If you’re not a big fan of the typical ridges and valleys series on your metal building, a stucco decorative finish is one alternative you must try. While stucco for metal isn’t the most popular trend around, it often results in a beautiful exterior and gives you the flexibility to mold and paint it into the patterns you want.
Besides, contrary to what most people believe, stucco can be applied to metal buildings, and it will stick just as well as it does on other surfaces – if not better.
Nevertheless, its application technique and requirements are unique, making it a job for a professional.
Yes! As earlier mentioned, stucco can stick to metal.
However, unlike other materials like concrete and masonry, metal requires a steel mesh or other metal lath to improve its adherence to stucco.
But if you want stucco that can be applied directly to your metal building, you can purchase the modern stucco panels which are now available in the market.
Factors to consider before you stucco metal buildings
Even though stucco can stick to metal, it’s important to know that stucco isn’t suitable for every structure. There are several factors you should consider before deciding to stucco your building. These include:
Since applying stucco on metal will require a lath, you’ll need three coats of stucco to achieve the desired finish. This means a heavier stucco weight will be exerted on your building.
Given that the 3-coat stucco can weigh between 10 – 12 pounds per square foot, this weight may be too much on a small metal building.
You’ll need to reinforce your building to account for the newly added weight. The structural modifications required to strengthen the building’s frame will depend on its size.
- Insulation properties
One of the biggest drawbacks of metal is its poor insulation properties. Adding coats of stucco is likely to improve its insulation, whether you’re working on exterior or interior walls.
If you were thinking of adding some insulation to your building, then this is it.
You can even add Styrofoam beneath the stucco layers to add to the needed R-value for your building. Styrofoam is perfect because it comes in a variety of thicknesses, making it easier to find one that fits your need.
- Type of metal building
Finally, how well your stucco sticks to your metal building and the final output will depend on the type of your building.
Most experts recommend using thinner stucco systems, which are usually 2-coats and a base foam, for small metal structures. This is because such stucco is light enough for the average metal gauge and frame to handle.
However, this isn’t to say that thicker stucco (3-coats) won’t work. With proper reinforcement of the building’s frame or siding, any metal building can easily support such a stucco system.
Additionally, large metal buildings with thicker framing and siding will perform well with the added weight from a 3-coat system.
Methods of applying stucco to metal
Among the things that make stucco so appealing is that it offers multiple final ‘looks’ to choose from.
These attractive appearances, commonly known as Exterior Insulation and Finish System (EIFS), are achieved through one of these three application techniques;
- Stucco flex – This is the cheapest option for stucco on metal buildings. It involves spray painting on the metal sidings and foam boards, resulting in a flat stucco appearance. A common issue with this method, however, is that it does a poor job at hiding flaws and imperfections.
- Stucco panels – The use of stucco panels is growing in popularity due to their ease of application. Essentially, the panels can be installed directly onto your metal structure just like the conventional siding. They offer a wider variety of colors, improves the insulation, and gives your building an attractive rugged stucco finish.
- Traditional stucco – This option is the most popular option for many owners. Its finish resembles the stucco on most residential homes. For a successful application, traditional stucco must be incorporated into the design plans of your metal building. However, quite often you may need a spandrel beam to handle the load of the exterior walls. This will significantly increase your overall costs.
Important: Applying stucco over metal, even on just one side of your building may require a local building permit. Most local authorities require you to obtain a permit for all renovation activities that involve structural modifications. Only small repairs and patches might be excluded from this rule.
You should also check your HOA regulations and deed covenants to avoid violating any laws by stuccoing your building.
How to apply stucco on Metal surface (Step by step)
When doing this as a DIY, it’s important to note that due to the need for a metal lath, you’ll have to prepare three coats of stucco i.e., the scratch layer, brown layer, and finish layer.
- Protective gear (Gloves, facemask, goggles, etc.,)
- Common masonry trowel
- Pointed masonry trowel
- Plaster rake
- Stucco spray (optional)
- Power washer
- Roofing nails
- Roofing felt
- 17-gauge metal netting (metal lath)
- Nail gun
- Adhesive agent
- Ready-mix stucco
Step 1: Clean the surface
For stucco to stick properly with metal, it needs to be applied on a clean surface. So, take your power washer and clean all the dirt and debris on the surface. If part of the metal had rusted, you might need to use a brush, water, and some basic cleaner to get rid of it.
If the metal surface was painted, the power washer may not be able to remove all the paint. Therefore, you might have to sand, scrape or strip the paint before finally rinsing with the power washer.
Step 2: Install roofing felt and lath
While this isn’t always necessary, roofing felt comes in handy due to the absorbent nature of stucco. It helps protect your home from adverse weather effects.
To install, nail down the roofing felt on your metal surface using the roofing nails. Do the same for your 17-gauge metal netting (lath) then use the tin snips to cut them into size.
With the lath, ensure that it’s installed facing in such that it leaves some space between the wire and the metal.
Step 3: Mix and apply the first coat
Using the ready-mix stucco, follow the manufacturer’s directions to mix it for application. If you’re mixing stucco ingredients (premixed cement, water, and sand aggregate), use a 1:¾:½ ratio respectively for this first layer (scratch coat).
When applying it, take your trowel and spread the coat of stucco evenly on the metal surface until it’s around ½ inches thick. Exert some pressure when applying to push the stucco through the lath, but be careful not to overdo it.
Finally, moisturize this layer with water then leave it to cure for around 4 hours before applying the brown coat.
Step 4: Mix and apply the second coat
If you’re using the pre-mixed stucco, follow the manufacturer’s instructions for mixing the second stucco layer. If you’re manually mixing everything, mix 1-part cement with 5-part water and 4-part sand.
For application, use a trowel to spread the stucco over the base coat until it’s at least ⅜ inches thick. Be careful not to break the bond with the scratch coat by troweling too much.
Next, use a plaster rake to create some grooves of up to ⅛ inches deep on the surface of this coat
Step 5: Preserve the moisture of the second coat
Before applying the finish coat, give the second coat at least 48 hours to dry as you moisturize it occasionally to protect it from drying prematurely. If you live in a hot and windy area with low humidity, you’ll need to mist the second layer at least twice a day.
Some experts actually recommend letting this coat dry as you moisturize it for up to 21 days. This slow curing will increase its strength making it less susceptible to cracks.
Step 6: Mix and apply the finish coat
For this final coat, mixing the conventional way should be in a 1:3:4 ratio for cement, sand, and water respectively. With premixed stucco, follow the manufacturer’s directions. Depending on your desired finish, you can also add some color or pigment to this mix.
Since it’s the last layer, you’ll have to be extra careful with this application. First, choose your pattern and stick with it.
You may use a trowel or work by hand for this depending on the results you expect.
Apply the coat using the top-down technique to avoid leaving drips on surfaces you’ve already covered. The layer should be around ¼ inches thick.
Finally, leave it to cure and dry for several days before painting the surface if you intend to.
Can you stucco over metal flashing?
Yes! All you’ll need is roofing felt, some cement, and nails. Identify the area you want to add a flashing then cover it with roofing felt.
Once the felt is safely secured over the old one with nails, add one coat of cement then attach your flashing before it completely dries. Press the flashing firmly into the cement then nail it to place. Finally, stucco around that area.
Can you stucco over aluminum siding?
Yes, you can. Stucco can easily be applied over aluminum siding to improve its aesthetics and insulation properties. This could be through the spray-on stucco flex or using stucco panels.
However, this process could be expensive since you’re using a heavier than paint stucco coat. As a DIY, this process is also quite complex and you can easily damage the underlying aluminum.
If you’re considering it, consult a reputable local contractor to help you out.
Benefits of stucco panels for Metal buildings
There are tons of reasons why stucco panels are the best for your metal buildings. For one, they offer an attractive and affordable solution to owners in areas where code restrictions restrict the use of corrugated metal buildings.
Secondly, stucco panels are very easy to install and can work over all existing metal systems. They also come in a wide array of colors and can as well be painted, guaranteeing that you’ll get your desired finish.
Additionally, the panels are very durable with most of them coming with at least 20 years warranty. You’ll therefore get value for your initial investment.
Stucco panels are also known to have a high thermal R-value. This means that it will improve the insulation performance of your metal building, making the structure more breathable.
How much does it cost to stucco a metal building?
The average cost to stucco a metal building ranges between $7 – $10 per sq. ft. This is relatively higher compared to stucco over other materials due to the added costs of the metal lath and the three stucco coats required.
The total costs may also be higher if you’ll require a supporting structure for the walls or siding.
Metal sidings are very durable and can last up to 50 years or more with good maintenance. Its accurate lifespan will mainly depend on the weather and environmental conditions in your area.
Yes. Just like other metals, you can stucco a shipping container by applying stucco over the entire thing – just like you would a residential home. Other alternatives would be to spray stucco directly on the container, or adding a cement board on it then applying a 2-coat stucco over the board.