The Ultimate Guide to Building a Generator Enclosure
Power outages aren’t just inconvenient; they can also be financially devastating. Whether it’s spoiling food, data loss, or business lapses, the consequences of unreliable electricity go much farther than just having to find flashlights and suffer without heating or cooling.
Portable generators can keep your home or business running on backup power when disaster strikes, but in return, this pricey piece of machinery needs to be protected, as well. If you have a generator, you should house it inside a generator enclosure or shed.
Do you want to learn how to build a generator enclosure? Read on for lots of helpful tips.
Reasons to Build a Portable Generator Box
Why do you need an enclosure to house your portable generator? Whether you call it a box, shed, shelter, or enclosure, your generator needs to be protected and integrated into the environment around it. Here are some of the best reasons for building a container for your portable generator.
- Weather: An enclosure protects your generator from weather conditions such as rain, snow, freezing temperatures, and high winds. Not only can harsh weather ruin a generator, but it can void your warranty, too.
- Noise: Do you really want to listen to that motor humming when you’re trying to sleep? Think about it like this: You wouldn’t want to hear your neighbor idling a motorcycle right next door for hours on end. If your generator’s too loud, it might even violate local noise ordinances. An enclosure muffles the noise and helps keep your neighborhood content.
- Wildlife: An enclosure can be especially important in rural areas, as it keeps wildlife away from your generator. Squirrels and other rodents can cause power outages by gnawing through wires, and nesting birds or wasps can create fire hazards. You don’t want to deal with animal droppings, either.
- Security: Be sure your generator is both secure from theft and also safe to be around: You don’t want curious visitors getting trapped or hurt inside the enclosure.
- Storage: An enclosure frees up space in your outdoor storage shed or garage. (Raise your hand if you park in the driveway because the garage is where your generator lives.)
- Aesthetics: Machinery standing out in the open can be unsightly. You can improve the view by choosing a generator enclosure that’s pleasing to the eye and blends in with the surrounding environment.
- Access: Finally, an enclosure provides quick, easy access to your generator in an emergency. You’ll know exactly where it is and how to get to it.
11 Factors to Consider When Planning to Build a Generator Shed
You have a couple of options when it comes to choosing an enclosure: You can buy one readymade or — if you’re a do-it-yourselfer and want to save money — you can build one yourself. Before choosing a portable generator enclosure plan, think about these elements.
Building a shed is almost always cheaper than buying one. Generators can be expensive (a 22-kilowatt air-cooled generator to power a 2,500-square-foot building can set you back $5,000), so you may need to save money where you can. On the flipside, after investing so much money in a piece of equipment, you might not choose to skimp on protecting it.
Consider using weatherproof materials that won’t rot or rust, so your generator can be protected even when bad weather rolls in. Sheet metal is one possibility, as is powder-coated aluminum, which won’t rust or corrode. If you prefer not to work with metal, a sturdy alternative is concrete blocks sealed by mortar, or treated lumber.
Before you decide on the size of your enclosure, be sure your generator itself is big enough to handle the load that will be required of it during a power outage. You don’t want to buy a too-small generator, build an enclosure, then find out they’re both too small.
A correctly sized enclosure will be slightly bigger than the generator, leaving plenty of room on all sides to allow airflow. The more space you have, the easier the generator will be to access, maneuver, and operate.
Consider where on your property you’ll locate the enclosure. The ground should be level, solid, and out of the reach of water. (Don’t place it in a depression or gully.)
The main hazards of generators are toxic fumes, excessive noise, and the potential to start a fire. For these reasons, your generator enclosure also should be far from windows, doors, or outdoor seating areas, in an area free of weeds, tall grass, or other flammable material.
What surface will you be putting the generator on: dirt, grass, gravel, or concrete? A steel-reinforced concrete pad offers the most secure, level, durable, and watertight base, but other materials are also workable. Here are some options:
- Direct contact: The enclosure is set or built directly on grass or dirt. As with a campfire, it’s important to avoid grassy areas and clear away all potentially flammable material under and around the enclosure.
- Gravel: A layer of gravel is spread before setting or building the enclosure on top.
- Concrete: A slab of concrete (sometimes reinforced with steel rebar) is poured and cured before the generator is set atop it and the enclosure is built.
- Patio blocks: If you’ve got a level, cleared ground space, you can use patio blocks or pavers to provide a sturdy base. They’re not as solid as a concrete slab but can provide more stability than direct contact.
Keep in mind that softer surfaces like dirt or grass can dampen generator noise while harder surfaces like concrete, asphalt, or wood tend to amplify it. One potential solution is to lay a rubber anti-vibration mat on the flooring surface before setting the generator on it.
The local climate is an important factor to consider, especially when choosing the container’s materials and surface to set it on. Temperatures and moisture pose dangers to your expensive equipment, even if you keep it out of direct rain, snow, and wind. The enclosure should address the external conditions of your local climate, especially humidity and temperature extremes.
Here are some examples:
- Hot, arid climate: Your generator may get too hot even when it’s not running, and you may need to install a cooling system.
- Cold climate: You may need an external heating unit to keep components and fluids from freezing during winter when they’re not in use.
- Near the ocean: You’ll want the shed to withstand the corrosion that can come with saltwater spray and attendant humidity.
It’s also important to keep your generator dry, especially the outlets. If water gets in, it can stall out the generator and cause permanent damage. Water also can create the risk of electrocution when it comes in contact with any electrical device.
You can access a generator via many kinds of openings, including:
- a lift-up roof or top cover
- one or more single doors
- double front doors or side doors
- swing-open flaps
- or a combination of the above features.
The larger and more numerous channels there are to allow airflow and access the generator’s controls, the better. Whatever access features your shed offers, it’s best to make sure that they a) close tightly against weather conditions when not in use, and b) slide or swing wide to provide ventilation and access as needed.
Generators require ventilation, both to ensure that they work properly and to avoid safety hazards such as toxic fumes, overheating, and the risk of fire. Special consideration should be given to building the proper ventilation features into any enclosure, including:
- Floorboards in wooden structures spaced at least 1/2 inch apart
- Fresh-air louvers built into walls or doors, or at joints; automatic louvers allow for ventilation while keeping out rain and wind, rodents, birds, and insects
- An exhaust fan
- Enough space to leave the shed door open during operation
Never try to connect your home or business to your generator directly using an extension cord. A generator requires a transfer switch to safely connect to a building’s electrical system.
Whether manual or automatic, a transfer switch controls the flow of electricity between your building, the local utility supply, and your generator, sending the flow of electricity in the right direction at the right times to ensure safe operation.
Whatever kind of structure you choose for your generator, it should feature a spot designated for the transfer switch that will keep it dry and offer easy access. Read more about electricity requirements below in the section titled Important Safety Considerations for Generator Shelters.
Gas generators are quite loud. The quietest top-of-the-line inverter models produce around 60 decibels (dB), meaning you can hold a conversation nearby without having to shout. Most go well beyond that, ranging into the 90dB range that can damage hearing. Some generators don’t even list a decibel level rating, so it’s better to be safe and insulate your enclosure well.
Generator noise can be muffled or “baffled” by storage in a “generator quiet box,” equipped with noise reduction materials. Generally, the more layers your generator box has, the quieter it will be. Baffle boxes can reduce noise by 50% or more. See more soundproofing details in the section below titled Soundproof baffle box.
Although a hefty piece of machinery, a generator can be vulnerable in certain circumstances. Installing hardware that lets you lock the enclosure can keep it safe from threats by:
- Thieves: A generator is a valuable piece of equipment — and not just to you. Generator thieves have been known to leave behind a running lawnmower to mask their getaway, hoping that the generator owner won’t notice the slightly different noise.Housing your generator in a locking enclosure can make would-be thieves think twice about trying to steal it. Thieves like easy targets, and if they see a locked enclosure, they’re likely to move on and look for something that won’t provide as much resistance.
- Children: A locking enclosure also keeps kids safe. A generator shed might look like a tempting place to explore, or take cover during a game of hide-and-seek, but a generator is a dangerous piece of equipment that can cause injury.
- Animals: A locking enclosure can also keep animals out when they try to get in, seeking shelter or a spot to nest in.
Types of Generator Enclosures
All enclosures serve the main purposes of protecting and quieting a generator. Since moisture and extreme temperatures are a generator’s worst enemies, weather-protective enclosures are designed and built to protect generators from the elements — some just do it better than others.
There are several types of DIY generator enclosures you can build from a variety of materials. These range across various price points and offer many sizes and design options, from compact boxes to walk-in sheds. Here are a few of the types of generator enclosures you can build:
- Soundproof baffle box: Also known as a sound-attenuating quiet box, this is designed for noise reduction to keep surrounding areas quiet. They’re most effective when lined with sound-absorbing materials like mass-loaded vinyl, medium-density fiberboard, acoustic caulking, and/or green glue sealant.
- DIY wooden shed: A wooden enclosure can be built inexpensively in flat-topped, asymmetrical lean-to with shingles, peaked/gabled, or other styles. Look for plans with multiple hinged or sliding doors or lids.
- Galvanized steel enclosure: This structure is built from sheets of galvanized steel. It’s especially important that metal structures be equipped with adequate hinged openings to provide proper ventilation.
- Concrete block shelter: A structure built of concrete blocks joined with mortar is especially sturdy, soundproof, and secure. It also requires special attention to access and ventilation.
Choosing an Enclosure Plan to Build
Structural plans for building a generator enclosure should provide step-by-step instructions that clearly note the shed’s intended dimensions and list all the supplies and components necessary for building the floor, walls, roof, and doors.
These are some of our favorite designs, but you can find plenty more on Google.
Soundproof baffle box
- Pros: These are specifically designed to keep surrounding areas quiet. This is especially important if you live or work in neighborhoods with little distance between properties, or in communities with strict noise ordinances.
- Cons: They can be more difficult to build than standard boxes, in part because you need to line them with noise-reducing insulation materials. (It’s important to leave enough room for both the generator itself and the insulation.) Ventilation via hinged doors or lids makes operation louder.
- Links to plans:
DIY wooden shed
- Pros: These can be built quickly, and they’re inexpensive. The cost of materials for a wooden shed to house a smaller generator can be about $200 to start.
- Cons: They can let in moisture, dirt, and debris if not properly insulated. They can also present obstacles to access and ventilation unless multiple doors are built in. Wood can become warped over time with exposure to the elements.
- Links to plans:
Shingled asymmetrical lean-to:
Galvanized steel enclosure
- Pros: Durable and secure, these enclosures offer protection from rain, wind, animals, and theft (if locked). They’re corrosion- and fire-resistant and protect against electromagnetic interference. They’re also stronger than resin, offering the most durable protection.
- Cons: Anyone who’s been inside a metal shed on a hot day can tell you it’s stifling inside. Metal enclosures don’t protect well against extreme temperatures, trapping heat easily and requiring extra ventilation. Humidity and dirt can enter at imprecise joints, require extra sealing or gaskets. These structures also have sharp edges, creating a risk of injury during assembly.
- Links to plans:
Concrete block shelter
- Pros: Concrete blocks provide a sturdy option that diminishes noise, keeps out dust and animals, and deters thieves. These are relatively simple to construct and comparatively cheap; blocks cost less than $2 apiece at home improvement stores.
- Cons: This type of material offers little thermal resistance, so you might need additional insulation against heat and cold if you go this route. You’ll also need to be sure you build in enough ventilation. And though the plans can be pretty straightforward, actually working with concrete can be labor-intensive.
- Links to plans:
Important Safety Considerations for Generator Shelters
Because a generator usually is powered by gasoline or another flammable liquid, the same care should be taken as with any internal combustion engine. The site and surface should be level and solid, with no risk of shifting underneath, and well out of the reach of water.
The generator also should be located in an area free of weeds, tall grass, or any other flammable material. If you don’t have such an area on your property, use a weedeater and an environmentally safe weed/grass-killer to clear an area where you can safely site the enclosure to store your generator.
Don’t place your generator under a deck, in a garage, or in any other confined space where toxic fumes could accumulate, even when the enclosure doors are open. Also, be sure it’s far enough away from any potential obstructions that you can open the door(s).
Don’t build your enclosure with a space to store the fuel you’ll use to power your generator. This should be stored in a separate location to minimize the risk of fire.
Easy access is important in an emergency, but because of the numerous hazards that generators can pose— they produce toxic fumes and can create fire hazards easily — be sure to keep enclosures a considerable distance away from your job site, campsite, or building.
The Centers for Disease Control recommends that generators should only be used outside, and should be kept more than 20 feet from doors and windows. Building codes often call for generators to be placed at least 5 feet from flammable material, and 5 feet from any house opening, as well as trees, overhangs, or overhead structures.
Also, the Occupational Safety and Health Administration (OSHA) warns that, because generators are loud, they can cause hearing loss and fatigue. This is another good reason to consider placing a new enclosure well away from your bedroom or other living space.
Adequate ventilation of an enclosure is important for both proper generator operation and optimal safety. According to OSHA, a generator should have 3 to 4 feet of clear space on all sides and above to ensure adequate ventilation.
The enclosure must be ventilated with cutouts that allow for air intake and to exhaust heat and dissipate fumes. Proper airflow to the cooling fan and temperature-monitoring system can prevent overheating and damage to the generator, also minimizing the likelihood of fire.
Be aware that generators give off toxic carbon monoxide (CO) gas, which is a particularly dangerous gas because you can’t smell or see it. People have died from CO poisoning because their generators aren’t properly ventilated.
This danger is especially acute for walk-in enclosures because you’re likely to spend more time there — all the more reason not to store your generator in the garage or any living area, even if the doors and windows are open.
If a shed fills with CO gas, it also can choke the generator engine and cause it to cut off. Battery-operated CO detectors are available, so you can be sure your enclosure is adequately ventilated.
Another safety consideration is the danger posed by spinning fan blades inside a generator enclosure. Generator machinery often includes exhaust and/or internal cooling fans that can run near the access points and control panels. It’s wise to install a wire-cage fan guard or other type of barrier to prevent anyone from being injured on sharp moving parts.
The electrical design for a generator enclosure should include an electrical panel with enough power to serve the generator, exhaust fan, cooling fan, temperature-monitoring system, and a light. Most importantly, the system must include a transfer switch — essentially, the switch that flips when your business or home’s power goes out and the generator goes on.
The National Electrical Code requires that a transfer switch have a three-position switch to prevent backfeed (more on that below). It will be labeled either “line-off-generator” or “on-off-on.”
It might be tempting to save yourself a few hundred bucks and connect your generator directly to your building, via an extension cord. Don’t do it. Without a transfer switch, you run the risk of frying your appliances or damaging your generator.
A transfer switch also saves you money because it automatically switches off when utility power is restored. That way, you don’t have to keep checking to see if your neighbors’ lights have come back on.
Here’s how it works: A transfer switch isolates selected circuits from the power lines, preventing “backfeed,” which occurs when power flows back from a building’s system into nearby power lines. That’s what can damage your generator and appliances. It can also blow out the building’s electrical panel, fry wires, cause a fire, and even injure or kill any utility personnel who might be working on connected lines.
Transfer switches come in two varieties:
These let you manually turn circuits on and off to manage the load on the generator. They’re typically less expensive because of lower installation costs. One potential pitfall: If no one’s there when the power goes out, the electricity will stay off. This can be a problem, for example, with refrigerated products; if you’re away for any length of time, they’re likely to go bad. According to Consumer Reports, you can purchase an interlock device, which covers the main cutoff switch on your service panel, so you can’t turn it on while the generator is running. When your power comes back on, you manually slide the interlock switch back to its normal position. This prevents backfeed because the power flows in just one direction. You can purchase an interlock kit from $50 to $150.
A universal transfer switch (UTS) automatically turns on, turns off, and adjusts the generator’s power flow as necessary. It also monitors your utility power, and when it’s restored, the UTS automatically reconnects your home or business to its utility source and disconnects from the generator. NOTE: The transfer switch is one part of a generator enclosure project that isn’t do-it-yourself. Some jurisdictions require a licensed electrician to be the one to install your transfer switch, and you should always consult one when designing, installing, maintaining, or repairing any electrical components or systems. This goes for an interlock kit, as well as a universal transfer. In addition to installing it correctly, an electrician can tell you whether it will work with your electrical system and whether it complies with local building codes.
General Supplies for Building a Generator Shed
Generator shed plans can vary widely, but these are the supplies and tools required for a typical DIY wooden enclosure with front wall, back wall, side wall, and shingled roof.
NOTE: All lumber and plywood should be flat and straight, not warped, and free of knots, cracks, or decay.
- 2×4 lumber
- Plywood sheets
- T1-11 plywood siding
- Aluminum sheets
- 1/2-inch hardwood railing bars
- Brad nails
- 1-inch machine screws
- Deck screws
- Galvanized screws
- Roofing shingles
- Wood filler
- Wood glue
- Sealant caulk
- Bungee cords
- Louvered vents
- Measuring tape
- Table saw or circular saw
Final Thoughts on Generator Enclosures
Generators are a godsend when storms or other emergencies cause power outages at your home or business. But like any other piece of internal combustion equipment, a generator must be set up to work safely and stored in a proper environment, protected from the elements, wildlife, and other threats.
Look into the many options for building a generator enclosure and find the one that’s right for your needs.