Can You Use Treated Lumber With A Metal Roof? Credit: discountlumberspokane.com Metal will not tolerate pressure treated wood. Because wood and copper are dissimilar metals, they rust due to chemical reactions.
What is the chemical used to treat wood?
What happens when electrons move away from an anode?
How does metal corrode?
Can you use untreated purlins on a metal roof?
Who is Paul Fisette?
What should I put between treated wood and metal?
The Metal Construction Association suggests that copper-containing preservative-treated lumber should ideally be separated from metal roof or wall panels and accessory materials using a polymeric membrane material between the metal panel and the wood substrate.
Can you put galvanized metal on pressure treated wood?
What metals and protective coatings does the Treated Wood Industry recommend for use with these products? Hot-dip galvanized or stainless steel fasteners, anchors and hardware are recommended by the Preservative Treated Wood Industry for use with treated wood.
Will pressure treated wood corrode metal?
Using pressure-treated lumber (PT) in home construction is very effective in reducing wood destroying insect activity, but it has the adverse effect of causing corrosion on most hardware and fasteners.
Does treated wood react with metal?
ACQ treated lumber is reportedly more corrosive to steel and coated steel than CCA treated lumber 3. This has raised concerns regarding the corrosion of Structural Galvanized Steel Sheets typically used in bracketry or similar hardware, Architectural Steel Sheets used in roofing and siding product, and fasteners.
What metals are safe for pressure treated wood?
NOTE: The manufacturers of ACQ-treated lumber recommend using stainless steel fasteners with this lumber. Metal components made of aluminum will corrode when in contact with ACQ-treated lumber.
What is the best thing to put on pressure treated wood?
For optimum results, first treat the wood with a paintable water-repellent sealer/preservative. After the floor dries, a primer and two topcoats of porch and deck enamel should be applied. Porch enamel is especially formulated to resist abrasion and wear.
Does aluminum react to pressure treated lumber?
The Short Answer: A Barrier Membrane between the aluminum and pressure treated plywood. As long as the aluminum is not directly touching the pressure treated plywood, you will not experience any corrosion or reaction between the two.
Do galvanized nails react to pressure treated wood?
However, the zinc in galvanized nails reacts chemically with cedar and redwood. Nail manufacturers recommend that you go with aluminum or stainless steel fasteners when you're using either of these woods—and whenever you're using pressure-treated wood. (The preservatives incorporate salts that react with the zinc.)
What should I put between treated wood and aluminum?
Alternately, a rubber or plastic mat or sheet can be installed between the treated wood and aluminum to eliminate contact points.
Can galvanized screws be used in treated lumber?
The treated wood industry specifies or recommends stainless steel and hot-dip galvanized products for use with pressure treated wood.
Does Galvanised steel react with treated pine?
When a galvanised fastener is used in treated pine, its zinc content is targeted by the copper oxide; it is then depleted of its electrons, and then accelerates into corrosion. The process is known as 'oxidation' – also known as 'rusting'.
Is it OK for pressure treated wood to touch the ground?
All treated wood is now “ground contact”. “Ground contact” has a high chemical retention level and can be placed directly on or in the ground. This provides better protection against rot and decay.
Do galvanized nails react to pressure-treated wood?
However, the zinc in galvanized nails reacts chemically with cedar and redwood. Nail manufacturers recommend that you go with aluminum or stainless steel fasteners when you're using either of these woods—and whenever you're using pressure-treated wood. (The preservatives incorporate salts that react with the zinc.)
Does Galvanised steel react with treated timber?
Testing results clearly showed that galvanised and mild steel fasteners embedded into timbers treated with ACQ and CuAz preservatives, particularly at the H4 level, are significantly more degraded through corrosion than corresponding items in CCA treated timbers.
Can you use galvanized nails on pressure-treated lumber?
The manufacturers of ACQ, CA, ACZA and CCA and the treated wood industry are all recommending hot-dipped galvanized nails and stainless steel nails and screws with their treated wood products. Furthermore, they specify that the fasteners meet the ASTM A-153 specification for hot-dipped galvanizing.
Can you use galvanized flashing with pressure-treated lumber?
Never use galvanized steel or aluminum flashing in contact with an ACQ pressure-treated wood ledger board because it will corrode. Vinyl flashing is the least expensive option, but it may not work as well in areas with extreme temperature fluctuations.
When To Use Pressure Treated Lumber And When To Avoid It
When it comes to choosing the right lumber for a specific home project, the decision begins with the type of wood. All lumber, from the common 2x4 to specialty marine plywood, is either pressure treated or not.
treated wood and galvanized roof - Metal Roofing
jim smith: "I've just put a plain, galvanized (shiny, no paint or ..." - treated wood and galvanized roof (7/22/2011) within the Installation discussion of the residential metal roofing forum
Can you use pressure-treated wood for roof rafters? - Quora
Answer (1 of 4): You could but I personally wouldn’t for the same reason bob Busch cited. If you go down to your local lumber yard, in my case Home Dumpo, and just hold up the various grades of lumber you probably can spot the differences. The Pressure Treated material, (hereafter PT), feels real...
Pressure treated furring strips - any effect - Metal Roofing
My contractor is installing typical painted metal sheets over an existing 5v metal roof by furring out with pressure treated 1x4's. One maker of a metal roofover system advised that the chemicals in the treated wood would "eat" the metal.
FAQ: Pressure-Treated Wood with Barrier Membranes
Grace Construction Products, a worldwide manufacturer of barrier membrane technologies, presented Simpson Strong-Tie with its corrosion testing research, which evaluated the performance of applying a barrier membrane between a connector and preservative-treated wood.
How does pressure-treated lumber interact with metal?
When two opposing metals are placed together, a process called electrolysis happens, in which the harder metal attacks and erodes the softer metal. Pressure-treated lumber is often treated with one of two chemicals: copper azole (CA-C) or alkaline copper quaternary (ACQ), both of which contain copper (a harder metal). If the treated wood is situated next to flashing or fasteners made out of a metal softer than copper—like aluminum—the copper in the treated wood will attack the softer metal.
What happens when two metals are placed together?
When two opposing metals are placed together, a process called electrolysis happens, in which the harder metal attacks and erodes the softer metal. Pressure-treated lumber is often treated with one of two chemicals: copper azole (CA-C) or alkaline copper quaternary (ACQ), both of which contain copper (a harder metal).
What metal is used to protect lumber from flashing?
To prevent treated lumber from attacking flashing and fasteners, you’ll need to make sure they're made with a harder metal than copper. Hot-dip galvanized or triple-zinc coated metals are great options. And remember: Because of its lower copper content, CA-C is a more user-friendly treatment material.
How much chemical treatment is required for ACQ?
CA-C coating requires 0.15 pounds of chemical treatment per cubic foot to achieve ground contact (treated to the point that the wood can withstand rot and decay even if it’s touching the ground or leaves), whereas ACQ requires 0.4 pounds of chemical treatment per cubic foot. Since ACQ has more copper, it’s more corrosive than CA-C.
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Can I put underlayment over shingles?
First of all, I always suggest underlayment over the old shingles regardless. From there, some products can be installed on battens or direct to deck. Some must be installed on battens. And yet some other products must be installed on solid decking. The best choice is to determine the product you want to use and then ensure it is installed according to specifications.
Can you put battens over a new roof?
You should be able to do that. Make sure that the new roof is approved for installation over battens like that.
Can metal roofs be installed over battens?
Please realize that not all metal roofs can be installed over battens and only a very few MUST go over battens. You are correct on the treated lumber thing. if you go with battens you will need to go with raw untreated lumber or painted lumber.
Is treated lumber corrosive?
The chemicals in treated lumber can be corrosive and damaging. If you have any way of sealing them beyond just the stain, that would be good.
Can flashing metal be pulled off PT lumber?
I have seen plenty of flashing metals pulled off PT lumber and the amount of deterioration is significant. Be careful and use compatible components.
Is it safe to use natural lumber without chemical treatment?
If it is natural lumber without chemical treatment it should be okay.
Why can't I put plastic on wood sheathing?
I would not install plastic on the sheathing because it’s a vapor barrier. If the temperature of the plastic drops below the dew point, then water can form on the underside of the plastic and cause the wood sheathing to rot.
How wide should a gap be for a roof?
Be sure you create a gap of at least 1/4 inch in at least two places as you install the pieces of strapping on each row. I know you’ll be tempted to use one long 2-by-4 as you march up the roof since the roof is not that wide.
Why is felt paper used in water vapor?
Felt paper, because of the way it overlaps, tends to provide a pathway for water vapor to pass between the overlap joints. Giant sheets of plastic don’t offer this escape route.
What happens when a metal roof cools down?
When the metal roof cools down at night and its temperature falls below the dew point of the air that’s contacting it, the water in the air turns to liquid. You see this happen on just about any warm day, or even inside your home in the winter, when you have a cold beverage glass or can sitting out. Within minutes, beads of water form on the cold vessel and begin to drip down to the table or countertop.
Can water vapor float through a metal roof?
When you install a metal roof over a finished living space in just about any place other than the Atacama Desert (where it’s not rained for decades), water vapor can and will float up through the ceiling and find its way to the underside of the metal roof.
Can you put felt paper on a metal roof?
Within minutes, beads of water form on the cold vessel and begin to drip down to the table or countertop. Most metal roof companies recommend installing felt paper on roof sheathing before you install the metal roofing. The asphalt in the felt paper is waterproof and does a great job of protecting the untreated wood roof sheathing.
Can condensation be on metal roof?
You’re correct that condensation can be a huge problem with metal roofing. Over the years I’ve answered many inquiries from people who believe they have a roof leak, whereas the problem is condensation forming on the underside of their metal roof. This water eventually runs down the underside of the roof and finds its way inside the home.
How Long Will Metal Roofing Last on Plywood?
If you are installing metal roofing onto plywood, it is even more imperative that you have a solid base to place the metal roofing on.
How thick should plywood be for metal roofing?
The plywood or OSB you use for a base underneath your metal roofing should be at least 7/16 inch thick. This thickness will ensure that the wood is sturdy enough to hold the screws in place and support the metal roofing. (Source: International Association of Home Inspectors ). Install a felt moisture barrier.
Why is slip sheet important?
The slip sheet is also an important layer. This smooth, industrial paper is laid on top of the felt to protect the felt from the metal roofing material. The metal can heat up from exposure to the sun and adhere to the tar-infused felt sheeting.
Why replace rotten wood?
Replacing rotten wood is critical because dry rot will spread. Adjacent areas of healthy plywood may eventually become rotten, and then the screws you have placed there will not hold. Warped wood should also be replaced. Warping signifies that the wood is prone to rot and will prevent you from laying the metal roofing flat. Wind will be able to get underneath the roofing and pull it off your roof.
Why do you need a slip sheet on a metal roof?
You may also want to install a slip sheet to protect the felt sheet from potential damage caused by the metal roofing. If you install your metal roofing directly on plywood without the protective layers, you greatly increase the odds of the roof leaking. You also run the risk of premature wood rot, as the felt sheet provides a layer ...
How long does it take to install metal roofing?
If you are installing the metal roofing yourself, you can expect a significant time investment. Depending on the size of the roof, you can easily spend a week or more on the installation. Weather conditions could affect this time, as well as other factors like the slope of the roof.
Why do you tie yourself off when you work on a metal roof?
This goes double for a metal roof because the metal surface is more slippery than shingles which have granules which prevent slipping.
What are the preservatives used in wood?
At that time, the other primary preservatives in use were creosote, a coal/tar derivative, and pentachlorophenol (penta), an oil-based preservative.
Can copper treated lumber be used on metal?
The most effective way to avoid corrosion is to ensure that the treated lumber used is either manufactured using the newer carbon-based preservatives (Ecolife® or PTI), micronized copper preservative (MCA or MCO) treatment or that there is a separation between the metal roof or wall panel and the pressure (preservative) treated wood with some type of barrier material. (The preservative-treated lumber manufacturer should always be contacted to verify that the material may be used in contact with the intended metal components.)
What chemicals are used to treat wood?
The two most popular chemicals for wood pressure treatment are alkaline copper quaternary (ACQ) and copper azole (CA). These two chemicals are active corrosion materials. Two corrosion protection systems are recommended for use with these chemicals, hot-dip galvanized steel and stainless steel. All other systems do not have enough corrosion ...
What is pressure treated wood used for?
Authored by Dr. Tom Langill. Pressure treated wood is often used for construction areas that will be exposed to the weather or in high moisture areas. The chemicals used to treat this wood have been revised in 2003 to remove some of the potential harmful elements in the pressure treatment.
How long do metal roofs last?
Modern metal roofs are expected to last 30 years or longer. When the metal is eventually replaced, roofs without plywood underlayment require the insulation to be replaced or repaired because it is attached to the metal.
Can plywood be used on metal roofing?
Fastening to Purlins. For many applications, a layer of plywood underneath your metal roofing is an unnecessary expense. Metal roofing panels rated for "architectural use" attached to purlins (horizontal pieces of wood or metal fastened to roofing trusses) are structurally sound when installed according to your roofing manufacturer's instructions ...
Can metal roofing be attached to plywood?
Although it may seem counterintuitive, metal roofing can be attached directly to your building's roofing structure without the need and expense of plywood sheeting. As long as the interior of your roof is protected from moisture accumulation, underlayment is not required, though homeowners planning to insulate their house heavily may choose ...
Where is Erik Johnson?
Based in Colorado, Erik Johnson has been writing professionally since 1996 and has worked in real estate, management and technical fields. Recipient of the 3M Richard G. Drew Recognition of Creativity, Johnson is the author of three books.
Can you attach a metal roof to a purlin?
Preventing Condensation. In a barn, shop or other outbuilding, you can attach your metal roof directly to the purlins. In a residential application, however, condensation is a concern. Moisture can collect on the inside of your metal roof whenever warm, moist air inside your building meets the cold metal of your roof.
What is the chemical used to treat wood?
Most pressure-treated wood is treated with chromated copper arsenate. The metal present in the treatment chemical (copper) is dissimilar to the metal roofing (steel). I would be concerned that galvanic corrosion could degrade the metal roofing or fasteners. Galvanic corrosion occurs when electrons move away from an anode toward a cathode.
What happens when electrons move away from an anode?
Galvanic corrosion occurs when electrons move away from an anode toward a cathode. This electron transfer causes the anode to degrade, while the cathode stays intact. If you remove one of the three components (the anode, cathode or electrolyte), you can prevent corrosion.
How does metal corrode?
A metal can corrode when minuscule amounts of electricity travel through an electrolyte connecting dissimilar metals. Water is an electrolyte. Since condensation is very likely to collect on the underside of metal roofing, you have an electrical conduit waiting to be plugged in. Most pressure-treated wood is treated with chromated copper arsenate. ...
Can you use untreated purlins on a metal roof?
The easiest way to avoid this potential problem is to use untreated purlins. If you insist on using pressure-treated purlins — for example, for termite protection — you could paint the purlins or the back of the roofing to break the electrical connection. Perhaps installing a plastic spacer or a strip of self-adhering roofing membrane between the metal and pressure-treated purlins would be a more practical way to separate the dissimilar metals.
Who is Paul Fisette?
About the Author. Paul Fisette. Paul Fisette is a wood technologist and former director of the Building Materials Technology and Management program at the University of Massachussets in Amherst, Mass. Advertisement.
