Cavity wall - Revision history

Designing Buildings at 07:43, 24 August 2026

2026-08-24T07:43:36Z

← Older revision		Revision as of 07:43, 24 August 2026
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	= History =		= History =

−	A cavity wall is a wall formed by an inner skin and an outer skin of masonry (sometimes referred to as ~~‘leaves’~~ or ~~‘wythes’~~ if they are a single unit wide), connected by ties, but separated by a cavity. The masonry is formed by units such as brick, stone or block. Very generally, if the external walls of a building are less than 30 cm thick, then they are unlikely to include a cavity.	+	A cavity wall is a wall formed by an inner skin and an outer skin of masonry (sometimes referred to as 'leaves' or 'wythes' if they are a single unit wide), connected by ties, but separated by a cavity. The masonry is formed by units such as brick, stone or block. Very generally, if the external walls of a building are less than 30 cm thick, then they are unlikely to include a cavity.

	Cavity walls existed in Greek and Roman times, but only developed as a component of more recent construction in the 18th and 19th centuries. Even during this time, they were very rare, and generally involved two skins of masonry bonded by headers spanning across the cavity. The use of metal ties to connect the two skins only emerged in the second half of the 19th century and then became more common towards the beginning of the 20th century.		Cavity walls existed in Greek and Roman times, but only developed as a component of more recent construction in the 18th and 19th centuries. Even during this time, they were very rare, and generally involved two skins of masonry bonded by headers spanning across the cavity. The use of metal ties to connect the two skins only emerged in the second half of the 19th century and then became more common towards the beginning of the 20th century.
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	In the UK, most new, external masonry walls have been cavity walls since the 1920s.		In the UK, most new, external masonry walls have been cavity walls since the 1920s.

−	[[File:~~Cavity_wall.jpg\|link=File:Cavity_wall~~.jpg]]	+	[[File:Cavity wall.jpg]]

	= Penetrating damp =		= Penetrating damp =
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	* At the bottom of a wall, if the cavity does not extend 225 mm below the damp-proof course.		* At the bottom of a wall, if the cavity does not extend 225 mm below the damp-proof course.

−	[[File:~~Cavity_tray.jpg\|link=File:Cavity_tray~~.jpg]]	+	[[File:Cavity tray.jpg]]

	Cavities are ventilated to ensure that any accumulating moisture is able to evaporate and vent to the outside.		Cavities are ventilated to ensure that any accumulating moisture is able to evaporate and vent to the outside.
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	This means that older buildings tend to transfer more heat between the inside and outside and so can be colder in the winter, hotter in the summer, can suffer condensation, can be expensive to run, are high emitters of carbon and may not provide very good levels of thermal comfort.		This means that older buildings tend to transfer more heat between the inside and outside and so can be colder in the winter, hotter in the summer, can suffer condensation, can be expensive to run, are high emitters of carbon and may not provide very good levels of thermal comfort.

−	Typically the U-values (a measure thermal conductance) of walls are:	+	Typically the U-values (a measure of thermal conductance) of walls are:

−	* Solid brick wall 2.0 W/~~m2K~~.	+	* Solid brick wall: 2.0 W/(m²K).
−	* Cavity wall with no insulation 1.5 W/~~m2K~~.	+	* Cavity wall with no insulation: 1.5 W/(m²K).
−	* Insulated cavity wall 0.3 W/~~m2K or less~~.	+	* Insulated cavity wall: 0.18 to 0.3 W/(m²K), depending on the thickness and specification of the insulation.

−	The approved documents to the building regulations set limiting fabric standards for the elements of buildings. These are area-weighted averages that those elements may not fall below, and generally, to comply with the building regulations, fabric performance will need to be significantly better than these limits. ~~The~~ limiting U-value for walls in new dwellings ~~is 0.3 W/m2K~~ and ~~for~~ buildings other than dwellings is 0.35 W/~~m2K. Where~~ new thermal elements are constructed, such as in ~~a new~~ extension, they should be at least 0.28 W/~~m2K~~.	+	The approved documents to the building regulations set limiting fabric standards for the elements of buildings. These are area-weighted averages that those elements may not fall below, and generally, to comply with the building regulations, fabric performance will need to be significantly better than these limits. Under the current (2021 edition, incorporating 2023 amendments) Approved Document L, the limiting U-value for walls in new dwellings and in buildings other than dwellings is 0.26 W/(m²K); where new thermal elements are constructed, such as in an extension to an existing building, they should be at least 0.18 W/(m²K).

	Insulation is generally fixed to the external face of the internal skin of the cavity wall. This allows the remainder of the cavity to be ventilated without significant heat loss. However, in some cases, particularly where insulation is retrofitted, the entire cavity is filled. Great care must be taken in this case to ensure that a path is not created for the penetration of moisture between the outside and inside.		Insulation is generally fixed to the external face of the internal skin of the cavity wall. This allows the remainder of the cavity to be ventilated without significant heat loss. However, in some cases, particularly where insulation is retrofitted, the entire cavity is filled. Great care must be taken in this case to ensure that a path is not created for the penetration of moisture between the outside and inside.

−	[[File:~~Cavity_wall_insulation.jpg\|link=File:Cavity_wall_insulation~~.jpg]]	+	[[File:Cavity wall insulation.jpg]]

−	The exact dimensions required to satisfy Part L of the building regulations will depend on the type of building and the thermal conductivity of the materials selected. Typically, with the correct selection of materials, a 102.5 mm external skin, 100 mm cavity (either filled or part-filled) and 100 mm internal skin, plastered on its internal face can be made to comply with ~~part~~ L.	+	The exact dimensions required to satisfy Part L of the building regulations will depend on the type of building and the thermal conductivity of the materials selected. Typically, with the correct selection of materials, a 102.5 mm external skin, 100 mm cavity (either filled or part-filled) and 100 mm internal skin, plastered on its internal face can be made to comply with Part L.

−	Cavity walls that are not insulated can have insulation retrofitted by drilling small holes at regular intervals in the external skin and then ~~‘blowing’~~ or ~~‘injecting’~~ insulation into the cavity from the outside. Typically, water-repellent insulation is used such as expanded polystyrene (EPS) beads combined with a binding agent, or urea formaldehyde (UF) foam insulation. The drilled holes are then filled to match the existing finish. See Cavity wall insulation for more information.	+	Cavity walls that are not insulated can have insulation retrofitted by drilling small holes at regular intervals in the external skin and then 'blowing' or 'injecting' insulation into the cavity from the outside. Typically, water-repellent insulation is used such as expanded polystyrene (EPS) beads combined with a binding agent, or urea formaldehyde (UF) foam insulation. The drilled holes are then filled to match the existing finish. Since 30 March 2025, retrofit cavity wall insulation carried out under government-backed schemes such as the Energy Company Obligation (ECO) and the Warm Homes programme must be delivered in accordance with the updated PAS 2035:2023 standard, which requires a whole-house, fabric-first assessment and a qualified retrofit coordinator to oversee the works; the standard was introduced in response to widespread defects, including damp and mould, found in earlier retrofit installations. See Cavity wall insulation for more information.

	= Vapour barrier =		= Vapour barrier =

−	As warm, moist internal air permeates through the structure of the wall towards the outside, it will tend to cool. When it reaches its ~~‘dew point’~~ temperature, moisture will begin to condense as water. If this happens within the structure of the wall, this is known as interstitial condensation, and if this occurs within the inner skin of the wall, this can cause problems such as:	+	As warm, moist internal air permeates through the structure of the wall towards the outside, it will tend to cool. When it reaches its 'dew point' temperature, moisture will begin to condense as water. If this happens within the structure of the wall, this is known as interstitial condensation, and if this occurs within the inner skin of the wall, this can cause problems such as:

	* Mould growth, migration of salts, mildew and staining.		* Mould growth, migration of salts, mildew and staining.
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	* Barrier wall system.		* Barrier wall system.
	* Brick.		* Brick.
−	* Bricklayer.
	* Building damp-free cavity walls.		* Building damp-free cavity walls.
−	* Bullseye window.
	* Cavity wall insulation.		* Cavity wall insulation.
	* Cavity tray.		* Cavity tray.
	* Cold bridge.		* Cold bridge.
−	* Coping and capping
−	* Crosswall construction.
	* Damp proof course.		* Damp proof course.
	* Defects in brickwork.		* Defects in brickwork.
−	* Defects in stonework.
	* Dew point.		* Dew point.
−	* How to lay bricks.
	* Insulation.		* Insulation.
	* Interstitial condensation.		* Interstitial condensation.
	* Masonry.		* Masonry.
−	* Parapet.
−	* Pistol brick.
	* Preventing wall collapse.		* Preventing wall collapse.
	* Rainscreen.		* Rainscreen.
	* Solid wall insulation.		* Solid wall insulation.
	* The cavity wall real performance question.		* The cavity wall real performance question.
−	* Treating brickwork with sealant or water repellent.
−	* Types of brick.
−	* Types of brick bonding.
	* Vapour barrier.		* Vapour barrier.
−	* Wall plate.
	* Wall ties.		* Wall ties.
	* Wall tie failure.		* Wall tie failure.
−	* Wall types.

	[[Category:DCN_Definition]] [[Category:DCN_Guidance]] [[Category:DCN_Product_Knowledge]]		[[Category:DCN_Definition]] [[Category:DCN_Guidance]] [[Category:DCN_Product_Knowledge]]

Designing Buildings at 05:56, 1 April 2022

2022-04-01T05:56:58Z

← Older revision		Revision as of 05:56, 1 April 2022
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	* Wall types.		* Wall types.

−	[[Category:DCN_Definition]] [[Category:DCN_Guidance]] [[Category:DCN_Product_Knowledge~~]] [[Category:Products_/_components~~]]	+	[[Category:DCN_Definition]] [[Category:DCN_Guidance]] [[Category:DCN_Product_Knowledge]]

Editor at 12:30, 7 February 2022

2022-02-07T12:30:44Z

← Older revision		Revision as of 12:30, 7 February 2022
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	To prevent this, Vapour Control Layers (VCL) or vapour barriers are positioned on the warm side of the cavity insulation, (i.e. between the insulation and the inner masonry skin), preventing the warm moist air from penetrating to a point where it might reach its dew point temperature.		To prevent this, Vapour Control Layers (VCL) or vapour barriers are positioned on the warm side of the cavity insulation, (i.e. between the insulation and the inner masonry skin), preventing the warm moist air from penetrating to a point where it might reach its dew point temperature.

−	= Related articles on Designing Buildings ~~Wiki~~ =	+	= Related articles on Designing Buildings =

	* Accredited construction details ACDs.		* Accredited construction details ACDs.
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	* Rainscreen.		* Rainscreen.
	* Solid wall insulation.		* Solid wall insulation.
		+	* The cavity wall real performance question.
	* Treating brickwork with sealant or water repellent.		* Treating brickwork with sealant or water repellent.
	* Types of brick.		* Types of brick.

Designing Buildings: Reverted edits by 106.77.133.189 (talk) to last revision by Designing Buildings

2021-05-29T10:20:14Z

Reverted edits by 106.77.133.189 (talk) to last revision by Designing Buildings

← Older revision		Revision as of 10:20, 29 May 2021
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	* Vapour barrier.		* Vapour barrier.
	* Wall plate.		* Wall plate.
−	* ~~[https://civiconcepts.com/blog/cavity-wall~~ Wall ties.]	+	* Wall ties.
	* Wall tie failure.		* Wall tie failure.
	* Wall types.		* Wall types.

−	~~[[Category:Articles_needing_more_work]]~~ [[Category:DCN_Definition]] [[Category:DCN_Guidance]] [[Category:DCN_Product_Knowledge]] [[Category:Products_/_components]]	+	[[Category:DCN_Definition]] [[Category:DCN_Guidance]] [[Category:DCN_Product_Knowledge]] [[Category:Products_/_components]]

106.77.133.189 at 10:15, 29 May 2021

2021-05-29T10:15:10Z

← Older revision		Revision as of 10:15, 29 May 2021
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	* Vapour barrier.		* Vapour barrier.
	* Wall plate.		* Wall plate.
−	* Wall ties.	+	* [https://civiconcepts.com/blog/cavity-wall Wall ties.]
	* Wall tie failure.		* Wall tie failure.
	* Wall types.		* Wall types.

−	[[Category:DCN_Definition]] [[Category:DCN_Guidance]] [[Category:DCN_Product_Knowledge]] [[Category:Products_/_components]]	+	[[Category:Articles_needing_more_work]] [[Category:DCN_Definition]] [[Category:DCN_Guidance]] [[Category:DCN_Product_Knowledge]] [[Category:Products_/_components]]

Designing Buildings at 08:37, 12 May 2021

2021-05-12T08:37:50Z

← Older revision		Revision as of 08:37, 12 May 2021
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	To prevent this, Vapour Control Layers (VCL) or vapour barriers are positioned on the warm side of the cavity insulation, (i.e. between the insulation and the inner masonry skin), preventing the warm moist air from penetrating to a point where it might reach its dew point temperature.		To prevent this, Vapour Control Layers (VCL) or vapour barriers are positioned on the warm side of the cavity insulation, (i.e. between the insulation and the inner masonry skin), preventing the warm moist air from penetrating to a point where it might reach its dew point temperature.
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−	~~{{:Catnic_CTA_setup}}~~

	= Related articles on Designing Buildings Wiki =		= Related articles on Designing Buildings Wiki =

Designing Buildings at 09:10, 17 March 2021

2021-03-17T09:10:52Z

← Older revision		Revision as of 09:10, 17 March 2021
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	To prevent this, Vapour Control Layers (VCL) or vapour barriers are positioned on the warm side of the cavity insulation, (i.e. between the insulation and the inner masonry skin), preventing the warm moist air from penetrating to a point where it might reach its dew point temperature.		To prevent this, Vapour Control Layers (VCL) or vapour barriers are positioned on the warm side of the cavity insulation, (i.e. between the insulation and the inner masonry skin), preventing the warm moist air from penetrating to a point where it might reach its dew point temperature.
		+
		+	{{:Catnic_CTA_setup}}

	= Related articles on Designing Buildings Wiki =		= Related articles on Designing Buildings Wiki =

Designing Buildings at 10:40, 29 October 2020

2020-10-29T10:40:47Z

← Older revision		Revision as of 10:40, 29 October 2020
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	To prevent this, Vapour Control Layers (VCL) or vapour barriers are positioned on the warm side of the cavity insulation, (i.e. between the insulation and the inner masonry skin), preventing the warm moist air from penetrating to a point where it might reach its dew point temperature.		To prevent this, Vapour Control Layers (VCL) or vapour barriers are positioned on the warm side of the cavity insulation, (i.e. between the insulation and the inner masonry skin), preventing the warm moist air from penetrating to a point where it might reach its dew point temperature.
−
−	~~{{:IG_masonry_cta_setup}}~~

	= Related articles on Designing Buildings Wiki =		= Related articles on Designing Buildings Wiki =

Designing Buildings at 09:15, 18 September 2020

2020-09-18T09:15:44Z

← Older revision		Revision as of 09:15, 18 September 2020
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	To prevent this, Vapour Control Layers (VCL) or vapour barriers are positioned on the warm side of the cavity insulation, (i.e. between the insulation and the inner masonry skin), preventing the warm moist air from penetrating to a point where it might reach its dew point temperature.		To prevent this, Vapour Control Layers (VCL) or vapour barriers are positioned on the warm side of the cavity insulation, (i.e. between the insulation and the inner masonry skin), preventing the warm moist air from penetrating to a point where it might reach its dew point temperature.
		+
		+	{{:IG_masonry_cta_setup}}

	= Related articles on Designing Buildings Wiki =		= Related articles on Designing Buildings Wiki =

Designing Buildings at 09:00, 18 September 2020

2020-09-18T09:00:26Z

← Older revision		Revision as of 09:00, 18 September 2020
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	To prevent this, Vapour Control Layers (VCL) or vapour barriers are positioned on the warm side of the cavity insulation, (i.e. between the insulation and the inner masonry skin), preventing the warm moist air from penetrating to a point where it might reach its dew point temperature.		To prevent this, Vapour Control Layers (VCL) or vapour barriers are positioned on the warm side of the cavity insulation, (i.e. between the insulation and the inner masonry skin), preventing the warm moist air from penetrating to a point where it might reach its dew point temperature.
−
−	~~{{:Keystone_cta_setup}}~~

	= Related articles on Designing Buildings Wiki =		= Related articles on Designing Buildings Wiki =