How to Screed a Floor
Learn the pros and cons., Clean the concrete base., Cover the floor in plastic sheeting., Line walls and pillars with compressible material., Reinforce the screed., Screed the floor.
Step-by-Step Guide
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Step 1: Learn the pros and cons.
An unbonded screed sits on top of plastic sheets instead of directly on the concrete below.
This protects your floor from moisture in the subfloor, and from settling and other issues in the main structure.
However, unbonded screed is more likely to curl.
Reinforcing can help with this problem, as described below.
Due to the risk of curling, an unbonded screed should be at least 50mm (2") thick at all points.
This means pouring a layer at least 70mm (2.75") thick to allow for variations on the sublayer. -
Step 2: Clean the concrete base.
Remove all dust and grease from the concrete before you begin the project. , Lay down polyethylene or PVC sheets to separate the concrete from the screed layer.
Overlap sheets by at least 20 cm (7.9") and tape them together.
Fold the sheets up 10 cm (3.9") onto all walls and pillars. , This protects these surfaces from damage when the screed shrinks.
You may use edging foam, 20mm (0.8") kingspan insulation, or 1 cm (2.5") polystyrene., Unbonded screed is at greater risk of micro cracks, which reduce its strength.
Reduce this risk with one of the following approaches:
Mix polypropylene fibers into the screed mix before adding water (or order ready-to-use screed with polypropylene already added).
Alternatively, position crack control steel mesh over your subfloor so it will sit in the top half of your screed.
If you do not plan to reinforce unbonded screed, it's a good idea to make the screed at least 100mm (3.9") thick.Screed this thick suffers from moisture issues, so consult a contractor about alternative mixes., Once your workspace is ready, skip down to the section below to see instructions for mixing and applying the screed. -
Step 3: Cover the floor in plastic sheeting.
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Step 4: Line walls and pillars with compressible material.
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Step 5: Reinforce the screed.
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Step 6: Screed the floor.
Detailed Guide
An unbonded screed sits on top of plastic sheets instead of directly on the concrete below.
This protects your floor from moisture in the subfloor, and from settling and other issues in the main structure.
However, unbonded screed is more likely to curl.
Reinforcing can help with this problem, as described below.
Due to the risk of curling, an unbonded screed should be at least 50mm (2") thick at all points.
This means pouring a layer at least 70mm (2.75") thick to allow for variations on the sublayer.
Remove all dust and grease from the concrete before you begin the project. , Lay down polyethylene or PVC sheets to separate the concrete from the screed layer.
Overlap sheets by at least 20 cm (7.9") and tape them together.
Fold the sheets up 10 cm (3.9") onto all walls and pillars. , This protects these surfaces from damage when the screed shrinks.
You may use edging foam, 20mm (0.8") kingspan insulation, or 1 cm (2.5") polystyrene., Unbonded screed is at greater risk of micro cracks, which reduce its strength.
Reduce this risk with one of the following approaches:
Mix polypropylene fibers into the screed mix before adding water (or order ready-to-use screed with polypropylene already added).
Alternatively, position crack control steel mesh over your subfloor so it will sit in the top half of your screed.
If you do not plan to reinforce unbonded screed, it's a good idea to make the screed at least 100mm (3.9") thick.Screed this thick suffers from moisture issues, so consult a contractor about alternative mixes., Once your workspace is ready, skip down to the section below to see instructions for mixing and applying the screed.
About the Author
Kenneth Hill
Specializes in breaking down complex organization topics into simple steps.
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