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Timber Frame Building Regulations are often mentioned together in discussions on design, planning and timber frame construction. While the two are often confused or lumped together as one, they are actually very different elements of the construction process. Planning permission is mainly concerned with the way urban areas develop and the impact new buildings will have on their surroundings. This can be due to their physical appearance, the size and height of the structure and any environmental arising from construction and future use. As we have discussed planning permission in previous blogs, we will refrain from further discussion here and focus on Building Regulations.
Building Regulations are instead a set of safety standards that apply to the construction of all buildings in the UK. By regulating methods and materials used in construction, they ensure that new buildings or improvements to existing structures are safe to use. This ensures that for the life of the building, all occupants living and working within or even visiting temporarily are as safe as possible. Any pedestrians or visitors passing through the immediate surroundings will also be protected if buildings are structurally sound and resistant to damage. People with disabilities must be able to easily access and move around within the building.
In the past, this could only be done by submitting detailed drawings ahead of the build to a Local Authority Building Control Officer to be signed off. Once approval was granted, site inspections would then be conducted at critical stages, starting with laying of foundations. If they were satisfied that Building Regulations were being adhered to, a certificate of compliance would be issued. For larger projects this is still the norm, but private approved Building Control inspectors can also sign off the work. Minor construction projects can also be signed off by the contractor working on the project if registered with a Competent Person Scheme. They will have been assessed to ensure their familiarity with Building Regulations and their competency to inspect their own work accordingly. While this can save time and trouble, always make sure the contractor involved is registered on the Government approved Competent Person Register before work begins. Complying with Building Regulations for timber frame construction is ultimately the legal responsibility of the property owner.
The following list addresses many of the main timber frame construction details governed by Building Regulations but is by no means exhaustive. If in doubt, consult your local authority or contractor for clarification to avoid any costly or dangerous mistakes or omissions. It should also be noted that building Regulations vary between England and Scotland and what is right for one may not be for the other.
Arguably the most important element of any construction project if the foundations are unsafe so is everything above them. Not all soil types have the same weight bearing capacity and different foundations may be needed from one site to another. The size of the building should also be taken into consideration, not just the footprint but additional stories that add weight. While pad foundations can support a simple arch or gazebo, for a whole building strip foundations (at least) will be necessary. For softer or loose soils, a raft foundation of reinforced concrete slabs or even piled foundations are a must. Failing to comply at this stage could halt the entire build before it starts.
For most types of timber frames, the structural timber must be strength graded to ensure it can support the weight of the building. It may be necessary to incorporate steel or structural timber composites to improve this for lower strength classes. Thankfully, oak framed structures are exempt from this as their natural strength and high load bearing capacities make it unnecessary. BS EN 336 stipulates minimum target sizes for structural softwoods, but again this does not apply to oak frames. Oak is also not subject to most rules for the moisture content of framing timber, but shrinkage must be factored into the building design. By purchasing oak frames from a reputable timber merchant, this will have already been taken into account during design and manufacture.
The durability of the timber used will dictate whether any pesticidal or weatherproofing chemicals must be applied. Where used, these must be safe for human and animal contact and pose no risk of pollution to the local water table. In some areas of England, Building Regulations require any softwood timbers to be treated against attack by the House Longhorn Beetle. The natural water and pest resistance of oak avoids these problems where used, but any softwood elements must be treated to avoid compromising the structure as a whole.
As noted above, any softwoods used in roof construction may require preservative treatment, but oak trusses will not. They should be designed and manufactured to conform to BS 5268-3. Even if solely oak trusses are used, at least some other components of the roof structure will be made of other timber and may need treatment. The method of joining them to the trusses, for example pegs or steel plates, may have to be altered to comply with Building Regulations.
When insulated properly, timber framed walls perform better than masonry walls of the same or comparable thickness. When combined with mineral wool insulation, the thermal efficiency of oak is further enhanced. This also provides the half hour fire resistance required by Building Regulations for domestic external walls. As oak has a slow, predictable burn rate, it easily meets the standards for fire prevention and control. If Timber cladding or sheathing is also used, a high level of sound insulation will be achieved. BS 5250 can be used to calculate the risk of interstitial condensation (the likelihood of water build up within wall cavities). A suitable Vapour control layer should be incorporated into the wall design based on this information.
Hardwoods Group offer a wide range of pre-designed oak frames suitable for extensions, garages, oak framed porches and more. These can be supplied as ready to build kits for ease of construction with the minimum of fuss. We also offer a bespoke design service for individual designs machined to your exact specifications. For further information, contact us, we will be happy to help.
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Foundations for Timber Frame Construction