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Question DetailsAsked on 3/9/2017

I want to put corrugated tin on hardyboard

The house has masonite siding on it. I want to put tin over the siding vertcally. do I need to take the siding off first or can I go over it?

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2 Answers


Seems to be a bit of confusion on terms here - Masonite is a company brandname, not a specific product for quite some decades as I recall - the company is actually more a door than a wood product company today. But the term Masonite for a siding product is commonly understood to refer to a tempered hardboard product (basically sawdust and glue steamed in a high-pressure press to form a board product with one shiny surface, the stuff peg board sheet is commonly made of) and was heavily used in the 60's through about 80's (and locally long after that, and even today in a few areas where the building departments don't care about homeowner's buying a lemon), even though it was a grossly unsuitable product for exterior use because it is water-shedding at best (not water resistant or proof) and picks up water and retains water and then swells and falls apart like cardboard.

This is NOT the same as HardiBoard (your Hardyboard), which is a highly water resistant concrete product (basically the same material as HardiPlank concrete siding) and which could certainly be left under a metal siding - though firring strips to create an airgap (not necessarily thick enough to hold the metal siding screws as would be needed over bare studs) and a water barrier would still generally be used over it so any water getting through the siding does not also wick into and soak through the concrete board into the wall, but will instead run off along the water barrier to the ground.

I definitely would NOT leave masonite under any type of siding given a choice, but that is personal preference - many siding contractors will leave it if in decent condition and not falling apart (and some even then), and it is still used under stucco wall coverings in some areas. However, since properly done there would still need to be firring strips to fasten the siding to, I would go to the minimal added cost of removing it.

Here is a previous similar question FYI - along with some other links to related questions and answers:

Now for the metal siding - you said tin siding which you would be hard pressed to buy today, at least in the US - so I don't know if you mean aluminumm or steel sheet siding (similar to sheet metal roofing and available in several designs and many colors) or corrugated galvanized steel like what quonset huts are made of, and as commonly used on sheds and barn roofs and such.

Though using galvanized corrugated metal for house siding would be pretty much guaranteed to tick off any neighbors within miles for appearance and property value damage reasons, and unless a backwoods cabin or such would probably make it nearly unsaleable come move time, for either type I would remove the masonite and put on the appropriate substrate for your area (below), then water shield (a water-shedding housewrap made by DuPont under the Tyvek name and others), then the siding.

The substrate might be just 1x2 or 1x3 firring strips or strip metal firring stock over the studs to screw the siding onto if in an area with negligable heating or cooling demand (and if code does not require a sheet wood underlayment for structural reasons as many do), a wood sheet underlayment like plywood (or particle board or OSB, shudder) and maybe a folded sheet or roll-out insulation in mild areas with some but not serious HVAC loads then firring strips, or a foam board or foamed-in-place insulation overlain by firring strips in serious heating and/or cooling" in most US climates.

A true vapor barrier (truly air and watertight) is used under the siding only in the few areas where the vapor barrier is put on exterior to the wall rather than under the interior finish because the major threat is from outside wind-blown rain or constant exterior high humidty rather than inside moisture, like a few high-wind wet areas of the Northeast (Maine coast and some island areas for example) and a few extremely wet or tropical areas like parts of the Pacific Northwest coast, Olympic Peninsula and BC coastal and island areas and the warmer parts of Southeast Alaska and the Aleutian Islands, for instance - and most of Hawaii and Puerto Rico. Elsewhere a vapor retarder which prevents large volume moisture transfer and promotes runoff on its outside surface is generally used, though in some areas - like some Southeast and Gulf Coast and tropical areas a water barrier (vapor retarder) is not recommended, depending on details of the wall constructiuon and layering and materials used, and any built-in in-wall ventilation.

Personally, if I were doing it, I would strip the masonite and after repairing any wall insulation issues and sealing electrical boxes and top plate penetrations and such (something generally not though of when replacing siding), I would put the code required wood underlayment over the studs - commonly 15/32 treated sheathing in plywood or OSB (shudder again) and/or solid foam board depending on climate, then back-slotted firring strips (the back-slotting to let any water pass down the surface is commonly omitted by all but the best contractors), then the water retarder, then the siding with gasketed seams.

[Note - some siding manufacturers recommend the water barrier go UNDER rather than over the firring strips, especially with steell siding, to prevent a damp contact surface on the back side. If the water barrier is UNDER the firring strips than you definitely need to use back-slotted firring strips to keep then from damming up any water running down the surface of the water barrier - and the firring strips should be treated wood or metal siding flat purlin strip because they will get damp and/or wet at times, if not from siding leakage then from condensation on the back of the siding].

Answered 3 years ago by LCD



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