Inverted roof - Revision history

Designing Buildings at 05:53, 5 May 2023

2023-05-05T05:53:04Z

← Older revision		Revision as of 05:53, 5 May 2023
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	For a case study of an inverted roof defect, see Inverted roof defect - case study.		For a case study of an inverted roof defect, see Inverted roof defect - case study.

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

	* Cold roof.		* Cold roof.

Designing Buildings at 06:07, 5 October 2020

2020-10-05T06:07:37Z

← Older revision		Revision as of 06:07, 5 October 2020
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	* Warm roof.		* Warm roof.

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Designing Buildings at 09:17, 13 November 2017

2017-11-13T09:17:06Z

← Older revision		Revision as of 09:17, 13 November 2017
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−	~~When designing~~ a ~~flat~~ roof ~~construction~~, it is ~~important that~~ the ~~designer ensures~~ the ~~appropriate provision of~~ insulation ~~to control both condensation and heat loss through the roof construction~~.	+	An inverted roof, also referred to as a ‘protected membrane’ or ‘upside down’ roof, is form of flat roof in which the waterproofing layer is beneath the thermal insulation rather than above it.

−	~~An inverted roof, also referred to as~~ a ~~‘protected membrane’ or ‘upside down’~~ roof, ~~is where~~ the ~~waterproofing layer is beneath~~ the ~~thermal~~ insulation ~~layer instead of above~~ it~~. This means that the temperature within the roof void~~ is ~~closer to that of the building’s interior, without a vapour control layer being required as with a warm roof~~.	+	The waterproofing layer is typically a liquid-applied membrane above a concrete roof slab, with insulation boards laid over the top, weighted down with either paving slabs or gravel ballast to protect against wind uplift and flotation. Rainwater percolates down through and between the insulation boards to the membrane where it is drained away through rainwater outlets.

−	~~The waterproofing layer~~ is ~~typically a liquid-applied~~ membrane, and ~~insulation boards are laid loose over~~ the ~~top~~, ~~weighted down with either paving slabs or gravel ballast to protect against wind uplift~~ and ~~flotation~~.	+	One of the main benefits of the inverted roof method is that the membrane is protected by the insulation from the expansion and contraction caused by weather fluctuations, such as frost and solar radiation. It is also protected from damage by traffic on the roof, such as people walking, the movement of equipment and so on.

−	The inverted roof method tends to be used only for concrete support structures within flat roofs, as the ballast that is required to restrain the insulation applies additional weight loading to the system.	+	When calculating the U-value of the roof, consideration must be given to the fact that the insulation is likely to be wet a lot of the time, with some moisture trapped beneath the boards. This can create the risk of condensation occurring within the build-up of the roof, as the temperature of the membrane can be below the dew point. However, once the roof deck (and the membrane) warms up, the condensation will be able to evaporate. Problems can occur if the accumulation of condensation persists.
−		+
−	One of the main benefits of using the inverted roof method is that the membrane is protected by the insulation from the expansion and contraction caused by weather fluctuations, such as frost and UV exposure. The ballast percolates rainwater down through and between the insulation boards to the membrane where it is drained away through rainwater outlets.	+
−		+
−	When calculating the U-value of the roof, it must be ~~considered~~ that the insulation is ~~expected~~ to be wet ~~for most~~ of ~~its lifetime~~, ~~since capillary action often traps~~ some moisture beneath the boards. This can create the risk of condensation occurring within the build-up of the roof, as the temperature of the membrane can be below the dew point. ~~Once~~ the roof deck (and the membrane) warms up, the condensation will be able to evaporate. Problems can occur if the accumulation of condensation persists.	+

	For more information, see Specifying insulation for inverted roofs.		For more information, see Specifying insulation for inverted roofs.
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	* Warm roof.		* Warm roof.

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Editor at 14:16, 12 November 2017

2017-11-12T14:16:02Z

← Older revision		Revision as of 14:16, 12 November 2017
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	For more information, see Specifying insulation for inverted roofs.		For more information, see Specifying insulation for inverted roofs.
		+
		+	For a case study of an inverted roof defect, see Inverted roof defect - case study.

	= Find out more =		= Find out more =
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	* Flat roof defects.		* Flat roof defects.
	* Interstitial condensation.		* Interstitial condensation.
		+	* Inverted roof defect - case study.
	* Roofing defects.		* Roofing defects.
	* Specifying insulation for inverted roofs.		* Specifying insulation for inverted roofs.

Editor: Created page with "When designing a flat roof construction, it is important that the designer ensures the appropriate provision of insulation to control both condensation and heat loss through the ..."

2017-11-12T13:47:28Z

Created page with "When designing a flat roof construction, it is important that the designer ensures the appropriate provision of insulation to control both condensation and heat loss through the ..."

New page

When designing a flat roof construction, it is important that the designer ensures the appropriate provision of insulation to control both condensation and heat loss through the roof construction.

An inverted roof, also referred to as a ‘protected membrane’ or ‘upside down’ roof, is where the waterproofing layer is beneath the thermal insulation layer instead of above it. This means that the temperature within the roof void is closer to that of the building’s interior, without a vapour control layer being required as with a warm roof.

The waterproofing layer is typically a liquid-applied membrane, and insulation boards are laid loose over the top, weighted down with either paving slabs or gravel ballast to protect against wind uplift and flotation.

The inverted roof method tends to be used only for concrete support structures within flat roofs, as the ballast that is required to restrain the insulation applies additional weight loading to the system.

One of the main benefits of using the inverted roof method is that the membrane is protected by the insulation from the expansion and contraction caused by weather fluctuations, such as frost and UV exposure. The ballast percolates rainwater down through and between the insulation boards to the membrane where it is drained away through rainwater outlets.

When calculating the U-value of the roof, it must be considered that the insulation is expected to be wet for most of its lifetime, since capillary action often traps some moisture beneath the boards. This can create the risk of condensation occurring within the build-up of the roof, as the temperature of the membrane can be below the dew point. Once the roof deck (and the membrane) warms up, the condensation will be able to evaporate. Problems can occur if the accumulation of condensation persists.

For more information, see Specifying insulation for inverted roofs.

= Find out more =

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

* Cold roof.
* Condensation in buildings.
* Domestic roofs.
* Flat roof.
* Flat roof defects.
* Interstitial condensation.
* Roofing defects.
* Specifying insulation for inverted roofs.
* Stack effect.
* Thermal bridging in buildings.
* Thermal comfort.
* Warm roof.

[[Category:Construction_techniques]] [[Category:Products_/_components]]