How to Stucco a House
Check the weather forecast., Put up sheathing materials., Cover the plywood with two layers of building paper., Install weep screeds and casing bead., Attach metal lath., Install control joints., Mix the scratch coat., Trowel the scratch coat into...
Step-by-Step Guide
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Step 1: Check the weather forecast.
The ideal weather conditions for applying stucco involve an overcast day with low wind, and temperatures of 50 to 60ºF (10–16ºC).Delay the job if the temperature is expected to drop below 40ºF (4ºC) or rise above 90ºF (32ºC) in the next week., You may stucco over any rigid material attached to your support studs.
The most common surfaces for stucco are plywood, oriented strand board (OSB), cement board, and exterior grade gypsum sheathing.Make sure to follow local building codes while installing the sheathing material.
It is possible to stucco over an open frame, but this results in a less even and less structurally secure wall.
If you plan to go this route, drive nails halfway into the studs, spaced out vertically in 5-6 inch (13-15 cm) intervals.
String line wire horizontally along the protruding nails., Most building codes require at least two layers of "Grade D" building paper or an equivalent water-resistant barrier.You may use asphalt felt or some types of housewrap, but do not use a plastic housewrap not intended for stucco.Overlap the paper by at least 4 inches (10 cm) and fasten with roofing nails.While not required by most codes, an air gap between the two layers is highly recommended to prevent wall rot.
A 3D plastic drainage mat between the two barriers is one way to accomplish this., Install casing bead as a plaster stop at the corners of doors and windows.Install weep screed at the base of the wall for better drainage.For this project, these two materials are not interchangeable., Selecting the correct lath and installing it properly is one of the more difficult parts of this project.
Consulting a local contractor is recommended.
In most cases, you should nail or staple the lath to the studs (not the sheathing) at no less than 7 inch (18 cm) intervals.
Overlap the lath by at least ½" (1.25 cm) along the long side and 1 inch (2.5 cm) at the end, but not much more.In all exterior stucco applications, you must use G-60 hot-dipped galvanized lath.Choose lath with at least ¼" (6mm) furring, or make up for non-furred lath using furring strips or furring nails.Without this furring, the stucco will not adhere properly to the lath. , To reduce cracking, divide the wall into rectangular panels using control joints, spacing them no more than 18 ft (5.5 m) apart.
Also install control joints wherever two dissimilar walls meet.If the lath is expanded metal (rather than stucco mesh), cut it behind each control joint to fully separate this rigid material into panels.Make the panels as close to square as possible, and no larger than 144 ft2 (13 m2)., Mix the scratch coat from 1 part cement material and 2¼ to 4 parts plaster sand.
If you are using Type I Portland cement instead of plastic cement, you'll need to add your own hydrated lime; count the final cement and lime mixture as the "1 part cement."Mix with just enough potable water that you can trowel the stucco; any more, and it is likely to sage.
The aggregate in the cement should be clean and well graded. , Apply the scratch coat with a square trowel at a 45º angle, firmly pushing it into the lath.
This layer should be ⅜" (9.5 mm) thick.You may find it easier to use a hawk for some portions of the application. , The first coat is called the "scratch coat" because of the shallow, horizontal lines scored into it by a notched trowel.
This will ensure a good bond with the next coat. , When stuccoing over stud construction, the thick scratch coat must be allowed to cure for 48 hours.
During this time, it is critical to protect the stucco from drying out.
Mist or fog the stucco twice daily unless the relative humidity is above 70%.
Protect the wall with a windscreen or sunshade if necessary. , Mix another batch using 1 part cement and 3 to 5 parts sand.
Apply another ⅜" (9.5 mm) layer of stucco and screed to an even thickness, for a total thickness so far of ¾" (19 mm).Once the brown coat loses its sheen, float it smooth. , Wet cure as you did the scratch coat, but this time allow at least seven days.
The first 48 hours are the most important, but you should continue to mist or fog it for this whole period, whenever it looks like it's about to dry. , This final ⅛" (3 mm) layer determines the texture of your stucco wall.Apply and float it as you did the brown coat, but this time use 1 part cement to 1½ to 3 parts sand.
You may purchase a finish which already contains pigment, or trowel on a plain finish and paint over it once it has had at least a week to cure.
Colored stucco finishes work best in pastel shades.If the finish is colored, wetting the surface during floating may cause mottling.
A fog coat may make the color more even.
Many decorative textures are possible when applying this final layer.
Judge the appearance from at least 30 feet (9m) back before settling on a look. -
Step 2: Put up sheathing materials.
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Step 3: Cover the plywood with two layers of building paper.
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Step 4: Install weep screeds and casing bead.
-
Step 5: Attach metal lath.
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Step 6: Install control joints.
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Step 7: Mix the scratch coat.
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Step 8: Trowel the scratch coat into the lath.
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Step 9: Score the scratch coat lightly.
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Step 10: Wet cure the scratch coat.
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Step 11: Mix and apply the brown coat.
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Step 12: Wet cure for at least seven days.
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Step 13: Cover with the finish coat.
Detailed Guide
The ideal weather conditions for applying stucco involve an overcast day with low wind, and temperatures of 50 to 60ºF (10–16ºC).Delay the job if the temperature is expected to drop below 40ºF (4ºC) or rise above 90ºF (32ºC) in the next week., You may stucco over any rigid material attached to your support studs.
The most common surfaces for stucco are plywood, oriented strand board (OSB), cement board, and exterior grade gypsum sheathing.Make sure to follow local building codes while installing the sheathing material.
It is possible to stucco over an open frame, but this results in a less even and less structurally secure wall.
If you plan to go this route, drive nails halfway into the studs, spaced out vertically in 5-6 inch (13-15 cm) intervals.
String line wire horizontally along the protruding nails., Most building codes require at least two layers of "Grade D" building paper or an equivalent water-resistant barrier.You may use asphalt felt or some types of housewrap, but do not use a plastic housewrap not intended for stucco.Overlap the paper by at least 4 inches (10 cm) and fasten with roofing nails.While not required by most codes, an air gap between the two layers is highly recommended to prevent wall rot.
A 3D plastic drainage mat between the two barriers is one way to accomplish this., Install casing bead as a plaster stop at the corners of doors and windows.Install weep screed at the base of the wall for better drainage.For this project, these two materials are not interchangeable., Selecting the correct lath and installing it properly is one of the more difficult parts of this project.
Consulting a local contractor is recommended.
In most cases, you should nail or staple the lath to the studs (not the sheathing) at no less than 7 inch (18 cm) intervals.
Overlap the lath by at least ½" (1.25 cm) along the long side and 1 inch (2.5 cm) at the end, but not much more.In all exterior stucco applications, you must use G-60 hot-dipped galvanized lath.Choose lath with at least ¼" (6mm) furring, or make up for non-furred lath using furring strips or furring nails.Without this furring, the stucco will not adhere properly to the lath. , To reduce cracking, divide the wall into rectangular panels using control joints, spacing them no more than 18 ft (5.5 m) apart.
Also install control joints wherever two dissimilar walls meet.If the lath is expanded metal (rather than stucco mesh), cut it behind each control joint to fully separate this rigid material into panels.Make the panels as close to square as possible, and no larger than 144 ft2 (13 m2)., Mix the scratch coat from 1 part cement material and 2¼ to 4 parts plaster sand.
If you are using Type I Portland cement instead of plastic cement, you'll need to add your own hydrated lime; count the final cement and lime mixture as the "1 part cement."Mix with just enough potable water that you can trowel the stucco; any more, and it is likely to sage.
The aggregate in the cement should be clean and well graded. , Apply the scratch coat with a square trowel at a 45º angle, firmly pushing it into the lath.
This layer should be ⅜" (9.5 mm) thick.You may find it easier to use a hawk for some portions of the application. , The first coat is called the "scratch coat" because of the shallow, horizontal lines scored into it by a notched trowel.
This will ensure a good bond with the next coat. , When stuccoing over stud construction, the thick scratch coat must be allowed to cure for 48 hours.
During this time, it is critical to protect the stucco from drying out.
Mist or fog the stucco twice daily unless the relative humidity is above 70%.
Protect the wall with a windscreen or sunshade if necessary. , Mix another batch using 1 part cement and 3 to 5 parts sand.
Apply another ⅜" (9.5 mm) layer of stucco and screed to an even thickness, for a total thickness so far of ¾" (19 mm).Once the brown coat loses its sheen, float it smooth. , Wet cure as you did the scratch coat, but this time allow at least seven days.
The first 48 hours are the most important, but you should continue to mist or fog it for this whole period, whenever it looks like it's about to dry. , This final ⅛" (3 mm) layer determines the texture of your stucco wall.Apply and float it as you did the brown coat, but this time use 1 part cement to 1½ to 3 parts sand.
You may purchase a finish which already contains pigment, or trowel on a plain finish and paint over it once it has had at least a week to cure.
Colored stucco finishes work best in pastel shades.If the finish is colored, wetting the surface during floating may cause mottling.
A fog coat may make the color more even.
Many decorative textures are possible when applying this final layer.
Judge the appearance from at least 30 feet (9m) back before settling on a look.
About the Author
Peter Thomas
Brings years of experience writing about creative arts and related subjects.
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