Screed drying time calculator
The calculator needs JavaScript. The worked example, formula and figures below show exactly how it works, so you can do the sum yourself. A guide, not advice. Check your supplier's or maker's figures before ordering.
Short answer
Worked example
| You enter | Value |
|---|---|
| Type of screed | Sand and cement |
| Screed thickness | 65 mm |
| Rule of thumb: days per mm, up to the threshold | 1 days/mm |
| Rule of thumb: threshold thickness | 40 mm |
| Rule of thumb: days per mm beyond the threshold | 2 days/mm |
| Drying conditions | Warm, well ventilated |
About 90 days before testing for floor finishes
| Result | Value |
|---|---|
| Indicative drying time | 90 days |
| In weeks | 12.9 weeks |
| Before laying floor finishes | Measure moisture before laying; a calendar is not a test. Use a hygrometer or the method the floor-finish maker asks for. |
| Stage | Days | Day reached |
|---|---|---|
| First 40 mm | 40 | 40 |
| Next 25 mm | 50 | 90 |
| Test moisture before laying | – | 90 |
Show the working
- First 40 mm × 1 days per mm = 40 days
- Next 25 mm × 2 days per mm = 50 days
- Total: 90 days (a rule of thumb for 65 mm)
How it works
- Sand and cement rule of thumb: 1 day per mm up to 40 mm, then 2 days per mm beyond (our adjustable defaults)
- Days = thickness up to the threshold × first rate + thickness beyond × second rate
- Anhydrite, fast-drying and other screeds: days = thickness (mm) × the maker's days per mm
A rule of thumb, not a test. Measure moisture before laying (hygrometer or the method the floor-finish maker asks for).
Cold, damp or unventilated rooms dry more slowly.
Our default (adjustable)
These are typical planning figures and our own allowances, not facts about your product. Change any of them in the calculator to match your bag, pack or tin.
| Figure | Our default (adjustable) | Kind | Source |
|---|---|---|---|
| Rule of thumb: days per mm, up to the threshold | 1 days per mm | Our assumption Not yet checked against the source | Our choice: change it to suit your job brief v2 G4: rule of thumb commonly quoted for sand–cement screed, 1 day per mm up to 40 mm. Researcher to source to a screed maker or BS 8204 guidance and state it's a rule of thumb. |
| Rule of thumb: threshold thickness | 40 mm | Our assumption Not yet checked against the source | Our choice: change it to suit your job brief v2 G4: the rule of thumb changes rate after 40 mm. Researcher to source. |
| Rule of thumb: days per mm beyond the threshold | 2 days per mm | Our assumption Not yet checked against the source | Our choice: change it to suit your job brief v2 G4: 2 days per mm beyond 40 mm (rule of thumb). Researcher to source. |
Regulations and standards
- BS 8204-1 (screeds): drying guidance
Explained: BS 8204 (screeds).
Our checks use the guidance for England unless a badge says otherwise. Wales, Scotland and Northern Ireland have their own rules: check the source for where you live.