Preparing Surfaces For Microcement

The following guidelines are for the attention of main contractors, builders, architects and clients who are responsible for preparing/specifying surfaces for microcement & subsequent maintenance.  Please read them carefully as early in the build as possible. To see more background see our Microcement guide.

Could you paint it?

The best way to prepare a surface for microcement is to imagine that you are going to paint it. Whilst microcement is very strong & flexible, it is only ever as strong & stable as the substrate that it is going onto. And just like paint, lumps, bumps, gaps and movement are likely to be transferred through to the finished product, which can impair the end result. If you want a smooth finish, future proofed against cracks, you need to be sure that the substrate is smooth & future proofed.

We can assist in getting surfaces up to this standard, but it will be easier & cheaper if this is completed during initial install of sunstrates.

Well Consolidated

Surfaces should be well consolidated, so that no further settlement or movement is anticipated. Cracks in the microcement due to unconsolidated surfaces are the responsibility of the contractor who laid the sub floor not the applicator of the microcement.

We can fill cracks and gaps that have appeared in the surface during the curing process. But, further movement in the sub floor will cause cracks to appear in the surface.

Whilst microcement is very hard, it should be considered as a topping compound only. It is the responsibility contractor who is laying the substrate to ensure that the materials used are fit for purpose & well consolidated.

Cold Joints & Expansion Joints

Wherever 2 separate subfloors meet, whether they have been laid at different times or have intentional expansion joints in them, movement is most likely to occur along the join. If there is movement in the subfloors, this may cause the microcement to crack along the join.

In order to prevent cracks in the microcement caused by cold joints, concrete & screed subfloors should be poured in one complete pour wherever possible, allowing for expansion/control joints as appropriate.

We will insert a bead or threshold to separate the 2 surfaces and microcement up to the bead on either side.

Level Surfaces

Surfaces must the level. Floors that are not level will need to be levelled off with a self-leveller and appropriate acrylic primer. Please leave 4mm to finished floor height for microcement.

Microcement can be laid onto a wide range of surfaces, including concrete, screeds, cement board, ceramic, plasterboard, ply board, chip board & mdf.

It is important to remember that surfaces must be flat & level – so that you would be happy to paint onto them. For that reason, we ask that all walls are plastered.

Microcement cannot be applied directly onto natural timber which is at risk of warping.

Timber floorboards will need to be covered with a suitable cement board.

These should be level & butted up against one another.

Boards need to be firmly fixed in place (glued & screwed as appropriate), so that there is no risk of movement. Boarded areas must be laid flush & level across the entire area. Gaps should be filled with a suitable hard filler, not silicone. Please allow sufficient time for filler to cure before we attend site.

Less than 5% Moisture Content

All surfaces will need to have less than 5% moisture content when we come to install. We can test the moisture content on arrival, but please work to the manufacturer’s recommended lead times for freshly laid surfaces. If surfaces are not dry when we arrive on site, extra costs and/or delays to the build will be incurred.

Hardness Test

We will test concrete floors before we lay microcement & will not proceed if they are less than 4 on the MOHs hardness scale. Floors should be free from dust and excessive laitance.

Access & Floor Prep

The area will need to be completely cleared in advance of us starting work.  There will be no access to other trades for the time it takes us to complete the work (usually 7 days). We would prefer that skirting boards & kick boards are removed/left off prior to work commencing.

Water Tight

There must be no risk of water getting to the microcement from outside - e.g. through open windows / doors or rising damp.
There must be no risk of water or other liquids touching the microcement whilst we are working in the room, as this will cause stains & further work that we will have to charge for.

Until sealed, the microcement will be very porous so any water spilt on the surface will stain. Anyone who spills water on the surface or marks it in any way must take responsibility for the cost of repairs.

Curing Times

The microcement will not be fully cured until 4 weeks after it has been laid. Please take care not to scratch, cut, drop or drag items on the floor during this time. The cost of repairing any damage caused will need to be paid by those responsible.

Once cured, microcement is strong, anti-slip and has a good resistance to stains. You can treat it as you would a hard wood floor.

Underfloor Heating

Underfloor heating must have been commissioned and been put through a full cycle (from lowest to highest temperature at intervals as recommended by screed and underfloor heating manufacturers) before we arrive on site.

Unless directed otherwise, please ensure underfloor heating is turned off 48 hours before work is due to start & keep it off for the duration of the work.

After applying the microcement, at least 48 hours should pass before the heating is gradually turned on (+5°C each day).

Maintain the water entering the circuits at 25°C throughout 2 or 3 days. Then gradually increase the water temperature to 45°C and keep it on for several days.

Always change the temperature gradually, both at the beginning and at the end of the heating period.

Ensure the heating is turned on within 4 weeks of us laying the floor.

Make sure that the relative air humidity in the rooms is not too low.

Always avoid an accumulation of heat caused by rugs and carpets, or the lack of space between the furniture and the floor.

Additional Requirements for Showers & Wet Rooms

Prior to microcementing, shower area walls must be plaster boarded right down to the shower trays & then plastered. Please take care to ensure boards are fixed to the walls & silicone the joint between the boards & the shower tray/floors.

Hard shower trays that are suitable for vinyl floors (e.g. Marmox Showerstone) should be firmly fixed into place to avoid movement. It is the responsibility of the sub-contractor who fits the tray to ensure that the falls are sufficient for water to flow towards the drain.

There should be no gaps between shower trays & adjacent flooring. Please leave 4mm to finished floor height for microcement.

Caring for Microcement Surfaces

First 7 Days

Like all concrete, microcement takes 28 days to full harden. It’s at it’s softest for the first 7 days after laying. During this time it should only be subjected to light use and light foot traffic.

Any heavy work is not recommended, but if it does take place then we recommend that you cover the floor with a breathable material or only cover down whilst working & lift the protection off for the majority of the time. The surface needs to dry out and harden. If air flow is restricted, it will stain & not cure correctly.

Fixing to Surfaces after Microcement is Installed

Microcement can be drilled and screw into using drill bits that are suitable for the substrate.
Because it is the sealers that make microcement waterproof, any holes or cuts will need protecting from moisture penetration by either putting silicone into screw holes or by surrounding fixtures & fitting entirely with silicone. Care must also be taken not to scratch the sealers whilst installing fixtures & fittings.

No Dragging of Dropping

Dragging heavy objects over the surface is not recommended, as damage could occur. To move furniture: it is advisable to lift and support, never to drag. It is necessary to protect flooring, with lids or felts, from the pressure points of furniture (metal feet, sharp surfaces), or objects with abrasive or heavy contact surfaces.

Despite its lack of thickness, one of this material’s most significant properties is its high resistance and hardness; some of the products can even be used in areas of high traffic.

Several factors influence the resistance and hardness of microcement, such as the support on which it is applied, the type of microcement chosen, as well as the sealer used.

We can differentiate between two types of resistance:

Mechanical Resistance

To blows: Microcement, due to its limited thickness, will deform in the event of a strong blow if the support beneath deforms. An example would be the microcement applied to plaster. If the base deforms because it has poor resistance, the microcement will deform as well. While on a support like terrazzo, the resistance will be greater.

To abrasion and wear: This resistance depends on both the microcement type and the sealer. Generally, abrasion resistance is comparable with hard wood.

Resistance to Stains

Chemical resistance depends on the sealer used to protect the product. Are sealers are among the best in the industry for both hardness & strength.

Both vinegar or lemon juice leave slight marks on microcement. These acids affect the surface as they would on marble, but if cleaning is done quickly, they won’t stain.

Hydrochloric acid, pure bleach, acetone and ammonia will mark after a half hour of exposure, but if cleaning is done quickly, no stains will remain.

If water stains appear within the 1st 4 weeks of use, keep the area dry & alert us immediately as stains will become permanent if not treated quickly.

Prolonged Exposure to Water

If water is trapped against the surface for a prolonged length of time it may stain & potentially cause the microcement to blister. Please refrain from leaving wet towels, plant pots, wet shampoo bottles etc in contact with the microcement.

Cleaning

To ensure the long and durable life of our microcements, we recommend the use of water and neutral soaps.

The care of microcement is similar to that of natural wood parquet. We advise to avoid permanent wetness, or prolonged contact with moisture. Leaving wet carpets and towels on the floor is ill-advised, as are pots that leak. The surfaces should also be kept free of stones or grit which can scratch the coating. Avoid any blows and rubbing with hard objects.

Although microcement offers a high resistance to chemicals, cleaning should be done with neutral soaps, never with aggressive or descaling products. Additionally, avoid products such as chlorine, bleach, ammonia, soaps and detergents in general, as they can damage the protective film.

Any Questions?

Please feel free to get in touch. 07487 247 388 | info@relentlessinteriors.com

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