siding

[slowpok]

I have a simple question.

My home has exterior plywoow siding, approx 1/4 thick.
some of the siding if not all needs replaced, so instead of
wood I was thinking of replacing with 4 ft x 8 ft hardie board.

or sould I stick with the exterior 4ft x 8 ft wood plywood.
one side sanded , pine because of stress factors?

My home is two stories high and has french/rustic look
with wood and trim siding.

I check with some local contractors. to install tyvex wrapping and install the 12" x 12 ' hardie board siding, but it's just beyon my budget.

please advise

[montytx]

Tyvex is code these days and hardie is pretty much standard. It also thends to cost about the same. How bout hardie 4x8 sheets. Somewhat easier to install cost a little less overall.

[slowpok]

Tyvex is code these days and hardie is pretty much standard. It also thends to cost about the same. How bout hardie 4x8 sheets. Somewhat easier to install cost a little less overall.

thanks for your feed back.

I under stand that tyvex is code, and standard.

my question is I will have to remove the old siding due to being rotten.
for replacement I would like to use 4' x 8' hardi board panel.
t0 reduce installation cost.

my question was? is hardie board as structurlly as strong at the same thickness in the 4 x8 panels?

thanks in advance

[Cole]

Yes it should be.^^

[VALENT]

hardi has got to be as good as 1/4 inch rotten plywood.

[Sweep]

I'm not aware of any building code requiring Tyvek. Where have you found that to be true?

[montytx]

Do a google for vapor retarders. Lots of cities states it is required and many say tyvek is a good choice.

[grumpydasmurf]

tyvek is code in my area.

So is a structural backing board. Often times this sheet plywood is used as the structural plywood... meaning there is apossibility of you take off the plywood you will see nothing but studs.

In my area if you take off siding and see the studs you have to install new plywood backing board before installing the new siding. You may be opening up a can of worms by taking off the existing siding, though I always prefer to take off the existing siding when ever within budget.

[Sweep]

Montytx, Tyvek is not a vapor retarder; it is, in fact, highly vapor permeable.

If Hardipank or any other cement based siding is used over Tyvek it must be back primed or there must be an airspace to avoid direct contact with Tyvek.

Grumpy, I am curious where Tyvek it required by code. I have done building facility surveys in the northeast, southeast and midwest (one just south of Chicago) and none of the applicable state codes required Tyvek as a siding underlayment although these codes may have changed recently. Since Tyvek can't legally be required by its trade name, and few of the many plastic underlayments are similar in permeability or construction, how is it specified in the code?

Here in MA, for the past 15 years, I have put a statement on my drawings forbidding the use of Tyvek or any other plastic underlayment in direct contact with cedar siding or cementitious stucco in order to avoid the unnecessary liability for water damage to structural sheathing due to the loss of water resistance of plastic underlayment when in contact with surfactants contained in these materials. About half of the contractors agree with me and the others are willing to comply. Only one was a problem but a couple of months ago I got a letter from an old client in CT that contained a newspaper clipping describing sheathing deterioration and mold problems in homes in their area and thanking me for making their contractor remove the Tyvek that he had applied to their house contrary to the contract drawings.

I am constantly in search of the best siding underlayment. Unfortunately, it isn't Tyvek or its imitators.

[montytx]

Sweep,
Im not going to argue with you. I am just relaying the fact that tyvek is the defacto standard these days on new houses and spec'd as code in many places. Here is a snip from dupont's site:

Construction
One of the most popular and widely known applications of Tyvek® is in the construction industry, where it is used to increase air and water resistance, helping to lower heating and cooling costs in buildings and providing better protection against water and moisture intrusion. The unique qualities of Tyvek® help stop air flow through wall cavities; help hold out bulk water and wind-driven rain; and allow moisture vapor to escape from inside walls. The result is a more comfortable, energy-efficient building with far fewer chances for damage from degradation effects.

So they obviously pitch and pitch it hard as a vapor retarder. We can start a whole other thread about whether wrapping a house in plastic is a good idea and all the terrible health consequences of doing so. I live in a 90 year old house with too many holes to count, but I know I won't have mold issues even if there is a leak.

:D

[Sweep]

There are three classes of "vapor retarders". Class I is so vapor impermeable (.1 perms or lower) that it is considered a "vapor barrier". The most permeable vapor retarder is Class III which allows a rating of between 1 and 10 perms. Tyvek is in the range of 58 perms so it cannot be considered a vapor retarder by any stretch of the imagination.

No building code could require the use of a specific product from a specific manufacturer such as Dupont's "Tyvek". There are so many house wraps with so many different materials and construction methods that it would be impossible to describe them in any coherent manner in the code. If a modern wall underlayment is required by code it would have to be defined by it's performance. Any performance requirement would have to incorporate all of the performance ratings of all of the plastic house wraps and they cover such a wide range that asphalt saturated felt would easily fall within the perameters and be acceptable to the code official.

Sorry for the lecture but the casual mis-use of technical terms, trade names and building code requirements gets under my skin because it can so easily mislead slowpok and others who come to this forum for information.

[bkrahmer]

If Hardipank or any other cement based siding is used over Tyvek it must be back primed or there must be an airspace to avoid direct contact with Tyvek. I just reviewed the Hardi-plank installation instructions again, and the word 'primed' is never mentioned. The instructions also show the planks being installed directly over tyvek. I'm not sure where you're coming up with that...

[Sweep]

You are looking in the wrong place. Hardi-plank (as well as wood siding manufacturers) take no responsibility for the design of the wall system. Photographs showing tyvek do not consitiute a recommendation. If you wish to use Tyvek you should first look at Dupont's installation instructions and then do an internet search for "surfactants tyvek", then ask Hardi-plank if their product contains surfactants.

Tyvek's instructions say (in very small print):

"Contamination of Tyvek®Weatherization Systems products and
building papers with building site chemicals that increase their wettability (e.g., surfactants) will adversely affect their water resistance and, therefore, their contribution to the overall water resistance of the wall system."

There are too many articles and papers on this subject to list them here. Some are:

http://hem.dis.anl.gov/eehem/01/010902.html

http://www.umass.edu/bmatwt/publications/articles/housewraps_feltpaper_weather_penetration_barriers. html

http://www.countryplans.com/bbs/messages/7288.html

Also look at Pathnet.org
http://www.pathnet.org/searchRes.asp?dl_sp=2&dl_typ=3&dl_s=keyword%3Dthe+guide&mc=sc_sp_top&id=6820&include=all

download the first article (pdf format) entitled "The Guide Vol 2 Ext Walls Rehab"
Go to "Infiltration Barriers" page 37 In the discussion of plastic house wraps it says:

DISADVANTAGES: Slightly more in initial cost than building felt. Availability of some products may be limited.
Inferior performance as a weather barrier compared with building felt. Nail penetrations in housewrap are not self-sealing, as they tend to be in felts. Housewraps are not selective vapor permeable membranes: mois-
ture vapor will pass through in both directions. As water-absorptive siding materials such as wood and brick veneer dry, moisture in vapor form can be forced through housewrap into sheathing and insulation. Less vapor-permeable building felt can better withstand reverse vapor migration. Some recent studies appear to indicate that surfactants, a class of substances found in wood, stucco, soap and detergents, can decrease the natural surface tension of water and allow it to pass through housewraps wetting the underlying materials.
According to anectdotal field observations, this process is most likely to occur in regions with heavy rainfall and when unprimed wood siding is placed in direct contact with the housewrap.

FURTHER READING

“Can Moisture Beat Housewrap?”, Ted Cushman, Ed., Journal of Light Construction, June 1997, p. 9.

“Sizing Up Housewraps,” Bruce Greenlaw, Fine Homebuilding, October/November 1994, No. 91, p. 42.

“Housewrap Manufacturers Prescribe New Details for Windows and Doors,” Energy Design Update, August 1998.

“Housewraps or Building Paper? No Perfect Answer,” Energy Design Update, July 1998.

“Housewrap vs. Felt,” Paul Fishett, Journal of Light Construction, November 1998.