Yes, roof rafters should be pressure-treated because pressure-treated lumber
Lumber
Lumber or timber is a type of wood that has been processed into beams and planks, a stage in the process of wood production. Lumber is mainly used for structural purposes but has many other uses as well.
Full Answer
What is the best plywood for a roof?
What is the stress rating of a timber frame?
What is the roof joist called?
What is the structural member that runs vertically from a wall, valley rafter or hip to a hip?
What is the most common wood species?
Do rafters extend beyond the top of a wall?
Can PT lumber warp?
See 4 more
About this website
Can you use pressure treated wood for roofing?
CCA-treated lumber for commercial use is available from treated wood manufacturers. CCA-treated wood had been used successfully since the early 1930s and became accepted as a reliable performer when used as blocking and nailers in roof assemblies.
Should I use pressure treated wood for rafters?
As long as there's a good chance that moisture can reach the wood, it should be pressure treated. This is why the International Building Code requires that siding and structural lumber used for the last six inches of the structure above the ground is pressure treated.
What kind of wood do you use for roof rafters?
Many rafter span charts delineate between rafters using SYP (southern yellow pine) versus SPF (spruce, fir, pine) lumber. SYP is one of the densest softwoods, so it is strong but more difficult to cut and nail into. SPF is light and easier to use when framing.
Can you use treated lumber as trusses?
Preservative treated lumber is another common material used in trusses. Again, different brands and types have different reduction values. When certain types of chemicals are used, plates must be coated with approved materials to prevent corrosion. Alternatively, stainless steel plates may be used.
What should be used for roof rafters?
Rafter boards that create the slope of the roof are typically wider than ones used to create trusses. While 2x4s are most common in trusses, 2x8s, 2x10s, and 2x12s are most common in rafters. In a finished space, insulation is placed between the rafter boards and drywall.
Do termites eat pressure treated wood?
Even pressure-treated wood and naturally durable woods are susceptible to termite damage and infestations. That's because termites can tunnel over treated wood easily to get to untreated wood or other cellulose-containing substances in a home.
How far can a 2x6 roof rafter span?
Maximum allowable span for a 2×6 rafter:- the maximum allowable span for 2×6 rafter is 16 feet 5 inches when spaced 12 inches apart from centre, 14 feet 8 inches at 16″ OC & 12 feet 8 inches at 24″ OC with best quality No.
How far apart should 2x6 rafters be?
A 2×6 spaced 16 inches apart can span a maximum distance of 13 feet 5 inches when used as a rafter, 10 feet 9 inches when used as a joist, and 6 feet 11 inches when used as a deck beam to support joists with a 6-foot span.
What size rafters do I need for a 12 foot span?
As per general rules and guideline, for 10 -12 foot span, generally you need 2″×6″ size of rafter, for 15 -16 foot span, you need 2″×8″ rafter, for 18 – 20 foot span, you need 2″×10″ rafter & for 24 foot span, you need 2″×6″ size of rafter placed at 16″ apart from centre.
Can you use two by fours for roof rafters?
A 2×4 can span a maximum of 6' 7” when spaced 16” apart and used as a floor or deck joist. When used as a ceiling joist or a roof rafter, a 2×4 can span up to 7' 3” spaced at 16”, and 6' 4” when spaced 24” apart.
Do I need treated timber for rafters?
All roof timbers including joists, wall plates, blocking, strutting, battens, firrings and noggings must be preservative-treated unless the timber used is naturally durable.
Can you use treated plywood for roofing?
Only use CDX plywood for the interior of a house, where water damage is far less likely. Do not use CDX for roofing, sheds, or other places that are exposed to moisture consistently. The sole exception to this is pressure treated CDX, which can survive for decades without even a protective coating.
Do I need treated timber for rafters?
All roof timbers including joists, wall plates, blocking, strutting, battens, firrings and noggings must be preservative-treated unless the timber used is naturally durable.
Should shed rafters be pressure treated?
It is ideal to choose pressure-treated lumber to construct a shed, especially for areas that will routinely come in contact with the ground, moisture, or pests. A shed that is out in the open and exposed to the elements should be pressure treated, including the structure's framing.
Can you use pressure treated wood for framing?
The simple answer is yes, pressure-treated lumber can be used in any interior application except cutting boards and countertops.
What are two disadvantages of using treated lumber?
Chemical risks. Because this type of decking is treated with chemicals for protection, it can be hazardous when not handled correctly. If the wood is burned, trimmed, or cut, it can release harmful toxins into the air. Pressure-treated wood should not be used for gardens or come in frequent contact with food and water.
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.
FAQ: Pressure-Treated Wood | Simpson Strong-Tie
Waterborne, Creosote, and Oil-borne (penta) are the three broad classes of preservatives typically used when pressure-treating wood. Wood treated with waterborne preservatives is typically used in residential, commercial and industrial building structures.
4-in x 6-in Pressure Treated Lumber at Lowes.com
Find 4-in x 6-in pressure treated lumber at Lowe's today. Shop pressure treated lumber and a variety of building supplies products online at Lowes.com.
How wide should a 2x4 rafter be?
While the heavy load span specs for a 2×4 rafter are much less than a light load, they would allow you to have a shed width of over 14 with a gable roof. It will make less sense to use 2×4 rafters on a single slope shed roof if you live an area with heavy snowfall.
Why do you need a rafter tie?
Rafter ties resist the outward thrust that rafters exert on the exterior walls. They help keep walls from spreading due to the weight of the roof. Rafter ties are always required unless the roof has a structural ridge, or is built using engineered trusses.
What is the first step in conventional roof framing?
The first step in conventional roof framing is to layout and cut a common rafter pattern. The rise and run of the common rafter will determine the height of the ridge board as well as the length of any hip / valley rafters that may be involved with a conventionally framed roof. Conventional framing of roofs falls under the heading of rough framing carpentry. Anyone who has ever tried framing a roof can tell you it is a fine tuned skill that can only be acquired with experience.
How long does a 2x4 shed roof span?
As mentioned above, a 2×4 SPF shed roof rafter can span 11. An SYP rafter can span 11 ½. Both of these are for light roof loads.
What are the diagonal members that directly support the roof deck?
The rafters are the diagonal members that directly support the roof deck.
What is the span distance for a 2x4 roof?
If you have a single sloped roof, then the 11 span distance for 2×4 rafters O.C. means that your shed should be no wider or longer depending on how you orientate your single sloped roof than 11.
How to measure the run factor of a roof?
So, first, divide the width of the exterior structure frame in inches by the number two. This lets you know the run for one side of the roof. Then, divide the run by 12 to find the run factor. The 12 is actually for 12 inches. The outside of the width of the wall framing should be measured on the actual structure frame. Dont add in the siding of the structure or sheathing if there is any.
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.
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.
What are the ratings for PT lumber?
There are three ratings for PT lumber - above ground, ground contact, and direct burial. The PT plywood that's available in my neck of the woods is above ground only. So your comparison may not be valid. http://grantlogan.net
Is it better to build a roof with a PT or a PT?
The normal preference is to build a roof that will not leak through to the sheathing, nor wick water in at the edge. I don't think anyone here will disagree that PT is the way to go if you are anticipating that the roof will fail. If that is your expectation, then PT is the way to go. Good luck with it!
Can you use PT on a roof?
Using PT for residential roof decking is like using greenboard through the interior just 'cuz the walls might someday get wet.
Is there anything wrong with PT decking?
I think didithimselfer got someone from somewhere else to agree with him and is not listening to the builders. There's nothing really wrong with using PT decking, just as there's nothing wrong with using greenboard throughout a house. Preparing for a leak rather than preventing it.
Can you use PT plywood on a deck?
A properly constructed deck should not require use of PT plywood. You may need more of an overhang with functioning drip edges. Covering the whole deck with bituthane is an option, but this still doesn't address any overhang issues. If you decide to use PT sheathing, you'll probably want to use stainless or copper nails, but I really don't think that's an appropriate solution.
Can PT be used on a roof deck?
Which I have been told are built in northern Canada! Imagine that, a wooden foundation wall! So, PT is an excellent usage on low or flat roof decks.
Can plywood be used to fix a low pitch roof?
Treated plywood isn't going to solve your problem if the roof pitch is to low for shingles. It is just going to hide the problem untill your rafters have rotted out.
What is the best plywood for a roof?
The most popular plywood is T&G exterior 3 /8″ pressed board . It's still 4′ x 8′ sheets with a tongue and groove on opposite sides. Therefore you're getting a solid surface. A pressed board is less costly than plywood but much better than fiber board. You can spend more and use 1/2″ to 5/8″ plywood but it's not necessary. If you do, I recommend using aluminum clips between layers. Also, if you begin with a full sheet on the first row next to the roof edge, use a half sheet on the next row so you're not having a continuous seam. Refer to the building codes for your area. It may say using 3/8″ or 1/2″ full sheets with clips on the roof and use T&G on the flooring. Your builder material supplier will tell you what to use for your area. Also, most trusses are spaced 24″ on center. Once the trusses are installed, use 2x4’s to stabilize the trusses below the top deck.
What is the stress rating of a timber frame?
Now, every piece of timber has an ‘’F” rating (stress) and is graded with certain requirements, for a house frame. Stress grades are known by either: ‘ F’ grades F4 to F34: E.g. F14 indicates that the basic working stress (in bending) for that timber is around 14 MPa.
What is the roof joist called?
Essentially, roof rafters and roof joists perform the same function, but on a flat roof they are often called joists instead of rafters.
What is the structural member that runs vertically from a wall, valley rafter or hip to a hip?
On a pitched roof , the structural member that runs vertically from a wall, valley rafter or hip to a hip rafter, ridge, or ledger board is called a roof rafter .
What is the most common wood species?
There are many species - redwood,cedar,spruce,pine,fir but the most common with strength, weight and expense involved and factored in would likely be Douglas fir. All these conifer species can produce material of length for most components. Engineered wood will produce greater sizes of both girth and length.
Do rafters extend beyond the top of a wall?
Since rafters extend beyond the top of an exterior wall, there is just not enough height to ‘rep
Can PT lumber warp?
My experience with PT lumber has been that it often arrives wet and has to be dried and in the process of drying it can warp - sometimes quite a bit. So It could make framing unnecessarily difficult. You’d also need extra care on dust protection and cleanup.
