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Commissioned Reports - Construction


Date: 2006
Title: FC Wales - Affordable Housing sustainability and construction quality criteria (231187)
Authors:
Full Report: Awaiting electronic version


Date: 2006
Title: Greenhouse Gas Emissions Comparison - Carbon benefits of Timber in Construction.
Authors: Report produced by Forestry Commission Scotland
Full Report: PDF

Summary
This assessment compares the greenhouse gas (GHG) emissions arising from the embodied energy of a variety of different building materials that could be used in the construction of a 2 bed semi-detached house, a 3 bed detached house and a 4 storey block of flats. In addition this study quantifies the potential GHG benefits of increasing the timber content of the 3 types of accommodation.

The impact of transport on the overall GHG balance of timber is also assessed by comparing a range of hypothetical supply chains.


Date: 2005
Title: Capturing the benefits of timber frame
Authors: Report commissioned from BRE
Full Report: BRE Digest 496 available from www.brebookshop.co.uk

Summary
Resulted in publication of BRE Digest 496 Timber frame – a guide to the construction process. Follows the procurement and construction process, then describes the various elements of a timber frame and the main types of TF construction (platform frame, floor-to-floor panel frame, vertical panel frame, volumetric). Three case studies describe the benefits experienced from using timber frame compared with traditional methods.


Date: 2004
Title: Home Grown softwoods for UK timber frame construction (215340)
Authors: Report commissioned from BRE
Full Report: PDF
Interim Report: PDF

Summary
The project involves a critical, independent evaluation of home grown softwood for the UK timber frame construction sector. This involves selection and assessment by comparison of sample batches of home grown and imported material, together with panel production trials and conditioning tests on panel assemblies.

Main Findings:
Low levels of distortion were found present in both imported and home grown timber as supplied, although the home grown timber showed a greater tendency to distort in bow and spring when allowed to dry unrestrained. This was due to the level of compression wood within the sample batch. Levels of twist observed were 20% higher on average in the UK timber following unrestrained conditioning compared with imported timber.
   
The home grown timber showed better performance in compression tests due to the greater frequency of knots. The greater frequency and size of the knots in the home grown timber is more likely to cause a problem with nail fouling. However during production trails at Stewart Milne Timber Systems no instances of nail fouling were observed, although the number of panels made was limited. In another BRE Project (DTi sponsored Pii on “Providing High Quality Timber for the UK Construction Sector”) a scanner based solution for knot fouling problems has been developed.

It was observed that the nails fixing the sheathing OSB had been over-driven on the panels manufactured in the trials and that for this reason racking resistance values were below the normal level expected. This is an important consideration for timber frame manufacturers. The level of pressure for nailing can be reduced.

During conditioning tests on panels fabricated by BRE from supplied moisture content to levels below that anticipated in service, no significant distortion was observed. This tends to confirm that timber frame construction provides a high level of restraint for timber undergoing a change in moisture content.

Stewart Milne Timber Systems Ltd were not willing to fabricate panels made from UK timber for inclusion into any full scale structure. The company currently obtain imported timber at a discount and for sizes other than 89mm x 38mm CLS, such as 140mm stud sizes and also joists.
On the basis of the above work, it can be concluded that UK grown timber is well-suited to timber frame panel manufacture, although economic factors and company policy may count against its uptake. Close regard should be given to improving quality control in the UK sawmilling sector. This could be achieved through the application of timber scanning technology.


Date: 2001
Title: Spruce Joinery Review (204202)
Authors: Report commissioned from BRE
Full Report: Awaiting electronic version

Summary
This project is a feasibility study on the use of Scottish grown Sitka spruce for joinery. The study was jointly funded by Scottish Enterprise.

The aim of the work was to evaluate the potential of using Scottish grown Sitka spruce for joinery. Scotland has the world's largest resource of Sitka spruce and the volume of timber available is increasing each year. Commodity timber products such as pallets and packaging are coming under increased price competition from imports. In order to maximise the value of this Scottish grown spruce it is essential for producers to find new value added markets. Joinery offers a substantial market for timber, both in the UK and Europe. Due to a number of technical issues, Scottish grown spruce has not previously been used for joinery. However, re-engineering using green gluing could now make it possible to access this market.

This report presents technical and marketing issues that must be resolved in order for Scottish grown Sitka spruce to access the joinery market.

Key Tasks:
1. To evaluate the potential size of the market for Scottish joinery products
2. To establish the technical requirements, including standards, for joinery products and, through
    field research, to determine how well Scottish grown Sitka spruce meets these requirements
3. To establish the processing and technology requirements for manufacturing Scottish grown timber
    joinery products
4. To review the coating types and their suitability to optimise the performance of Scottish grown
    Sitka spruce 
5. To consider the logistics and methods of delivery of Scottish grown timber joineryproducts
6. To evaluate the best approach to penetrating the market with Scottish grown joinery products
7. To determine the optimum routes and costs for prototype and full scale development.

Key Outcomes:
1. Analysis of market data from a range of sources has shown that there is a considerable market for joinery that could potentially be accessed by Scottish grown spruce. In addition to the UK market, there could also be export opportunities if the right product was created. It was also noted that the higher value added markets such as joinery are less susceptible to price competition than commodity markets such as pallets and packaging.

2. The technical requirements with regard to standardisation for joinery timber are discussed as they stand. It is also explained that a new provisional standard, prEN13307, has been drafted and it will be essential to follow and influence the development of this document.
    There are two options for the use of Scottish spruce in joinery. These are the use of battens or falling boards. There are advantages and disadvantages for both. It is probable that battens would only be suitable for joinery if the customer (joinery producer) can accept standard construction dimensions of timber, but this is feasible. Otherwise falling boards appear better suited for joinery. With falling boards the durability will be more important due to the increased presence of sapwood. This will need to be addressed.
    The technical issues relating to growth rate sorting, compression wood and surface finish have been discussed but need to be researched to establish their importance for both finger jointed solid wood and laminated wood.
    The Field research was essential to carry out detailed mapping of the occurrence of knots and defects in both falling boards and battens. This allowed different defect cutting scenarios to be evaluated. In the future this will enable informed decisions to be made regarding which joinery grades provide the greatest return on investment. In total three batches of timber were assessed. These comprised two packs of falling boards of two different widths from one sawmill and one pack of battens from a second sawmill. A total of 277 falling boards and 48 battens were assessed for growth rate. Those that passed the growth rate requirements for external or internal joinery were mapped in detail. In total nearly 4,000 knots and 4,000 clear sections of timber were measured and recorded, which resulted in the recording and entering of over 15,000 data points. The results from modelling of the data showed good potential for the material to be re-engineered for use in joinery.

3. The processing and technology required for manufacturing Scottish grown timber joinery products are described. There are a wide range of machines available for each operation: scanning, cross cutting, finger jointing, planing and laminating. The exact machines for an individual sawmill will depend upon the budget available and the throughput required. The information provided will give Scottish sawmills a good understanding of many of the technical issues to be considered. The use of a scanner to identify and mark defects will be essential for commercial defect cutting and finger jointing for joinery. The scanner could supply two high speed through-feed cross cut saws, although a single saw would be appropriate initially. This would feed a packet type finger jointing machine, followed by a moulder for surfacing prior to laminating.

4. A review is presented outlining the work that has been carried out relating to the performance of painted spruce. However, the research was predominantly carried out on slower grown Norway spruce, so some further testing will be essential to establish the performance of Scottish Sitka spruce.

5. It is clear that there is real potential to use Scottish grown spruce for joinery but this will be dependant upon further research and development. However, the establishment of strategic partnerships within the development work will assist the future market success of the products and reduce the time to market.

6. The same is true for the creation of a market for Scottish spruce joinery. If the products are developed in co-operation with joinery manufacturers and house builders then long-term partnerships and markets can be created as a result of the essential development work that is required. This can also be applied at a European level in order to gain access to the Dutch and German joinery markets where spruce (whitewood) could be more readily accepted. In the UK, the negative perception of spruce for joinery and the outdated attitude to the use of finger jointing need to be overcome.

7. Strategic partnering will be essential in order to bring joinery products to the market place and these partnerships can be initiated through the development work that is needed. A number of technical issues require further work to enable Scottish spruce to access the UK joinery market. These issues are summarised in Chapter 8 and include: green gluing for joinery, growth rate sorting, detection of compression wood, defect scanning, approval of polyurethane for joinery, screw holding, surface hardness, coatings, wood modification, technical performance and cost analysis.


Date: 2000
Title: Students Hall Project – Aberystwyth (81-433)
Authors: Report commissioned from BRE
Full Report: PDF

Summary
This project produced an Information Paper 19/00 Five-storey timber frame hall of residence - a reconstruction case study. This describing the design and construction challenges for a replacement student hall of residence on the esplanade of Aberystwyth. The case study focuses on key features of the project with special attention given to the 5-storey timber frame structure. The building was required to re-house over 100 students displaced by fire damage and had to be designed and built in the shortest practicable time for economic reasons. It also had to meet demanding architectural, technical and conservation requirements.