Interior Screed Ltd – York ‘s leading floor screeding contractor
Our directly-employed Floor Screeders are some of the best in the UK!
Floor screeders usually use a cementitious material made from a 1:3 or 1:4.5 ratio of screeding cement to washed sharp screeding sand. Floor screeds can be applied to either a solid in-situ concrete ground floor slab or onto a precast concrete floor unit usually topped off with an insulation layer.
So far we have installed 300,000m2 of floor screeding!
There are many types proprietary floor screeds on the market and information about these screeds can be obtained from the floor screeding contractor in York and throughout the UK.
We are Nationwide Floor Screeding Contractors, Established in 2010
Floor screeders may directly bond floor screeds to the sub-base, or laid un-bonded floor screeding onto a suitable damp proof membrane or DPM which is placed over the existing floor slab. Alternatively floor screeds may be applied as a floating finish over a layer of rigid insulation.
45,000 tonnes of screed material installed Nationwide
This type of floor screed application is suitable for use with cast-in water pipes to provide underfloor heating, please enquire with Interior Screed Ltd for details.
We supply & install into either Domestic or Commercial buildings
If reinforcement is required within the floor screed, floor screeders can either supply this in the form of a fine metal mesh, polypropylene fibres or a fine glass mesh installed within the floor screeding. Floor screeders may leave the floor screeding as finished, or floated to produce a smooth screed surface on which to lay the specified flooring or particular finish. Ready-mixed sand and cement floor screeds that are factory-mixed and then delivered to site in York offer additional quality assurance over site mixed floor screeds and offer a more consistent screeding material for floor screeders. Liquid and Sand & Cement Screed Nationwide
Floor screeding contractors such as Interior Screed Ltd based in York provide pumpable free-flowing floor screeds or as they are sometimes referred to liquid screeds which can achieve very level finishes. The majority of liquid screeds are anhydrite compounds that are based on a calcium sulphate binder within the liquid screed.
Interior Screed have completed over 7000 contracts throughout the UK
Liquid screeds are quicker to apply than a traditional sand and cement floor screeding however the amount of preparation required in order to accept a liquid screed must be factored in when considering a liquid screed together with building site access restrictions.
We take pride in each and every screeding installation
Floor screeding can be applied to a minimum thickness of 25mm SBR bonded floor screed, 30mm if unbonded, or 35mm – 40mm if a floating finish is required however specialist screeds and highly skilled floor screeders are required.
Floor screeding such a liquid screed and sand / cement screeds can be used in conjunction with underfloor heating systems where a minimum 30mm cover to the pipes is needed. 2,000m²/day may be laid using these screeds however allowance must be made for preparation and site access.
Working for Self Builders and commercial contractors Nationally
Bonded floor screeds are SBR bonded to the floor slab or substrate beneath. An unbonded floor screed is separated from the concrete slab or substrate below using a polythene layer to sperate the screeding. Fully bonded floor screeds should therefore thin, normally less than 50mm.
Our directly-employed operatives carry full CSCS health & safety
Correctly specifying the depth and type of screed in York starts early in the floor screeding design process. The issues that dictate the design of a floor screed include architecturally specified floor finishes, site access issues, site conditions, construction tolerances and the provision of falls. There may also be structural requirements such as preventing disproportionate collapse and the development of composite action with the concrete slab below. Sometimes, the use of a floor screed may have to be avoided.
We carry a vast selection of screeding products
It may well be achieved by specifying tighter construction tolerances and/or structural finishes that are suitable to receive the flooring materials directly. If a floor screed is needed it can be either a traditional cement sand screed or more recently developed proprietary pumpable self-smoothing or liquid floor or flow / flowing screeds or floor levelling.
We work to British Standard as Standard!
When referencing you are able to use BS8204 part 1 as guidance. BS8204 and BS EN 13318:
Levelling screed – floor screed suitably finished to obtain a defined level and to receive the final flooring. It does not contribute to the structural performance of the floor as a whole.
Wearing screeds – screeds that serves as final looring. This term was formerly known as high strength concrete topping coats or in some cases self levelling. It is also used to refer to structural toppings as well as wearing screeding surfaces.
Bonded – floor screeding laid onto a mechanically prepared substrate with the intention of maximising potential bond.
Un-bonded – floor screeding intentionally separated from the substrate by the use of a membrane.
Floating – floor screeding laid on acoustic or thermal insulation. This is a type of unbonded floor screed.
Cement sand floor screed – floor screeding consisting of a screed material containing sand up to a 4mm maximum aggregate size.
Fine concrete screed – floor screeding consisting of a concrete in which the maximum aggregate size is 10mm.
Pumpable self-smoothing screed – screed that is mixed to a fluid consistency, that can be transported by pump to the area where it is to be laid and which will flow sufficiently (with or without some agitation of the wet material) to give the required accuracy of level and surface regularity.
Curling – an upward deformation of the edges of the screed caused by differential shrinkage
Please note pumpable self-smoothing screeds are often known as self-levelling screeds, flowing screeds, free-flowing screeds, liquid screeds.
Below is an example of types of screeds of installed by Interior Screed Ltd in York and throughout the UK
Our Sand & Cement Screeds
Traditional floor screeds and are suitable for all applications, provided they are specified correctly. The biggest drawback is the drying time; BS 8204 estimates the drying time for a sand cement screed as one day for each millimetre of screed thickness up to 50mm thick with half a millimetre thereafter. Further guidance on drying times can be found in the Code.
Our Liquid Screeds / Flow Screeds
Liquid screeds can be laid as bonded or unbonded by floor screeders of floor screeding contractors. They can be laid in much larger areas than cement and sand screeds, around 2000m2/day. Allowance must be made however for preparation and this can be extremely time consuming. Liquid screed cannot be used with reinforcement because the calcium sulfate is corrosive to steel in damp site conditions.
Liquid screeds are generally not suitable for use in damp conditions or where wetting can occur or may occur. These floor screeds are all proprietary products and therefore vary from one supplier or floor screeding contractor to another, the guidance given here is therefore generic and a skilled floor screeding contractor should be consulted before specifying in York or throughout the UK. Liquid screeds are not intended to be used as a wearing screed the floor screeding company should be consulted.
Our Levelling Screeds in York
Levelling screeds may be chosen for various reasons due to site access restrictions. It might be to provide a smoother, finer tolerance of floor screeding surface and be achieved more economically by the use of self leveller. Levelling floor screeds installed by floor screeders are also used to provide falls or to provide a finishing zone in which different types of flooring can be installed in York .
A common use these days is for a floor levelling screed to be used to accommodate underfloor heating.
Our SBR or Fully Bonded Sand & Cement Screeds in York
Sand and Cement floor screeds are given in BS 8204 Part 1, which recommends the minimum thickness of an SBR bonded sand/cement screed should be 25mm. To accommodate possible deviations in the finished levels of the structural concrete or substrate, the specified thickness should normally be 40mm (with a tolerance of ±15mm from datum) this ensures a minimum floor screeding thickness of 25mm thoughout.
Where the bonded floor screeds needs to be greater than 40mm the following options are available to reduce the risk of debonding:
Use modified floor screeding or additives to reduce the shrinkage potential.
Use fine concrete screed, which reduces the shrinkage potential, this has been used successfully up to 75mm.
Use highly skilled floor screeders or floor screeding contractors
Our Bonded Calcium Pumpable Self-smoothing Floor Screeds
Pumpable self-smoothing floor screeds are given in BS 8204 Part 7, which recommends minimum thicknesses of bonded floor screeding should be 25mm. Floor screeding contractors quote maximum thicknesses of up to 80mm and therefore there are less restrictions on the overall screeding thickness. A nominal depth of 40mm with a tolerance of ±15mm can be comfortably specified by floor screeding contractors or floor screeders in York .
Our Un-bonded Cement Sand Floor Screeding
Screed thickness should not be less than 50mm; therefore, to allow for deviations in the finished levels, the specified design thickness should be a minimum of 70mm throughout. BS 8204-1 emphasizes that there is a high risk of the floor screed or screeding curling with unbonded and floating levelling screeds. In order to minimise this, the screeds should be either reinforced across the joints or made 100mm or more in thickness.
Our Unbonded Flowing / Liquid Screeding in York
Screed thicknesses should not be less than 30mm; therefore, to allow for deviations in the finished levels the specified design screed thickness should be a minimum of 45mm for a tolerance of ±15mm.
Thickness of wearing screed (structural topping)
Interior Screed Ltd – Bonded Floor Screeds in York
Wearing screeds are given in BS 8204 Part 2, which recommends the minimum thickness of a bonded wearing screed should be 20mm (in contrast to the 25mm given for a floor levelling screed in Part 1).
To accommodate possible deviations in the finished levels of the structural concrete, the recommended thickness is 40mm. The specification for the base concrete surface should be compatible. In some cases the screed design thickness will have to be increased above 40mm, but it should be noted that there is an increasing risk of de-bonding of the floor screed.
For hollowcore units, which often have an upwards camber, especially for longer spans, a nominal screed thickness of 75mm, rather than 40mm should be specified.
The risk of debonding is mitigated because it is usual to use a concrete of class C25/30 or above and mesh reinforcement and highly skilled floor screeders and floor screeding contractors. Using concrete should ensure there is sufficient depth at mid span (i.e. the point of maximum camber) to allow for lapping the reinforcement whilst still maintaining cover to both surfaces. Loose bars or mesh reinforcement with flying ends may be required to allow lapping of the reinforcement near the point of maximum camber.
Interior Screed Ltd – Unbonded Floor Screeding in York
Wearing screeds should be at least 100mm thick but to minimise the risk of curling, consideration should be given to increasing the depth to 150mm, these types of screeds are often called Granolithic Screeds.
Screeding sector guidance is focussed on selecting the correct thickness for the floor screed. Other criteria may have an impact on the design including:
Slip, abrasion and impact resistance
Type of traffic on the floor
Levels and flatness
Appearance and maintenance
Type of flooring to be used or applied
Drying out moisture in screed
Location of movement joints
Full Floor or Sub-Base Preparation
For all types of bonded floor screeds (both sand/cement floor screeds and calcium sulphate screeding) preparation of the base is of paramount importance in York . Structural concrete base should be at least C28/35 concrete with a minimum cement of 300kg/m3.
Precast units the surface of the units should be left rough during production and should be thoroughly washed and cleaned e.g. by wire brushing to remove all adhering dirt. Joints between the units should be grouted at least one day before the screed is installed by floor screeders. Levelling floor screeding or liquid screeding is designed to act compositely with the units and additional preparation of the units may be required, contained shot blasting equipment can be used to avoid damaging the units.
Floor screeds are required over in-situ concrete then all contamination and laytance on the base concrete should be entirely removed suing suitable mechanised equipment exposing cleanly the coarse aggregate beneath. Loose debris and dirt should be removed preferably by vacuuming in York .