Cement-Fiber house siding properties

[oldestguy]

Hi:

Being new to this forum, this may be an old question.

I'm thinking of siding a new house with cement-fiber siding. The house will have full insulation (closed cell foam) surrounding and under the basement foundation. Local codes say no earth backfill should be nearer to house siding than 8 inches to keep moisture from rotting the wood frame and for termite protection. However, this plastic foam does not like sunlight.

Covering that foam insulation used to be done with the old asbestos cement board and it worked. I'd like to start a siding job at the backfill elevation and continue up the walls, assuming the cement-fiber siding will not take on water and wick it up to the wood, etc.

Are there tests for moisture absorption or is this so cut and dried these days that there is "no problem"?

 

[Ron]

OG...cement fiber products such as Hardie Board and others of similar manufacture, will absorb and wick moisture. I don't know of any product in this class of materials that will not wick moisture, except perhaps the composites using recycled plastic.

 

[boo1]

Consider parged walls, Type "N" mortar or pre-mixed stucco can be used. Or you can mix your own combination of sand, lime and cement. A sand mixture of 1 part cement with 3 parts sand and 1/4 part lime. Dirt and debris should be cleared away from the foundation to a depth of 4"-6" below finish grade before parging. Keep moist for 7 days after application.

Dont forget about termite paths.

 

[hokie66]

The fibre cement boards should do the job of protecting the insulation, but you should have a separation between these boards and the siding above.

 

[oldestguy]

boo1: Parged walls covering has been used by my builder, but he tells me his experience is that folks with weed whips will tear it off to some extent.

Some years back a place I had built with cement-asbestos boards worked well and when I sold it no one complained. I wonder it some of that board is still sitting around in a warehouse where I can get some?? Hey, I'm still alive having be brought up in an old house with asbestos wrapped heating ducts.

As to a break for wicking, maybe flashing in a "Z" shape would work, top part under the first course of siding.

Any of this is better than running the earth right up to the siding, like I see so common now.

 

[Ron]

OG..yes, a Z-flashing will work. Typically, the siding should not start closer than about 4 inches from the ground.

Also keep in mind that the cementitious board products made today are not nearly as tough or durable as the old "Transite" panels of cement-asbestos. Weed whackers will cut into the newer materials.

While wicking of these materials is less than a composite wood product, it can occur, but usually only if exposed to very high moisture.

What about stucco?