Tuesday, April 19, 2022

INTRODUCTION MODERN TIMBER-FRAME CONSTRUCTION

Modern timber-frame construction in the UK has been developed from North American and Scandinavian methods and bears little resemblance to the traditional, heavy oak-framed buildings of the late Middle Ages. Indeed, most modern timber-frame houses, when built, are visually indistinguishable from their brick and block counterparts. Modern timber-frame construction is based on off-site prefabrication and typically has the roof, the internal and external walls, the first floor and, often, the ground floor built in a factory and then transported to site for assembly.


Introduction Modern timber-frame construction


Although it is not difficult to find examples of ‘modern’ timber framing from the first part of the twentieth century, it did not become a popular form of construction until the 1960s. By the beginning of the 1980s, some 20 per cent of new houses were timber framed, but adverse publicity about quality and construction methods reduced this percentage considerably during the middle of the decade. Since the 1990s, improved design and more rigorous quality control have helped to reinstate the image, and the popularity, of timber-frame housing. The trend by successive governments to encourage the construction industry to adopt prefabrication techniques, such as modern methods of construction (MMC) – see Chapter 1 – as a means of improving quality and avoiding the problems of skills shortages has also given a boost to timber- frame construction. For the past few years, the share of timber-frame construction in the UK housing market has been about 25 per cent.

Timber-frame construction offers several potential advantages for developers over traditional brick and block forms of building. These include:

  • faster construction (producing a quick return on borrowed capital and less financial risk) – on-site construction is reduced because of the prefabrication that takes place in the factory. There is also a time advantage because a relatively weathertight building can be formed in a few days and this allows internal work to start quickly. In addition, there is no time lost waiting for the mortar to dry out (as would be the case with masonry) and freezing conditions will not affect site erection (unless an external masonry skin is added)
  • less dependence on traditional ‘wet’ skills, such as bricklaying and plastering
  • less costly due to the greater use of unskilled site labour
  • reduced dead-load resulting in lighter and cheaper foundations.

In addition, timber-frame construction can be relatively easily adapted to encompass high levels of thermal insulation.

Timber-frame construction offers the potential for greater quality control, in so far as this is potentially easier to achieve in factory conditions rather than on site. However, even where stringent factory quality control checks are in place, there may be installation deficiencies in relation to important details, such as vapour control layers, fire stops and cavity barriers, etc. and, therefore, good site management and control is essential. Prefabrication off-site also requires accurate setting out on site – if components do not fit properly, quality may be compromised.

Monday, November 1, 2021

Elements That Contribute Towards a More Energy Efficient Home

It has been estimated that buildings are responsible for 40% of global carbon emissions. Given the ongoing climate crisis, the need to address this has never been greater. One way of doing so is by making your property energy efficient – in the UK, 14% of emissions come from energy use in our homes, and in 2017, consumption actually increased. There are several ways to go about building an energy efficient home and the payoff is not only environmental but will save a lot of money on bills.


Energy efficiency is not just about using sustainable materials and building techniques but constructing your home in a way that cuts energy consumption in half over your over the property’s lifetime. Investment in good design, choosing the best fabric solutions, and installing an appropriately sized heating system are all crucial steps.

Elements That Contribute Towards a More Energy Efficient Home

Thermal bridging


Central to energy efficiency, a thermal bridge occurs where the insulation of an element is compromised. This happens at junctions, where walls meet floors or roofs, or around openings, doors and windows - and it’s not uncommon for a new build home to contain hundreds of defects.
A solution is to build parts of the home in a factory. With a diminishing number of skilled trades in the UK, modern methods of construction use off site solutions to control quality, improve tolerances and eliminate the energy performance gap. This type of innovation is often considered a risk, but sourcing and relying on traditional trades to deliver an energy efficient home is a risky option as well.

Airtightness


Airtightness is about eliminating unwanted ventilation in buildings, typically draughts around openings and junctions, and it is crucial to get it right at the outset. Houses are made up of lots of incompatible materials so there is a need to interface blocks, timber, insulation and concrete, as well as doors and windows, and that takes a high degree of skill, as these may expand and contract at different rates once the house is heated up.

Insulation


Insulation is critical to achieving Building Regulations, but also will determine the long-term running costs of the house. We advise looking for an optimal thickness level and ensuring that you have high quality installation, as any gaps will seriously affect performance.

Lightweight properties can be prone to overheating, in which case you should introduce thermal mass through a solid floor or solid internal walls to help manage temperature extremes. The thermal mass acts as a passive store, so on hot summer days the building keeps cooler, and in the winter the thermal mass keeps a minimum temperature that can then be topped up by a few degrees to achieve the comfort level required.

Solar thermal and PV panels


Once you’ve built an excellently insulated and airtight building, heat loss can be so small that a traditional heating system would be oversized. Once this need for heating is minimised, hot water becomes the primary demand, so using a cheap and established technology such as Solar Thermal panels can provide hot water across many months of the year, significantly reducing costs. PV panels are not currently subsided through a feed-in-tariff, but integrated PV roofs in various finishes are available to reduce the overall running costs and carbon emissions of the home.

People are increasingly having a say in how their property is built and it’s crucial that they appreciate lifecycle, while having an open mind about offsite construction. To help builders and customers identify what good looks like, BRE has developed the Home Quality Mark, which covers all aspect of a home, environmental social and financial. To provide confidence in buying an off-site fabricated home, BRE has also developed a product standard BPS 7014 to provide confidence in the off-site systems and products being introduced.

Monday, April 11, 2016

Control of Ground Water

This can take one of two forms which are usually referred to as temporary and permanent exclusion.



Permanent Exclusion: this can be defined as the insertion of an impermeable barrier to stop the flow of water within the ground.

Temporary Exclusion: this can be defined as the lowering of the water table and within the economic depth range of 1500 can be achieved by subsoil drainage methods, for deeper treatment a pump or pumps are usually involved
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Simple Sump Pumping: suitable for trench work and/or where small volumes of water are involved.

Problems of Water in the Subsoil

1. A high water table could cause flooding during wet periods.

2. Subsoil water can cause problems during excavation works by its natural tendency to flow into the voids created by the excavation activities.

3. It can cause an unacceptable humidity level around finished buildings and structures.

Underpinning Columns

Columns can be underpinned in the some manner as walls using traditional or jack pile methods after the columns have been relieved of their loadings. The beam loads can usually be transferred from the columns by means of dead shores and the actual load of the column can be transferred by means of a pair of beams acting against a collar attached to the base of the column shaft.

Underpinning Columns

Root Pile or Angle Piling

This is a much simpler alternative to traditional underpinning techniques, applying modern concrete drilling equipment to achieve cost benefits through time saving. The process is also considerably less disruptive, as large volumes of excavation are avoided. Where sound bearing strata can be located within a few metres of the surface, wall stability is achieved through lined reinforced concrete piles installed in pairs, at opposing angles. The existing floor, wall and foundation are predrilled with air flushed percussion auger, giving access for a steel lining to be driven through the low grade/clay subsoil until it impacts with firm strata. The lining is cut to terminate at the underside of the foundation and the void steel reinforced prior to concreting.

Root Pile or Angle Piling

In many situations it is impractical to apply angle piling to both sides of a wall. Subject to subsoil conditions being adequate, it may be acceptable to apply remedial treatment from one side only. The piles will need to be relatively close spaced.

Friday, December 11, 2015

'Pynford' Stool Method of Underpinning

This method can be used where the existing foundations are in a poor condition and it enables the wall to be underpinned in a continuous run without the need for needles or shoring. The reinforced concrete beam formed by this method may well be adequate to spread the load of the existing wall or it may be used in conjunction with other forms of underpinning such as traditional and jack pile.

'Pynford' Stool Method of Underpinning