I'm looking at replacing a couple of leaky windows in a south-facing vaulted ceiling (clerestory windows) of my house. The siding is rotten as well, which means I should take it off, probably replacing it with hardiboard or hardiplank. I'm not sure what the current best practice is for the layers under the exterior, though.

The outside layer is plywood. Under the plywood is a foam board product with silver cladding, which as far as I can tell is directly attached to the frame of the house. Inside the wall is batt insulation and then drywall.

That seems... skimpy to me. Is this proper for this climate, and if not, what should actually be there? A layer of OSB and housewrap with the siding on top of it? Considering that this is an exposed south facing location, what would be best to replace it with if I'm going to be replacing the siding anyway?

That should be fine with what you got-OSB Sheathing, Tyvek then siding. Hardieboard is a good product but it's very brittle, expensive, difficult to work with and is very pourous (you will repaint in 10 years). I sell siding for a living-I recomend SmartSide strand substrate. It's the only 5 (labor and material cost)50 year tranferable warranty across the trim soffit fascia lap lines, on the market and holds paint better, stronger and looks better than Hardie. Same stuff Pulte, Bloomfield, DR Horton Meritage, History Maker, Darling use to name a few. Hardie went to 30 year warranty on their lap (formerly 50 years), 25 on thier panel, and 10 year on the hardietrim. and the fire rating? SmartSide has the SAME one hour fire rating as Hardie. Yes it will burn but unless you have steel framing it's irrelevant. Fires are started internally anyways. we have changed a lot of city codes into adding "Engineered" Wood siding along with cement siding in deeds.

Superspeck, according to code, you don't need OSB sheathing with wood or fiber cement siding. You do need it with vinyl siding.

Therealfan, I am planning on replacing some siding soon. I was going to use hardiepanel. I didn't consider using a wood product because of the rot resistance that hardie siding provides. How does the smartside product do in that regard? Do you sell both products or just the smartside? One thing I do like about the smartside is that it would be much easier to cut and install as I wouldn't have to get a separate blade/respirator to cut it. Plus it is much lighter.

James,

If you are DIY, then Smart Panel is MUCH easier to work with. In other words, Hardie panel close to 80 lbs vs. SmartSide Panel that is around 45 lbs (nominal thickness is same). It's available in the 3/8 and 7/16 and the best part about it? you can nail direct to stud, you don't have to have a backing but I am assuming you would have backing because it's twice as strong as cement (cement contains wood fiber for any strength that it does have)

Hardie-layered cement
Certainteed-made in a liquid form of cement
Cemplank-same as hardie but has continuous pattern (ex. knot hole, knot hole, knot hole)
Maxiplank-from Mexico-awful product 10 yr warranty (all cement is not created equal)

The 3/8 Smart Panel is a few backs cheaper a panel as well and is the #1 selling panel at Depot or Lowes. The most common perception is still out there---it's wood. however, it's formulated with Zinc Borate that's actually impregnated into the wood fiber strand. This prevents the natural wood decay cycle, it's basically a simple salt that kills termites as well as rot. It's a non toxic salt-similar formulation in Visine and other household products. It's also got the strongest deepest embossed cedar grain on the market. Only require one coat of paint and if you countersink a nail? (every siding has countersunk nails), you can simply caulk it and you are covered. 99% of homes with Hardie are not covered by warranty (one reason Hardie Lap went from 50 year to 30 year). They have lawsuits all over Australia right now that they are fighting.

I wanted to have a thread strickly on perception vs. reality in siding because 10 years ago, 3 big builders in Houston used SmartSide, now? over 25 production builders. Hardie has most of the lap but builders and homeowners have turned the page so to speak. Same battle with value added OSB vs. Plywood. Lots of old dogs remember "chip board" wafer wood etc....Everything is engineered today. In fact my company is the reason Hardie took advantage of Texas. in the early 90's we made a "Billion Dollar Class Action Lawsuit" (Innerseal) that was poorly constructed. They fixed the major glich and since SS has been on the market (1996), there's been over 6 billion feet sold in the US.

www.lpsmartside.com is our website.

"Engineered Wood" siding is placed into most City codes along with cementacious siding(not little elm, city of Arlington just approved it) DFW is the only place we fight this most of the time. HOU and SA there's never any issues.

Best part of all is LP SmartSide is around 15-20% less than James Hardie.

Hardie ALWAYS has to have a backing. If it didn't you could litterally punch a hole with your fist into the product.