff we're dealing with nowadays. On vertically applied cladding we provide vertical strapping and then horizontal. If you provide just horizontal strapping, then you're giving multiple places for water to pool if when it does get behind the cladding.

 

[Aleeex]

If I deign the masonry to span only vertically, the wall is never going to pass, it will terribly fail. however, when designing the wall 2 ways, it will not fail. I believe the only matter here is the shear , vertical load.

 

[jayrod12]

Are you sure? I get that 140 block works just fine for what I would consider typical loading?

What magnitude of axial and wind loads do you have in the location of the project?

 

[Aleeex]

5 kN/m dead load , 5 kN/m Imposed load and 1.4 KPa wind load. If I design the wall spanning two way, 1 meter long all edges supported, the wall will pass and the utilization is low, however, if I only support the wall top and bottom, the load span only one way, the wall will fail on horizontal loading.

 

[jayrod12]

When I run it using 15 MPa 140mm blocks, I get it passes at around 67% utilization with a 15m bar @ 1200 o/c. Using the same loading you gave but designed to my local code (CSA). And to be honest, the CSA numbers are far lower than other places in most cases, so I'm surprised you can't get it to work.

 

[Aleeex]

What is 15m bar @ 1200 o/c? what does that mean?

The utilization I have got now is 0.4 but that for 2 ways spans. As I mentioned it will fail if I design the wall supported top and bottom but that is not the case.

Can you send me copy of your calcs?

 

[jayrod12]

Different locations different reinforcing call offs. That is a 200mm² reinforcing bar spaced at 1200 mm o/c. So every sixth core is reinforced and grouted.

Also, different codes, different calculations. Our local code here wouldn't allow unreinforced load bearing walls in 140mm blocks.

 

[Aleeex]

The wall passed without wires, so it is not needed.

 

[BAretired]

The wall passed without wires, so it is not needed.

Really? What has changed?



BA