| Author |
Message |
Anonymous
| | Posted on Wednesday, April 30, 2008 - 04:52 pm: |    |
Location: Florida Coastline
Exterior Wall: Concrete Masonry
Wall Coating: Modified Cement WP
Exterior Finish: Hardiplank
Question: How do you ensure imperfections in masonry wall will not telegraph to hardiplank? Which is better for this application: Galv metal Furring or PT Wood? |
Anonymous
| | Posted on Wednesday, April 30, 2008 - 05:13 pm: | |
I'd be concerned about wood absorbing a lot of moisture and holding it inside the wall.
If galvanized, should be heavy gauge material like that in 054000, have structural put it in their spec if possible, and probably at least G90 coating. Are such furrings available in alloy 316 stainless steel? It has better corrosion resistance, and with salt fog you might need it. |
Phil Kabza
Senior Member
Username: phil_kabza
Post Number: 313
Registered: 12-2002
| | Posted on Sunday, May 04, 2008 - 08:51 am: | |
Either galvanized steel (hot dipped G90) or PT wood furring can work. To minimize the "waviness" effect in lapped siding will require careful mechanics to plumb and string the furring and shim it when fastening so that its faces align - possible but time consuming.
Alternatives include using shingle style fiber cement panels that help hide the irregularities, or breaking up long horizontal runs of lapped siding with vertical elements.
You must use the alloy 316 fasteners anon mentions above; the more common 304 fasteners will corrode under paint at seaside. There's potential for bimetallic corrosion between the stainless steel and the galvanized steel furring that you should investigate - that potential causes me to favor the PT wood. As the PT wood will be able to release excess moisture through the breathable siding, I'm not as concerned as anon is about it absorbing moisture. |
Wayne Yancey
Senior Member
Username: wayne_yancey
Post Number: 43
Registered: 01-2008
| | Posted on Monday, May 05, 2008 - 10:39 am: | |
If PT wood is Borate, above grade and not directly exposed to liquid water, in the Pacific NW I specify: fasteners with double hot-dip zinc coating complying with ASTM A 153 (minimum coating G185) same as Maze Nail STORMGUARD, or Type 304 stainless steel. 316 stainless may be more appropriate in Florida.
If PT wood is waterborne alkaline copper quaternary (ACQ), exposed directly to weather, in the Pacific NW I specify: Type 304 stainless steel. Again, 316 stainless me be more appropriate in Florida.
Consider spacing the furring at 16" centers. Under certain lighting conditions, the shadow lines under each course will stand out like a pimple in the middle of your forehead. I agree with Phil regarding the shims and the shingle stile and board and batten alternatives for large fields of siding. Perhaps restrict the horizontal clapboards to smaller areas. |
Ron Beard CCS
Senior Member
Username: rm_beard_ccs
Post Number: 273
Registered: 10-2002
| | Posted on Monday, May 05, 2008 - 09:17 pm: | |
Relief from trapped moisture can be achieved by venting your cladding system at the top and bottom of the wall. Cor-a-Vent makes a variety of vents for various applications. For the wall described consider using Cor-a-Vent's S-400. |
John Regener, AIA, CCS, CCCA, CSI, SCIP
Senior Member
Username: john_regener
Post Number: 384
Registered: 04-2002
| | Posted on Tuesday, May 06, 2008 - 01:10 am: | |
Would it be possible when forming the concrete to simulate the appearance of simulated wood board siding? |
John Regener, AIA, CCS, CCCA, CSI, SCIP
Senior Member
Username: john_regener
Post Number: 385
Registered: 04-2002
| | Posted on Tuesday, May 06, 2008 - 01:18 am: | |
There are four high-rise apartment towers in Albany, California with terrific views of the Golden Gate. Custom masonry units were used that simulated shingles. The walls leaked badly, as did the roof, but there were strong shadow lines from the oversized shingle block units.
IMHO, the furring will need to have provisions for shimming (those plastic horseshoe shims?) to accommodate out-of-plumb masonry. From a recent project with wood board siding, prefinishing of the boards was very important in order to seal both the front and the back and also edges. Treated wood for furring will have inherent distortions that will need to be shimmed for trueness. |
Ralph Liebing, RA, CSI
Senior Member
Username: rliebing
Post Number: 837
Registered: 02-2003
| | Posted on Tuesday, May 06, 2008 - 06:58 am: | |
"....concrete to simulate the appearance of simulated wood board siding....."
Similar-- Can do and have done. Took wood panelling and sand blasted to remove soft wood leaving a "raised grain" pattern of the harder woods. We used these panels cut into strips to simulate board forming for some large plaster pilasters-- various widths; various lengths; less than the best joinery. Used thick white coat of plaster "laid" on metal lath and pressed the wood strips into it to form the wood board effect.
Would think same principle could be used but with the "strips" becoming the form liner for the walls. |
Wayne Yancey
Senior Member
Username: wayne_yancey
Post Number: 46
Registered: 01-2008
| | Posted on Tuesday, May 06, 2008 - 11:24 am: | |
PT wood strapping need not be thicker than 3/8" to facilitate drainage and drying. In the PNW and the lower mainland of BC, it is common to rip furring strips from 3/8" PT plywood. However, the field cuts require an application of preservative. PT dimension lumber is also common. Borate is the most common treatment for this type of strapping in my region.
An alternative to the Cor-a-Vent is insect screen wrapped and stapled around the furring top and bottom. Aluminum is prefered.
I echo John R's comment regarding back priming 6 sides of lap siding, even fiber cement. This requirement was encouraged by Dr. Joe Lstiburek during a recent 2 day seminar held at and by my firm. |
Anonymous
| | Posted on Sunday, May 11, 2008 - 10:08 am: | |
Fastening the siding directly to the block is a good option. We like using the ET&F Fastening Systems ASM-144-0125 pins shown on page 35 of the James Hardie NER405 Legacy Report: http://www.icc-es.org/reports/pdf_files/NES/NER405.pdf
Additional calculations are available from the manufacture for winds up to 150 mph. |
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