Suspended Timber Floors Research Articles

Trends in Residential Building Materials in the State of Victoria

As the population in Victoria continues to grow, there has been a corresponding increase in building approvals across the State. Houses characterised as low-rise residential buildings often take the largest share of these approvals, with incessant residential building activities being driven by record low interest rates. Low-rise residential buildings comprise various building forms that use a number of specified construction materials to construct the building envelope and other structural and non-structural elements. As materials used for constructing residential building envelopes continue to evolve, these materials must be fit for purpose, and satisfy design criteria and performance requirements, while being aesthetically pleasing. This research analyses the trend in construction materials used in building envelopes of low-rise residential buildings using data from building permits issued between 1996 to 2019. The trend analysis shows that traditional double brick wall systems and suspended timber floors have reduced in popularity for houses built in the 21st century. The analysis also shows that brick veneer wall cladding systems built over slab-on-ground footings is the dominant construction form while the roof cladding material is influenced by geographical location. Insights from the data analysis indicate very little innovation has emerged in materials for residential building envelopes despite its crucial role in providing thermal comfort for inhabitants. Results from this research will serve as a basis to provide quantitative assessment of the trend in materials resource; provide insights about the impact of new building envelope products on existing industries; and perspectives on materials for future building envelopes.

Māori Councils Act 1900: suspending floors

A recent review of the evolution of sub-floor moisture management (Isaacs "Evolution of Sub-Floor Moisture Management Requirements" pp. 366-394) found the first New Zealand legislative requirement for raised floors was in 1902 in by-laws made under the Māori Councils Act 1900. No similar requirements have been found in contemporaneous European building by-laws until those recommended by the Department of Public Health, Hospitals and Charitable Aid in 1912, which dealt with suspended floor durability.
 Although the use of well-made, well-drained earth floors used in Māori housing in pre-European times was in some sectors of Māori society looked back on with nostalgia, the use of suspended timber floors provided a drier, if airier, and healthier option. The Young Māori Party, with the support of the government, created a model by-law with two approaches to raise sitting and/or sleeping above ground. These required either the construction of suspended floor, or the use of a couch or bedstead at least 1 ft (0.3m) above the ground. As well as the ability to fix a time limit for compliance, it also provided the ability to levy fines if the household refused or neglected to comply with the notice. There was little variation in the implementation of the model by-law in the 24 districts established under the Act over nine years (1901 to 1910), except for the raised floor requirement (and associated penalty for non-compliance) which was not implemented in seven (30%) districts. It is concluded that unlike the durability concern of European suspended floor building by-laws, the Māori District by-laws were solely concerned with improvement of the health of the occupants.

Old Suspended Timber Floors Flexurally-Strengthened with Different Structural Materials

The design of timber beams has strict limits when it comes to the Serviceability Limit States (SLS) either in short-term or in long-term deflections. In order to face this aspect efficiently, the increase of the cross section of the beams might be considered as a solution. However, the prohibitive increase of the costs associated to this solution or the change of the initial architecture design of the building, opens the opportunity to find new and more efficient solutions. In that way, the use of additional reinforcements to the timber beams may be seen as a promising solution because either new or old structures would keep always their original aesthetical aspect with no significant self-weight increase and improving their behaviour to short and long-term actions. Therefore, the current study is dedicated to the analysis of composite timber beams where Fiber Reinforcement Polymers (FRP), steel or stainless steel are used to improve the stiffness, strength and deflection behaviour of old suspended timber floors. An experimental program was conducted where old suspended timber floors reinforced with CFRP strips were subjected to 4-point bending tests. A simplify nonlinear numerical model was developed to simulate the bending behaviour of the specimens and several other cases with other reinforcement configurations and different structural materials were assumed. The numerical analysis herein presented also takes into account both Ultimate and Serviceability Limit States of the reinforced specimens.

Flexural Strengthening of Old Timber Floors with Laminated Carbon Fiber–Reinforced Polymers

AbstractA set of three old suspended timber floors were flexurally strengthened with carbon fiber–reinforced polymer (CFRP) strips in order to investigate the effectiveness of externally bonding FRP to their soffits. The specimens were from an old building and 740-mm-wide bands were transferred to the laboratory in order to be tested in a four-point bending test. One specimen was tested with no strengthening system and the results obtained were used as reference values for comparison with the specimens that were externally bonded and reinforced (EBR) with CFRP strips. Two similar EBR systems were studied: (1) keeping both ends of the CFRP strips free of any restriction (traditional technique), and (2) embedding both ends of the CFRP strips into the timber, thus providing a bonding anchorage of the strips (new technique). The installation of the new strengthening system comprises the opening of holes in the timber and the creation of a transition curve between the holes and the timber surface. This transit...

A comparative study of floor construction on sloping sites: an analysis of cumulative energy demand and greenhouse gas emissions

In order to make environmentally aware decisions, there is growing interest in the comparative energy and greenhouse gas (GHG) performance of competing construction methods. Little research has been done concerning competing ground floor construction methods, especially given different site variables, such as slope and soil type. A life cycle assessment approach was adopted to analyse environmental impacts, including cumulative energy demand and GHG emissions for detached housing construction in Australia. Data was drawn from 24 case study housing projects, including 12 reinforced concrete and 12 suspended timber floor projects. The data presented in the paper compares cumulative energy demand, GHG and the constituent parts of competing construction methods. The findings indicate that the timber floors use/create significantly less cumulative energy demand and GHG emissions than concrete floors—approximately 2.1 to 2.7 times less energy and 2.3 to 2.9 times less GHG. These findings are limited to the site slope and foundation soil types identified in the paper. The main application of the work is in guidance concerning the lowest environmental impact options for detached housing construction.

Q-Bot-A Robotic Solution for Insulation of Homes [Industrial Activities

Reports on the special features and applications supported by Q-Bot, a robotics company that improves the energy efficiency of existing homes by providing underfloor insulation to houses with suspended timber floors, of which there are over 8 million in England alone. Previously, the only way to insulate the floors of these homes was to take up the floorboards, a prohibitively expensive solution causing significant disruption and often forcing the resident to move out.

Reducing Ingress of Organic Vapours into Homes Situated on Contaminated Land

The efficacy of current landfill gas and radon mitigation measures for the prevention of ingress of organic vapours was investigated by the study of four houses situated on contaminated land in North West England. The chemical present in the ground of greatest concern for health due to exposure to vapour in the indoor air was hexachlorobutadiene (HCBD) and the concentration of this compound was used to assess the effectiveness of the remedial measures. A two stage remediation was undertaken. For a house with a solid floor the top surface of the floor was sealed and then for the second stage a fan was used to pressurise the soil gas beneath the house. In a house with a suspended timber floor, extra air bricks were installed to increase ventilation of the floor void and then a fan to further increase air exchange in the void. HCBD in air was monitored by both pumped and diffusive sampling methods. Control houses were also monitored that were not subject to remediation. It is concluded that the remedial measures used for radon protection of a suspended floor have the potential to reduce indoor HCBD concentrations by about 80%, at least in downstairs rooms (where initial levels were highest). The two techniques used for properties with solid floors do not appear to be as effective, and no benefit at all was seen without making allowances for changes in concentration that occurred in the control house over the same period. Further work is required to test the efficacy of the techniques over a longer period and under different circumstances of type of contamination and building characteristics.

Correlating and Predicting the Air Infiltration Through the Cracks of Suspended Timber Floors

This paper shows that the visible gap length may be used as a physical parameter when correlating pressure difference to volume flow rate (or air velocity) through the cracks between floorboards and can be termed the Equivalent Crack Length. The crack widths, which previously have been determined separately from the edge effect coefficient and the laminar flow coefficient, were significantly different. When analysed graphically they can be shown to correlate by an empirical relationship. A generalised equation is proposed that, in conjunction with the empirical relationship, allows predictions to be made of the volume flow rate through the cracks between floorboards for a known pressure difference.

Experimental Investigation of Air Flow Between Vertical Zones in a Dwelling

This paper presents the results of an investigation into the correlation between flow rate and pressure difference across a suspended timber floor. The power curve, the quadratic and linear relationships were used to fit the data. The Power Law and Quadratic Equation were used to fit the data and their effectiveness to describe the flow characteristics is confirmed. A closer examination of the crack parameters as defined by the coefficient of the quadratic equation has suggested that air flow through floorboards is likely to be dominated by the “edge effect”. At low pressure differences, the volume flow rate exhibits a linear relationship, but it does not pass through the origin. At high pressure differences (10–50 Pa), there is no evidence of the existence of a linear relationship. Consequently, the validity of the Linear Equation is not supported in this study.

Conformal mapping of a solution to a mixed boundary problem for soil gas flow

The principal soil gases of current concern to building are radon and landfill gas. The flow of these is generally considered to be dominated by viscous flow driven by pressure differences. This paper presents results for the pressure-driven flow of gas for problems relating to a building with a bare soil floor, for example below a suspended timber floor. This paper builds on a previous paper by mapping the solution to a mixed boundary problem onto another geometry. In a third paper these results will be compared with an analytical result from elsewhere and an experiment.

Solutions to a mixed boundary problem for soil gas flow

The principal soil gases of current concern to building are radon and landfill gas. The flow of these is generally thought to be dominated by viscous flow under a pressure gradient. This paper presents results for such pressure-driven flow of gas for problems relating to a building with a bare soil floor, for example below a suspended timber floor. The solutions address this problem in two dimensions as a mixed boundary problem. In the following papers this initial solution is then mapped conformally onto a more complex geometry, and the results are compared to another analytical result and an experiment.

Air infiltration through cracks in suspended timber floors

Although the power law equation may be used to correlate air flow rate to the pressure difference across a tongue-and-groove floor, the relationship between the coefficient and exponent and the physical parameters of the crack remains concealed to research. Moreover, the pressure loss through the cracks between floorboards of an in-situ floor is reasonably described by the empirical equation for cracks with known dimensions. This is Δ P = AQ + BQ2 for pressure differences of 0-50 pascals, although the recorded data is for 2-50 pascals. The present results lend support to the published expression for the determination of the theoretical edge effect constant B. However more work is needed in the area of laminar flow through very small, contorted cracks and in the assessment of the crack length. Finally, it is suggested that crackage between floorboards is due to the nature of materials and practices in the construction industry.

Heat losses from suspended timber floors

Heat losses through suspended timber floors and principal heat flow paths are identified. The performance of common insulates placed within and beneath the timber floors is measured in a test rig and the results reported. Special emphasis is placed on the ability to retrofit existing floors. A simple insulated radiative barrier placed under the joists is found to be as effective as 30 mm of insulation but is easier to install in existing dwellings. The reduction in heat loss using this method is 60–80%. A simple resistance model is used to predict heat loss accurately for low ventilation rates in the void below the floor. Les auteurs définissent les déperditions thermiques par les planchers suspendus en bois ainsi que les principaux cheminements des flux thermiques. On a mesure sur un montage d'essai les performances de différents systèmes d'isolation posés a l'intérieur et sous des planchers en bois. Les résultats obtenus ont été enregistrés. L'accent a été mis sur les possibilités d'amélioration de planchers existants par rattrapage. Il en ressort qu'un simple obstacle radiatif isolé posé sous les solives est aussi efficace qu'une isolation de 30 mm mais est plus facile à installer dans des logements existants. Cette méthode permet de réduire de 60 à 80% les déperditions thermiques. Une simple résistance sert à prévoir avec précision les déperditions thermiques. pour de faibles taux de renouvellement d'air dans le vide ménagé sous le plancher.

96/01987 Atmospheric chemistry of alternate fuels and reformulated gasoline components

Reducing heating costs is an important concern for householders, but many conventional methods of cutting down heating costs, such as insulating lofts and cavity walls and fitting double glazing, involve considerable capital outlay. An effective way of reducing heat losses with a minimum of capital outlay is to fit reflecting metal foil behind the central heating radiators, but little has been done to measure the amount of energy saved in this way. Similarly, a foil layer can be used to reduce heat losses from beneath suspended floors, but little data are available on its effectiveness. Work is reported here on experiments carried out in an environmental chamber to measure the effect on heat losses of metal foils behind radiators and beneath suspended floors. Reductions in the overall energy consumption of the room of up to 6% were recorded by installing foil behind a radiator, while the heat loss through the area of wall immediately behind the radiator fell to less than 30% of the original value. The heat loss from a suspended timber floor was reduced by up to 48% when foil was applied to its under surface.

96/01976 Weather data and heating-degreee days for Saudi Arabia

Reducing heating costs is an important concern for householders, but many conventional methods of cutting down heating costs, such as insulating lofts and cavity walls and fitting double glazing, involve considerable capital outlay. An effective way of reducing heat losses with a minimum of capital outlay is to fit reflecting metal foil behind the central heating radiators, but little has been done to measure the amount of energy saved in this way. Similarly, a foil layer can be used to reduce heat losses from beneath suspended floors, but little data are available on its effectiveness. Work is reported here on experiments carried out in an environmental chamber to measure the effect on heat losses of metal foils behind radiators and beneath suspended floors. Reductions in the overall energy consumption of the room of up to 6% were recorded by installing foil behind a radiator, while the heat loss through the area of wall immediately behind the radiator fell to less than 30% of the original value. The heat loss from a suspended timber floor was reduced by up to 48% when foil was applied to its under surface.

Moisture beneath suspended timber floors

Suspended timber floors are probably the most common form of construction for ground floors in existing British housing, although they exist in only a small proportion of newly built houses. If moisture builds up in the crawl space beneath the floor, wet or dry rot may begin, leading to structural damage to the floor and foul smells entering the living areas. The crawl space is ventilated by air bricks to prevent this happening, but this is often inadequate, and many houses suffer from damp conditions in the crawl space which are potentially harmful. These can be alleviated by increasing the ventilation, but the increased flow of cool outside air beneath the floor leads to higher heat losses in winter. Examines the relationship between crawl space ventilation rate and relative humidity.

Use of metallic foils as radiation barriers to reduce heat losses from buildings

Reducing heating costs is an important concern for householders, but many conventional methods of cutting down heating costs, such as insulating lofts and cavity walls and fitting double glazing, involve considerable capital outlay. An effective way of reducing heat losses with a minimum of capital outlay is to fit reflecting metal foil behind the central heating radiators, but little has been done to measure the amount of energy saved in this way. Similarly, a foil layer can be used to reduce heat losses from beneath suspended floors, but little data are available on its effectiveness. Work is reported here on experiments carried out in an environmental chamber to measure the effect on heat losses of metal foils behind radiators and beneath suspended floors. Reductions in the overall energy consumption of the room of up to 6% were recorded by installing foil behind a radiator, while the heat loss through the area of wall immediately behind the radiator fell to less than 30% of the original value. The heat loss from a suspended timber floor was reduced by up to 48% when foil was applied to its under surface.

Radon Remediation of Dwellings with Suspended Timber Floors - Case Studies from the Building Research Establishment (UK)

Abstract Dwellings with suspended floors and high radon levels are proving difficult to remediate. This paper reports on the experience of the Building Research Establishment in dealing with such dwellings. Brief details of the remediation of 14 houses are given, and comparisons are made between the effectiveness of the different techniques adopted. Natural ventilation, mechanical supply ventilation and mechanical extract ventilation are three techniques that have been used successfully as radon remedial measures. Preliminary results suggest that supply ventilation is more effective than extract ventilation.

Radon Remediation of Dwellings with Suspended Timber Floors - Case Studies from the Building Research Establishment (UK)

Radon Remediation of Dwellings with Suspended Timber Floors - Case Studies from the Building Research Establishment (UK)

Radon Reduction Techniques for Suspended Timber Floors and Pressure Field Extension Assessment of Hardcore Specifications

Abstract This paper comprises two case studies. The first describes a series of mitigation measures carried out in a small primary school fitted with a suspended timber floor. Radon levels had been successfully reduced but the floor subsequently collapsed due to an outbreak of dry-rot. The floor was replaced with a ground-bearing concrete slab fitted with a typical example of one of 200 or so sump-and-fan systems fitted by Cornwall County Council (CCC). Following consultation with the Building Research Establishment (BRE) a network of small bore pipes was fitted below the floor during construction to record variations in radon levels and pressures. The second case study describes the floor replacement at a second, similar school but with a permeable layer of material under the concrete slab and more pressure measurement points. The pressure measurements and their subsequent analysis are described and the performance of the two installations compared. Using BRE and CCC expertise, this technique is now being applied to a number of other replacement floors in order to assess pressure field extension in a variety of hardcore and blinding materials. It is hoped that by careful selection of hardcore and blinding specifications the increased pressure field extension obtained could result in new-build properties requiring fewer underfloor suction points and/or a reduction in fan power consumption with a greater degree of confidence of success than at present. The selection and design of suction systems to date has been on a very pragmatic basis.