We are approved layers for Tarmac Self-compacting Screeds

Topflow self-compacting screed is a high-performance cement based screed suitable for laying 75mm thick over a structural sub-base (ie. block & beam or concrete) Free flowing Topflow concrete can be placed fast, with the material consolidating easily and effortlessly into the required pour locations. Topflow provides an excellent, smooth surface quality that can be laid perfectly flat for slabs and floors, eliminating the need for floating.

Screed A is self-compacting anhydrite free-flowing screed. it can be laid in areas of up to 2000m2 in just one day & is suitable for foot traffic within 24-48 hours while partitions can be erected just seven days after placing. Stronger than sand cement screed, Topflow Screed A requires no reinforcement and no manual compaction, can be layed just 40mm thick or 50-60mm over UFH. Topflow Screed A is less prone to shrinkage than sand cement screeds and therefore requires fewer construction joints.

Preparation…

The finished floor is only as good as the sub-floor, spending time carefully preparing the floor is worth the effort. The subfloor must be consistently level without any high/low points. We recommend the customer lays the insulation in 2 layers, cut any service pipes/ducts into the bottom layer & pack any voids with dry sand to prevent movement. Overlay with second layer in opposite direction and ensure the insulation is level & solid with no movement. Securely pin or tape 10mm foam expansion joint around the perimeter. Overlay the insulation with 500guage DPM, any overlaps must be min 200mm and all joints taped, lap & tape up the walls by min 300mm.

We recommend underfloor heating is installed by a qualified tradesman and thoroughly tested before the liquid screed is laid. UFH pipes must be filled with water to prevent them floating. If using a stapled system ensure staples are min 400mm spacing, more on the bends. If using a crate system ensure the crates are securely fixed to the insulation and the edges are taped down to prevent the liquid screed getting underneath.

Doorways are susceptible to cracking, to mitigate this we recommend the customer installs an expansion joint across the doorway, the top should be “notched” to allow the screed to flow through during installation. An expansion joint must be used between heated/un-heated floors & if there is an expansion joint in the sub-floor this must be carried through to the topping.

We recommend the customer provides plastic sheeting to help minimise any mess from spillage around the concrete pump.We require a water supply to the concrete pump.
We require an empty skip to dispose of excess/waste material.
We require access to your site at least 24 hours before laying to check the floor preparation & set up the level guides, once in place they mustn’t be moved.
The customer must ensure that the areas to be laid are clean, dry and weather-proof, if windows and doors aren’t in place then openings should be sealed with polythene.

Curing…

The liquid screed must remain undisturbed for 24hrs.
The room must remain sealed for the first 48 hours to avoid rapid moisture loss & shrinkage cracks.
Avoid direct sunlight for 48 hours.

Trafficking…

Light traffic after the first 24 hours. Heavy site traffic is not recommended for at least 72 hours. If heavy site traffic is essential then cover the affected area with plywood sheets, but remove asap to facilitate drying.

Drying…

Drying times vary dependant on humidity & temperature.
Under normal conditions liquid screed will dry at 1mm per day. If the temperature is higher and humidity lower drying time may be reduced.
After 4 days dehumidifiers may be used to accelerate drying,
After 5 days UFH may be switched on, gradually increase the heat by 5°C per day.
The liquid screed must be fully dry before installing finished floor covering.