Signs and solutions for underfloor ventilation problems

Signs and solutions for underfloor ventilation problems

As suppliers to the trade for many years, Manthorpe have a strong understanding in preventing problems that can be caused by poor underfloor ventilation. This guide will help you to identify the signs of possible problems and explains the different purposes and uses of Manthorpe’s extensive underfloor ventilation product range.

Why is underfloor ventilation required?
Where is underfloor ventilation required?
What are typical problems associated with underfloor ventilation?
What are the signs of underfloor ventilation problems?
What types of underfloor ventilation are available?
Which underfloor ventilation products do Manthorpe supply?
How can I get hold of Manthorpe underfloor ventilation products?

 Why is underfloor ventilation required?

Underfloor voids beneath a suspended floor, found in many recent and modern builds, provide an ideal opportunity for moisture and condensation to build up and resulting in expensive damage to a property. They can also harbour dangerous ground gases such as methane and radon, which can be extremely harmful to occupants over time. It is therefore vital that underfloor ventilation is employed to both remove these dangers and circulate fresh air into these voids.

Build-up of moisture can also be a result of flooding within the underfloor void slowly drying out, which is improved through added ventilation to the void.

Because of the severity of the possible consequences of these threats, published standards (NHBC Standards 5.2) and relevant building regulations address all aspects of underfloor ventilation including site preparation, required ventilation calculation and the types of vents and grilles to be used in various circumstances. Therefore, whilst poor underfloor ventilation issues can have serious consequences, the extensive detail in the regulations and guidance should ensure none of these potential problems ever arise.

 Where is underfloor ventilation required?

Underfloor ventilation is required for both timber and concrete suspended floors and the building regulations approved documents state the positioning, frequency and airflow according to the volume of the underfloor space in question. However, as the industry and the world in general has become more energy-conscious and regulations have been adjusted to make homes and properties far more sustainable and energy efficient, there has been a knock-on effect for standards and products on other areas. For example, increased depth of insulation in suspended floors and increasing wall cavity spaces can result in a depth of 6-7 brick courses between an air brick and the underfloor void and a wall thickness of over 350mm from the outer face of the external leaf.

Therefore, underfloor ventilation is not only critical to the long life of a property and the wellbeing of its occupants, but it also needs to adapt to changing requirements and regulations in order to remain as efficient and sustainable as possible.

 What are typical problems associated with underfloor ventilation?

Underfloor ventilation is required for two reasons; the removal of moisture to prevent the build-up of condensation and the dilution and evacuation of potentially harmful ground gases. Both of these are achieved through the use of sufficient and directed flow of fresh air from the outside. Modern design of vents encourages cross flow ventilation when vents are placed on opposing sides.

Failure to remove damp air from an underfloor void can lead to the accumulation of condensation and damage key components of the structure.

Concrete suspended floors are not immune from condensation problems. Concrete, by its nature, is very porous and condensation can be drawn up through the concrete through capillary action. On reaching the top of the concrete, the condensation provides an ideal breeding ground for mould and all the associated problems this brings for flooring.

Whilst the harm caused by ground gases such as methane and radon takes longer to manifest, it is a far more serious problem since it can directly affect the health of occupants, far more valuable than any property. Ensuring correct underfloor ventilation is in place prevents this chronic damage from the outset and for the building’s lifetime.

 What are the signs of an underfloor ventilation problem?

You may notice a musty smell in a room or property that has been affected by an underfloor ventilation problem but that is not a reliable measure and could be an indication of airflow problems in other areas such as walls. For many people the first indication might be creaking and sagging; a sign that the integrity of the underlying timber beans has been compromised by rot caused by the build-up of condensation

All of this and the associated cost and inconvenience of putting everything right can be avoided by use of the correct and appropriate products and materials in the first place and ensuring that air bricks do not become blocked. Whatever the type of build, it’s vital to prevent and keep an eye out for floor damp-related issues.

 What types of underfloor ventilation are available?

All underfloor ventilation is achieved by essentially the same solution; a, usually, rigid conduit leading from the underfloor void to the exterior, finished with an air brick or grille depending on the required external finish. Where necessary, a flexible or rigid pipe might be used instead. Sleeper walls and partitions should also be constructed with sufficient openings to ensure adequate through ventilation.

These conduits often take the form of a periscope shape with the horizontal sections interfacing with the underfloor void and the exterior and the vertical section linking the two horizontal sections. The vertical section might be fixed or telescopic to cater for different numbers of courses within the property’s construction.

Recent changes in regulations requiring additional insulation within suspended floors have led to the need for vents to cover a greater number of brick courses, sometimes up to eight. Manthorpe manufactures both telescopic vents and extensions sleeves to ensure that all scenarios are covered.

The key factors in getting underfloor ventilation right are the positioning and number of vents to ensure that the airflow can circulate thoroughly in the underfloor void while at the same time meeting insulation and efficiency requirements. Formulae within the relevant building regulations approved documents allow easy calculation of the required amount of airflow for any given void as well as the number, spacing and positioning of the vents.

  Which underfloor ventilation products do Manthorpe supply?

Manthorpe produces a wide range of underfloor ventilation products and accessories for both new build and refurbishment projects.

G960 : Telescopic Underfloor Vent
Once installed, this product creates an unobstructed, clear passage for fresh air to enter the underfloor void of a suspended floor structure. Used in conjunction with our G930 Airbrick, the product provides 6,450mm² of airflow to a void. Used as a standalone, it allows for a vertical extension of 3-5 courses (215mm-365mm) and can be used with our G961 Extension Sleeve to increase both the vertical and horizontal length of the product if a detail requires this.

G965 : Dual Extended Underfloor Vent
Used for the same purpose as our G960 product, our G965 provides the same amount of airflow to an underfloor void, however due to progression within the industry the G965 offers a vertical extension of 5-8 courses (318mm-575mm) and a horizontal span of 360mm (including our G930 Airbrick).

G966 : Stacked Underfloor Vent
Our G966 Stacked Underfloor Vent was designed to provide the underfloor void of a suspended floor whilst giving the house builder more opportunity and space to create an accessible opening into the property. The current and future requirements of Building
Regulations Approved Document M for accessibility into and around a domestic property, has led to the increasing demand for a double, stacked underfloor ventilator. Each ventilator provides 12,900mm² of airflow into an underfloor void.

G961 : Extension Sleeve
Our G961 Extension Sleeve allows for either the G960 or the G965 to be extended horizontally and vertically by 2 vertical brick courses and 150mm in the horizontal.

G935 : Cavity Sleeve
Our G935 Cavity Sleeve can be used with a G930 Airbrick alone to directly bridge across a cavity wall into an underfloor void.
It can also be used to extend the front of either our G960 or G965 products, if the external masonry leaf of the property is deeper than 102mm (from the front face of the external leaf to the back face of the external leaf).
Multiple G935 products can be joined together, creating a longer sleeve if required. It can also be trimmed down to suit.

G962 : Remote Void Vent
Our G962 Remote Void Vent can be used to connect either our G930 Airbrick to a 4inch pipe, or one of our telescopic vents to a 4inch pipe. This makes the product ideal for ducting airflow under a cast concrete floor which are commonly found in extensions to existing buildings.

 How can I get hold of Manthorpe underfloor ventilation products?

Manthorpe’s range of underfloor ventilation products is available through a wide selection of merchants. A list of stockists is available on this site, but should you have any further questions on stockist locations, or underfloor ventilation in general, please get in touch by phone, email or completing our contact form.