Screed - Revision history

Designing Buildings at 09:41, 15 September 2020

2020-09-15T09:41:41Z

← Older revision		Revision as of 09:41, 15 September 2020
Line 74:		Line 74:
	* [http://www.cscscreeding.co.uk/screed-systems/fast-drying-floor-screed/ CSC Screeding]		* [http://www.cscscreeding.co.uk/screed-systems/fast-drying-floor-screed/ CSC Screeding]

−	[[Category:Construction_techniques]] [[Category:Design]]	+	[[Category:DCN_Definition]] [[Category:DCN_Guidance]] [[Category:DCN_Product_Knowledge]] [[Category:Construction_techniques]] [[Category:Design]]

Designing Buildings at 15:06, 26 April 2019

2019-04-26T15:06:40Z

← Older revision		Revision as of 15:06, 26 April 2019
Line 56:		Line 56:
	* Cement.		* Cement.
	* Concrete.		* Concrete.
−	* Damp proof membrane (DPM).
	* Floor definition.		* Floor definition.
	* Floor screed costs.		* Floor screed costs.
	* Flooring.		* Flooring.
	* Insulation.		* Insulation.
		+	* Laser screed.
	* Portland cement.		* Portland cement.
	* Power float.		* Power float.
Line 66:		Line 66:
	* Reinforced concrete.		* Reinforced concrete.
	* Rendering.		* Rendering.
−	* Separating floor.
−	* Substructure.
−	* Tiled floors with underfloor heating: A guide to minimising and repairing cracking.
−	* Underfloor heating.
	* Wet trades.		* Wet trades.

Designing Buildings at 13:42, 14 February 2019

2019-02-14T13:42:49Z

← Older revision		Revision as of 13:42, 14 February 2019
Line 54:		Line 54:

	* Aggregate.		* Aggregate.
−	* Basement.
	* Cement.		* Cement.
−	* Concept structural design.
	* Concrete.		* Concrete.
	* Damp proof membrane (DPM).		* Damp proof membrane (DPM).
	* Floor definition.		* Floor definition.
		+	* Floor screed costs.
	* Flooring.		* Flooring.
−	* Grout.
−	* Harl.
	* Insulation.		* Insulation.
−	* Lath and plaster.
−	* Mastic sealant.
	* Portland cement.		* Portland cement.
	* Power float.		* Power float.
Line 71:		Line 66:
	* Reinforced concrete.		* Reinforced concrete.
	* Rendering.		* Rendering.
−	* Sealant.
	* Separating floor.		* Separating floor.
−	* Stucco.
	* Substructure.		* Substructure.
	* Tiled floors with underfloor heating: A guide to minimising and repairing cracking.		* Tiled floors with underfloor heating: A guide to minimising and repairing cracking.
Line 79:		Line 72:
	* Wet trades.		* Wet trades.

−	=== External references ===	+	= External references =

	* [http://www.concrete.org.uk/ Concrete]		* [http://www.concrete.org.uk/ Concrete]

Editor at 16:38, 12 November 2018

2018-11-12T16:38:42Z

← Older revision		Revision as of 16:38, 12 November 2018
Line 17:		Line 17:
	=== Bonded screed ===		=== Bonded screed ===

−	The screed layer is fully bonded to the substrate using a primer or bonding agent. This method is commonly used for thinner screeds where heavy loading is expected and where there is not enough space available to lay an unbonded screed. The optimum thickness of a sand and cement bonded screed is generally in the region of 25-~~40mm~~. Some calcium sulphate flowing screeds can be laid at a minimum depth of ~~12mm~~. Care must be taken during the laying process to ensure de-bonding does not occur as this can lead to instability and ultimately, the screed may fail.	+	The screed layer is fully bonded to the substrate using a primer or bonding agent. This method is commonly used for thinner screeds where heavy loading is expected and where there is not enough space available to lay an unbonded screed. The optimum thickness of a sand and cement bonded screed is generally in the region of 25-40 mm. Some calcium sulphate flowing screeds can be laid at a minimum depth of 12 mm. Care must be taken during the laying process to ensure de-bonding does not occur as this can lead to instability and ultimately, the screed may fail.

	=== Unbonded screed ===		=== Unbonded screed ===

−	Instead of being bonded directly to the base, unbonded screeds are applied over a damp proof membrane (DPM) laid on top of the concrete base. The minimum thickness of an unbonded sand and cement screed is usually in the region of ~~50mm~~. Calcium Sulphate screeds can be laid unbonded at a minimum depth of 30 mm. The advantage of an unbonded screed is that the flooring is not in direct contact with the main structure and so the potential impacts of settlement or shrinkage can be less problematic. The DPM creates a barrier preventing damp rising from the substrate.	+	Instead of being bonded directly to the base, unbonded screeds are applied over a damp proof membrane (DPM) laid on top of the concrete base. The minimum thickness of an unbonded sand and cement screed is usually in the region of 50 mm. Calcium Sulphate screeds can be laid unbonded at a minimum depth of 30 mm. The advantage of an unbonded screed is that the flooring is not in direct contact with the main structure and so the potential impacts of settlement or shrinkage can be less problematic. The DPM creates a barrier preventing damp rising from the substrate.

	However, this type of screed can be more prone to curling if dried quickly. Curling is a vertical distortion of the edges due to temperature differences or moisture content throughout the thickness of the screed. This can be prevented by adhering to minimum specified thicknesses and allowing for slow drying. Calcium Sulphate screeds are not prone to curling due to their lower rates of shrinkage compared to sand and cement screeds.		However, this type of screed can be more prone to curling if dried quickly. Curling is a vertical distortion of the edges due to temperature differences or moisture content throughout the thickness of the screed. This can be prevented by adhering to minimum specified thicknesses and allowing for slow drying. Calcium Sulphate screeds are not prone to curling due to their lower rates of shrinkage compared to sand and cement screeds.
Line 29:		Line 29:
	The screed is laid on top of insulation to create a thermally efficient floor. Floating screeds are commonly used where underfloor heating systems are provided or thermal or acoustic insulation is required. Floating sand and cement screeds generally have a thickness greater than 65 mm for lightly-loaded floors and 75 mm for more heavily-loaded floors. Calcium Sulphate floating screeds can be installed at 35 mm depth for domestic use or 40 mm for commercial use.		The screed is laid on top of insulation to create a thermally efficient floor. Floating screeds are commonly used where underfloor heating systems are provided or thermal or acoustic insulation is required. Floating sand and cement screeds generally have a thickness greater than 65 mm for lightly-loaded floors and 75 mm for more heavily-loaded floors. Calcium Sulphate floating screeds can be installed at 35 mm depth for domestic use or 40 mm for commercial use.

−	=== Flow / ~~Liquid~~ Screed ===	+	=== Flow/liquid Screed ===

	Liquid flow screed is fast becoming the industry standard in floor screeds. This type of floor is also referred to as self compacting screed or a calcium sulphate screed. Simple in its preparation this new form of flow screed is suitable for light foot traffic in 24-48 hours. Partitions can be installed and/or the screed can be loaded out 7 days after installation.		Liquid flow screed is fast becoming the industry standard in floor screeds. This type of floor is also referred to as self compacting screed or a calcium sulphate screed. Simple in its preparation this new form of flow screed is suitable for light foot traffic in 24-48 hours. Partitions can be installed and/or the screed can be loaded out 7 days after installation.
Line 37:		Line 37:
	This is where the floating screed layer is installed over underfloor heating pipes or insulation. The screed serves to conduct the heat evenly across the floor surface, avoiding hot or cold spots, and helps to retain heat for longer. In order that heat propagates only in the required direction of the room to be heated or cooled, the elements are inserted above insulating panels. Sand cement screeds require a minimum thickness of 65 mm, with the ideal being between 65-75 mm.		This is where the floating screed layer is installed over underfloor heating pipes or insulation. The screed serves to conduct the heat evenly across the floor surface, avoiding hot or cold spots, and helps to retain heat for longer. In order that heat propagates only in the required direction of the room to be heated or cooled, the elements are inserted above insulating panels. Sand cement screeds require a minimum thickness of 65 mm, with the ideal being between 65-75 mm.

−	Where fibres are added or when using anhydrite screeds the minimum thickness may be reduced to 50 mm. Some specialised calcium sulphate screeds can be installed with only 20 mm cover to the heating pipes, giving screed depths of less than 40 mm Care must be exercised in allowing adequate drying time (usually around 21 days) before incrementally turning on the heating system, otherwise cracking may occur. Additives can be included in the screed mix to allow the drying time to be reduced. Calcium sulphate screeds can be force dried, using the underfloor heating, after 7 days.	+	Where fibres are added or when using anhydrite screeds the minimum thickness may be reduced to 50 mm. Some specialised calcium sulphate screeds can be installed with only 20 mm cover to the heating pipes, giving screed depths of less than 40 mm.
		+
		+	Care must be exercised in allowing adequate drying time (usually around 21 days) before incrementally turning on the heating system, otherwise cracking may occur. Additives can be included in the screed mix to allow the drying time to be reduced. Calcium sulphate screeds can be force dried, using the underfloor heating, after 7 days.

	All types of screed should have the underfloor heating run through a heating/cooling cycle before floor coverings of any type are installed.		All types of screed should have the underfloor heating run through a heating/cooling cycle before floor coverings of any type are installed.
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	Most screeds are made from a 1:3 to 1:4.5 ratio of cement to sand. Enhanced screeds include additives to improve the properties of the standard screed. This can allow for faster drying times and extra strength if required.		Most screeds are made from a 1:3 to 1:4.5 ratio of cement to sand. Enhanced screeds include additives to improve the properties of the standard screed. This can allow for faster drying times and extra strength if required.

−	Manufacturers also offer self-compacting screeds that can be pumped through a delivery hose and levelled with a dappling bar. The majority of these screeds are anhydrite compounds based on a calcium sulphate binder. Large areas can be covered more quickly, however, care must be taken to ensure this type of screed dries completely. Calcium ~~Sulphate~~ screeds cannot be laid to a fall and are not suitable for permanently wet areas such as wet rooms, saunas, steam rooms and swimming pool surrounds.	+	Manufacturers also offer self-compacting screeds that can be pumped through a delivery hose and levelled with a dappling bar. The majority of these screeds are anhydrite compounds based on a calcium sulphate binder. Large areas can be covered more quickly, however, care must be taken to ensure this type of screed dries completely. Calcium sulphate screeds cannot be laid to a fall and are not suitable for permanently wet areas such as wet rooms, saunas, steam rooms and swimming pool surrounds.

	All screeds expand and contract to some degree so large areas need to have expansion joints or crack inducer cuts in the screed to allow movement without cracking.		All screeds expand and contract to some degree so large areas need to have expansion joints or crack inducer cuts in the screed to allow movement without cracking.

−	~~= Find out more =~~	+	= Related articles on Designing Buildings Wiki =
−		+
−	=== Related articles on Designing Buildings Wiki ===	+

	* Aggregate.		* Aggregate.
Line 62:		Line 62:
	* Flooring.		* Flooring.
	* Grout.		* Grout.
		+	* Harl.
	* Insulation.		* Insulation.
	* Lath and plaster.		* Lath and plaster.

Designing Buildings at 12:48, 26 May 2018

2018-05-26T12:48:06Z

← Older revision		Revision as of 12:48, 26 May 2018
Line 40:		Line 40:

	All types of screed should have the underfloor heating run through a heating/cooling cycle before floor coverings of any type are installed.		All types of screed should have the underfloor heating run through a heating/cooling cycle before floor coverings of any type are installed.
−
−

	= Composition of screed =		= Composition of screed =
Line 76:		Line 74:
	* Stucco.		* Stucco.
	* Substructure.		* Substructure.
		+	* Tiled floors with underfloor heating: A guide to minimising and repairing cracking.
	* Underfloor heating.		* Underfloor heating.
	* Wet trades.		* Wet trades.

Kevflow60 at 15:08, 26 October 2017

2017-10-26T15:08:54Z

← Older revision		Revision as of 15:08, 26 October 2017
Line 1:		Line 1:
	= Introduction =		= Introduction =

−	Generally, concrete floors, other than those in buildings such as warehouses which may be left exposed, are covered with a screed layer. This is a layer of material, usually a sand and cement mix (sometimes with added fibres and other additives), generally laid to prepare for the installation of a floor covering, such as tiles, carpet or timber. Standards for screeds are set out in BS 8204, Screeds, bases and in-situ floorings.	+	Generally, concrete floors, other than those in buildings such as warehouses which may be left exposed, are covered with a screed layer. This is a layer of material, usually a sand and cement mix (sometimes with added fibres and other additives), or a proprietary flowing screed. Screeds are generally laid to prepare for the installation of a floor covering, such as tiles, carpet or timber. Standards for screeds are set out in BS 8204, Screeds, bases and in-situ floorings.

	The specification of screeds will vary depending on the requirement for:		The specification of screeds will vary depending on the requirement for:
Line 31:		Line 31:
	=== Flow / Liquid Screed ===		=== Flow / Liquid Screed ===

−	Liquid flow screed is fast becoming the industry standard in floor screeds. This type of floor is also referred to as self compacting screed or a calcium sulphate screed. Simple in its preparation this new form of flow screed is suitable for light ~~domestic use~~ in ~~under~~ 24-48 hours after installation.	+	Liquid flow screed is fast becoming the industry standard in floor screeds. This type of floor is also referred to as self compacting screed or a calcium sulphate screed. Simple in its preparation this new form of flow screed is suitable for light foot traffic in 24-48 hours. Partitions can be installed and/or the screed can be loaded out 7 days after installation.

	=== Screed over underfloor heating ===		=== Screed over underfloor heating ===

Kevflow60 at 15:03, 26 October 2017

2017-10-26T15:03:30Z

← Older revision		Revision as of 15:03, 26 October 2017
Line 47:		Line 47:
	Most screeds are made from a 1:3 to 1:4.5 ratio of cement to sand. Enhanced screeds include additives to improve the properties of the standard screed. This can allow for faster drying times and extra strength if required.		Most screeds are made from a 1:3 to 1:4.5 ratio of cement to sand. Enhanced screeds include additives to improve the properties of the standard screed. This can allow for faster drying times and extra strength if required.

−	Manufacturers also offer self-~~leveling~~ screeds that can be pumped through a delivery hose and ~~leveled~~ with a dappling bar. The majority of these screeds are anhydrite compounds based on a calcium ~~sulphite~~ binder. Large areas can be covered more quickly, however, care must be taken to ensure this type of screed dries completely ~~and it can~~ be ~~susceptible~~ to ~~water damage, so is~~ not ~~the most~~ suitable ~~screed~~ for ~~external or~~ permanently wet areas.	+	Manufacturers also offer self-compacting screeds that can be pumped through a delivery hose and levelled with a dappling bar. The majority of these screeds are anhydrite compounds based on a calcium sulphate binder. Large areas can be covered more quickly, however, care must be taken to ensure this type of screed dries completely. Calcium Sulphate screeds cannot be laid to a fall and are not suitable for permanently wet areas such as wet rooms, saunas, steam rooms and swimming pool surrounds.

	All screeds expand and contract to some degree so large areas need to have expansion joints or crack inducer cuts in the screed to allow movement without cracking.		All screeds expand and contract to some degree so large areas need to have expansion joints or crack inducer cuts in the screed to allow movement without cracking.

213.123.75.36 at 14:42, 26 October 2017

2017-10-26T14:42:38Z

← Older revision		Revision as of 14:42, 26 October 2017
Line 17:		Line 17:
	=== Bonded screed ===		=== Bonded screed ===

−	The screed layer is fully bonded to the substrate using a primer or bonding agent. This method is commonly used for thinner screeds where heavy loading is expected and where there is not enough space available to lay an unbonded screed. The optimum thickness of a sand and cement bonded screed is generally in the region of 25-40mm. Care must be taken during the laying process to ensure de-bonding does not occur as this can lead to instability and ultimately, the screed may fail.	+	The screed layer is fully bonded to the substrate using a primer or bonding agent. This method is commonly used for thinner screeds where heavy loading is expected and where there is not enough space available to lay an unbonded screed. The optimum thickness of a sand and cement bonded screed is generally in the region of 25-40mm. Some calcium sulphate flowing screeds can be laid at a minimum depth of 12mm. Care must be taken during the laying process to ensure de-bonding does not occur as this can lead to instability and ultimately, the screed may fail.

	=== Unbonded screed ===		=== Unbonded screed ===

−	Instead of being bonded directly to the base, unbonded screeds are applied over a damp proof membrane (DPM) laid on top of the concrete base. The minimum thickness of an unbonded screed is usually in the region of 50mm. The advantage of an unbonded screed is that the flooring is not in direct contact with the main structure and so the potential impacts of settlement or shrinkage can be less problematic. The DPM creates a barrier preventing damp rising from the substrate.	+	Instead of being bonded directly to the base, unbonded screeds are applied over a damp proof membrane (DPM) laid on top of the concrete base. The minimum thickness of an unbonded sand and cement screed is usually in the region of 50mm. Calcium Sulphate screeds can be laid unbonded at a minimum depth of 30 mm. The advantage of an unbonded screed is that the flooring is not in direct contact with the main structure and so the potential impacts of settlement or shrinkage can be less problematic. The DPM creates a barrier preventing damp rising from the substrate.

−	However, this type of screed can be more prone to curling if dried quickly. Curling is a vertical distortion of the edges due to temperature differences or moisture content throughout the thickness of the screed. This can be prevented by adhering to minimum specified thicknesses and allowing for slow drying.	+	However, this type of screed can be more prone to curling if dried quickly. Curling is a vertical distortion of the edges due to temperature differences or moisture content throughout the thickness of the screed. This can be prevented by adhering to minimum specified thicknesses and allowing for slow drying. Calcium Sulphate screeds are not prone to curling due to their lower rates of shrinkage compared to sand and cement screeds.

	=== Floating screed ===		=== Floating screed ===

−	The screed is laid on top of insulation to create a thermally efficient floor. Floating screeds are commonly used where underfloor heating systems are provided or thermal or acoustic insulation is required. Floating screeds generally have a thickness greater than 65 mm for lightly-loaded floors and 75 mm for more heavily-loaded floors.	+	The screed is laid on top of insulation to create a thermally efficient floor. Floating screeds are commonly used where underfloor heating systems are provided or thermal or acoustic insulation is required. Floating sand and cement screeds generally have a thickness greater than 65 mm for lightly-loaded floors and 75 mm for more heavily-loaded floors. Calcium Sulphate floating screeds can be installed at 35 mm depth for domestic use or 40 mm for commercial use.

	=== Flow / Liquid Screed ===		=== Flow / Liquid Screed ===

−	Liquid flow screed is fast becoming the industry standard in floor screeds. This type of floor is also referred to as self ~~leveling~~ screed or a calcium sulphate screed. Simple in its preparation this new form of flow screed is suitable for light domestic use in under 24-48 hours after installation.	+	Liquid flow screed is fast becoming the industry standard in floor screeds. This type of floor is also referred to as self compacting screed or a calcium sulphate screed. Simple in its preparation this new form of flow screed is suitable for light domestic use in under 24-48 hours after installation.

	=== Screed over underfloor heating ===		=== Screed over underfloor heating ===
Line 37:		Line 37:
	This is where the floating screed layer is installed over underfloor heating pipes or insulation. The screed serves to conduct the heat evenly across the floor surface, avoiding hot or cold spots, and helps to retain heat for longer. In order that heat propagates only in the required direction of the room to be heated or cooled, the elements are inserted above insulating panels. Sand cement screeds require a minimum thickness of 65 mm, with the ideal being between 65-75 mm.		This is where the floating screed layer is installed over underfloor heating pipes or insulation. The screed serves to conduct the heat evenly across the floor surface, avoiding hot or cold spots, and helps to retain heat for longer. In order that heat propagates only in the required direction of the room to be heated or cooled, the elements are inserted above insulating panels. Sand cement screeds require a minimum thickness of 65 mm, with the ideal being between 65-75 mm.

−	Where fibres are added or when using anhydrite screeds the minimum thickness may be reduced to 50 mm. Care must be exercised in allowing adequate drying time (usually around 21 days) before incrementally turning on the heating system, otherwise cracking may occur. Additives can be included in the screed mix to allow the drying time to be reduced.	+	Where fibres are added or when using anhydrite screeds the minimum thickness may be reduced to 50 mm. Some specialised calcium sulphate screeds can be installed with only 20 mm cover to the heating pipes, giving screed depths of less than 40 mm Care must be exercised in allowing adequate drying time (usually around 21 days) before incrementally turning on the heating system, otherwise cracking may occur. Additives can be included in the screed mix to allow the drying time to be reduced. Calcium sulphate screeds can be force dried, using the underfloor heating, after 7 days.
		+
		+	All types of screed should have the underfloor heating run through a heating/cooling cycle before floor coverings of any type are installed.
		+
		+

	= Composition of screed =		= Composition of screed =

Editor at 15:49, 29 August 2017

2017-08-29T15:49:48Z

← Older revision		Revision as of 15:49, 29 August 2017
Line 73:		Line 73:
	* Substructure.		* Substructure.
	* Underfloor heating.		* Underfloor heating.
		+	* Wet trades.

	=== External references ===		=== External references ===

Editor at 12:12, 3 July 2017

2017-07-03T12:12:00Z

← Older revision		Revision as of 12:12, 3 July 2017
Line 68:		Line 68:
	* Reinforced concrete.		* Reinforced concrete.
	* Rendering.		* Rendering.
		+	* Sealant.
	* Separating floor.		* Separating floor.
	* Stucco.		* Stucco.