Description
Atlas SMS 30 is a rapid-set, cement-based floor screed in 25 kg bags that flows level on its own, for indoor floors. It levels hollows, slopes and uneven old screeds in one pour from 3 to 30 mm, you can walk on it after about 3 hours, and tiles can go down after about 18 hours on a 3 to 5 mm layer. It is mixed with water only, poured by hand or pumped, and finishes smooth enough for tiles, vinyl, panels, carpet and parquet. It sits in the Renders World self levelling screed range.
Atlas SMS 30 at a Glance
Why buyers choose this screed:
- Back on the floor the same day. Foot traffic after about 3 hours and full load after about 7 days, at about 20 °C.
- Flat without screeding rails. The mix spreads on its own, so even a large room levels without battens or a screeding bar.
- One product from 3 to 30 mm. Thin skims over small dips, thicker pours over sloping floors, or a raised floor that brings two rooms to the same height.
- Low shrinkage. Linear shrinkage is under 0.06 %, about 0.6 mm per metre, so the layer stays whole and bonded even over weaker bases.
- Dry rooms and bathrooms. Living rooms, halls, offices and corridors, and rooms with raised humidity such as a bathroom.
- Over underfloor heating screeds. Atlas recommends it for evening out existing heated, cement and anhydrite screeds before the final floor goes on.
| Property | Atlas SMS 30 |
|---|---|
| Type | Cement-based levelling screed, rapid-set, for indoor use |
| Class (EN 13813) | CT-C30-F7 |
| Compressive / flexural strength | ≥ 30.0 N/mm² / ≥ 7.0 N/mm² |
| Reaction to fire | A1fl |
| Layer thickness | 3 mm to 30 mm, bonded |
| Maximum grain | 0.5 mm |
| Water per 25 kg | 5.0 to 5.5 litres (0.20 to 0.22 l per kg) |
| Working time | about 40 minutes |
| Foot traffic / full load | after about 3 hours / after about 7 days |
| Full setting and drying | 28 days |
| Linear shrinkage | < 0.06 % |
| Working temperature | +5 °C to +25 °C |
| Consumption | 1.65 kg per m² for each mm of thickness |
| Pack | 25 kg foil bag, 9 months from the production date |
Times are for about 20 °C and 55 to 60 % humidity; colder or damper rooms slow them down.
Bases and Floor Finishes It Suits
Atlas SMS 30 is laid bonded to the base, 3 to 30 mm thick:
- Bases: good-quality concrete, cement screed or anhydrite screed, with or without underfloor heating, and terrazzo; timber and OSB floors at 5 to 30 mm after the right preparation.
- Finished floors on top: ceramic tiles, PVC and vinyl, carpet, panels, parquet or an epoxy floor.
The surface is very smooth and the grain fine, which is why Atlas names it for carpet floors in offices, nurseries, schools and flats, where every ridge in the base would show through.
Need more than 30 mm? The SMS60 screed in the same range is made for layers from 3 to 60 mm.
Preparing the Floor
The base must be stable, sound and air dry. Because the mix flows, the room has to hold it like a bath: seal gaps at door openings, pipes and floor edges so it cannot run away.
- Age of the base: cement screed at least 28 days old, concrete at least 3 months. An anhydrite screed may hold no more than 1 % moisture (CM method) and needs a coat of Atlas EPO-S first.
- Holes and deep hollows: fill first with Atlas ZW 330 fast-setting mortar.
- Prime every base: dust off, then prime well with Atlas NKP used undiluted or with Atlas Uni-Grunt Ultra.
Run polyethylene edge tape round the walls. Keep each pour to 36 m² or less with no side longer than 6 m, add joints at door thresholds and round posts, and carry existing structural joints up through the new layer.
Terrazzo and similar hard floors need more work: degrease them, strip off any polish or sealer, and prime with Atlas Ultragrunt 4 hours before pouring.
Timber and OSB floors
The boards must be clean, dry, rigid and free of oil, wax and old coatings; no board or edge may move or bend, so add screws where needed. Sand varnished or painted timber back, vacuum and wipe with a damp cloth, then brush on Atlas Ultragrunt. After about 24 hours at 20 °C, pour Atlas SMS 30 5 to 30 mm thick in one go.
Mixing by Hand or by Pump
- By hand: pour a bag of Atlas SMS 30 into 5.0 to 5.5 litres of clean water per 25 kg bag and mix with a slow drill and paddle until smooth. Mix again after 5 minutes. The mix stays workable for about 40 minutes.
- Flow test: pour 1 litre of fresh mix onto a flat sheet of foil. It should spread to a circle of about 50 to 55 cm; from a 0.5 litre cup, about 35 to 40 cm. Too much water weakens the screed and can leave dark patches on the surface, which come off when the floor is ground.
- By machine: use a mixing pump with continuous water dosing; Atlas suggests about 60 litres per minute. Load the powder into the hopper, set the water to give the flow circle above, and check it again during the pour.
Pouring and Finishing
- Mark the finished height on the walls and across the floor with a spirit level and height pins.
- Plan the pour so each area can be filled and de-aired within about 40 minutes.
- Pour evenly and without stopping up to the marks, leaving no gaps. When working by hand, draw the mix towards you with a long steel float.
- Straight after filling each area, run a spiked roller over it in two directions at right angles to let the air out. Above 20 mm thick, a dappling bar helps.
- Keep the fresh screed out of draughts, direct sun and dry air. Mist it with water or cover it with foil while it sets.
If the surface comes out milky from too much water, or uneven from poor de-airing, sand it and remove the dust before the next coat or the floor covering. Wash tools in clean water straight away; set residue comes off with Atlas Szop.
When the Floor Can Go Down
Times are for about 20 °C and 55 to 60 % humidity, with the moisture limit Atlas sets for each covering.
| Covering | 3–5 mm | 6–10 mm | 11–20 mm | 21–30 mm |
|---|---|---|---|---|
| Ceramic tiles, epoxy floors (moisture 4.0 %) | 18 hours | 48 hours | 72 hours | 96 hours |
| Parquet, PVC, carpet, panels (moisture 2.0 %) | 1 day | 4 days | 5 days | 6 days |
| Waterproofing with Atlas Woder E (moisture 2.0 %) | 1 day | 4 days | 5 days | 6 days |
| Another coat of Atlas SMS 30 | after about 24 hours, primed again | |||
Prime the screed before tiles or a membrane with Atlas NKP or Uni-Grunt Ultra; for wood, vinyl, carpet, panels and epoxy floors, follow the floor maker's instructions.
How Many Bags to Order
Atlas gives an average of 1.65 kg of powder per square metre for each millimetre of thickness. One 25 kg bag therefore covers about:
| Average thickness | Area per 25 kg bag | Bags for 10 m² |
|---|---|---|
| 3 mm | about 5.0 m² | 2 |
| 5 mm | about 3.0 m² | 4 |
| 10 mm | about 1.5 m² | 7 |
| 20 mm | about 0.75 m² | 14 |
| 30 mm | about 0.5 m² | 20 |
The bag counts are rounded up from 1.65 kg per m² per mm. Measure the depth at several points first, because a sloping floor uses more where it is lowest.
Atlas SMS 30: Questions Before You Order
How soon can I walk on Atlas SMS 30?
Atlas SMS 30 takes foot traffic after about 3 hours at around 20 °C. Full load comes after about 7 days, and the screed is fully set and dry after 28 days.
Can I tile the next day?
On a 3 to 5 mm layer, yes: ceramic tiles can go down after about 18 hours, once the screed is at 4.0 % moisture. A 6 to 10 mm layer needs about 48 hours, and thicker layers up to 96 hours.
Can it go over underfloor heating?
Yes. Atlas recommends Atlas SMS 30 for evening out existing heated cement and anhydrite screeds. It is bonded to the screed, 3 to 30 mm thick, after priming.
Will it work on floorboards or OSB?
Yes, if the boards are rigid and screwed down. Sand them clean, prime with Atlas Ultragrunt, wait about 24 hours and pour 5 to 30 mm in one go.
Can I use it in a bathroom?
Yes, Atlas SMS 30 is made for indoor rooms with raised humidity such as bathrooms. In showers and wet zones, add a waterproofing layer such as Atlas Woder E before tiling.
What if my floor needs more than 30 mm?
Fill deep holes first with Atlas ZW 330, or choose the SMS60 screed for layers up to 60 mm.