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Question DetailsAsked on 8/28/2017

What is substrate?

We are putting siding on a historic bldg. in our town. With this status comes many restrictions. We are allowed to use only Hardie Board or Wood as siding materials. The building is currently made of stucco. We were told that the siding needs to be attached to the substrate. I'm confused by what this means and having difficulty getting a straight answer. Thanks!!!

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3 Answers


ARghhh - Angies List computer is taking out paragraph breaks AGAIN - so in reading, everytime you hit this ======= that is a paragraph break. ====== Interesting that it is currently stucco but only Hardieboard (a good classical historic building material by any standard ? - go figure) or wood is allowed for siding ? Does that mean the stucco was illegal - or that it is still legal but you want a siding alternative so they are prohibiting metal and vinyl siding, even though after painting the textured ones are indistinguishable from more than about 10 feet away ? =======
Oh - BTW - be sure if they mean hardiboard (a sheeet product) or hardiplank - a plank siding product. If the former than they are probably looking for a vertical siding that looks like board and batten or tongue and groove or rabbet-lap siding (like T1-11) or such ? ========
Anyway, the substrate is just the underlying solid surface it is attached to - so basically they are saying the siding cannot just levitate in open space, but has to be attached to the underlying material. In a building science sense, the "substrate" they are talking about is more likely the framing or original wall sheathing UNDER the stucco - so they may mean it cannot be attached just to the stucco but has to be attached to the underlying material, which a good contractor would not do anyway, to avoid blowoff in strong winds. ======== One can put hardiboard directly over breathable housewrap over firring strips over the stucco, creating an airspace between but not something I would prefer to do unless in a dry climate (though is common everywhere) - my preference would be to remove the stucco (because interior to a wall it can retain any moisture that gets to it) and apply the siding directly to the wall substrate - which would normally be plywood or plank in older houses or OSB or particle board or even hardboard or fiberboard in newer homes - which should be removed if not in VERY GOOD condition, and if hardboard or fiberboard I would say should be removed anyway as being a material which should never have been approved for framing use. ======== Since you are talking a historic building, I would contact the historic preservation permit person and ask if they are saying it has to just be attached through the stucco to the sheathing (if any) or wall framing, or if they are saying it has to be attached DIRECTLY to the sheathing or framing, meaning the stucco has to be removed. That may be what they mean, to avoid excessive wall thickness which would result in windows and doors being deeply recessed in the finished wall, which would result in a difference in appearance from the original I suspect that may be what they are getting at, which of course is a significant increase in cost (at least several dollars/SF and maybe as much as $5/sf more depending on type of and thickness of stucco - the cement-based ones can be EXPENSIVE to remove and are real heavy to dispose of). ========== Be sure top check on finishes allowed on the siding - both sheen and colors allowed - many historic areas prohibit the satin through gloss finishes, and of course strictly limit colors in most cases. ============ I would also confirm any restriction on siding width, and whether specific orientations are required - because hardi and wood can be horizontal or vertical in several different configurations such as different of lap siding, board and batten, tongue and groove, etc. ======== You don't want to get something in which they then do not like, Best to have your remodel architect do a rendering (or use a manufacturer website photo) or exact and color to be submitted for approval BEFORE committing to one product/color in a contract. Ditto on door/window treatment (especially if going over the stucco) because most historic preservation areas do not allow the exposed window flashings - generally requiring a more sophisticated profile brickmold or such around them. ========= Dealing with historic preservation offices can be an iffy thing - work with them and get them involved a bit and they are happier and a lot easier to deal wtih, but let them get too involved and you commonly get endless pie-in-the-sky design demands, but don't involve them enough or early on and they can get all huffy and become hard to work with just because they are being vindicative. One good reason using an architect with a lot of local historic district work experience and a good working relationship with them can save you a LOT of hassle and delays and possible rework. Plus if the architect comes up with design details that the historic preservation people then reject after it is up, you have potential coverage for the rework costs under his/her professional liability insurance policy if your contract with him/her specifies compliance of the design with all historic preservation requirements is part of his/her scope of work.

Answered 3 years ago by LCD


LCD... thank you so much for this info! I appreciate you taking the time to answer this question in such great detail. To answer your question about the stucco, I think it was constructed a long time ago before these are new restrictions. They definitely don't mean board and batten but the planks. I am concerned about asking about the substrate and opening another can of worms. The contractor is putting up wood that they will fasten the siding to and not remove the stucco. The wood strips are attached vertically to the stucco with screws. We now find out Hardie plank is too heavy to be attached to the wood strips. We are in over our heads! the only product that we can use that is not too heavy and approved is wood so we are getting primed red cedar. thx again!!!!

Answered 3 years ago by Photo416


OK - for hardiplank the battens (the vertical strips of wood over the stucco) wouldnormally be 1x3 or 5/4 x 3 - not just the usual firring strip material. This is where tying into the substrate comes in - the battens should be fastened to the studs (assuming you do not have 3/4" sheet substrate), then the siding to the battens or firring strips. That would be true for both hardi and wood siding.

This screwup on the firring trips, BTW, should NOT cost you more - contractor should have known that if he read the insructions from Hardi.

Remember, you need the proper wat vapor-permeable housewrap under the siding to prevent direct contact with the stucco, because the stucco will readily transmit (and indeed soak up) moisture from the siding. Remember, plank siding is NOT a waterproof siding - it is a "cl;adding" - sheds direct water hitting it, but a fair amount get in behind it in driving rain or windy conditions, so you need a vapor-permeable barrier like Tyvek Housewrap, or better for you use, Tyvek DrainWrap. You can find more on that in a couple of recent questions about siding and sheathing in the Home > Siding link under Browse Projects, at lower left.

Answered 3 years ago by LCD

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