Due to current building regulations and the government pushing for more sustainable homes “Code 6”, construction related companies from timber frame suppliers to on-site manufactures are looking at modern methods of construction. Erecting closed panel timber frame systems can be an attractive option.
Timber Frame Systems
There are many timber frame systems available which offer a range of performance levels and they all have their pros and cons. Closed panel construction is a more effective build than standard timber frame methods but it has a higher requirement for accuracy and minimal tolerance in setting out. If you are experienced in timber frame construction then you will know the limits standard timber frames have with regard to site alterations, remedial and making areas fit/work. Some gentle persuasion is normally required however that mindset doesn’t work when it comes to closed panel timber frame houses.
Closed Panel System Construction
Designing closed panel systems becomes more technical and advanced in relation to connection details and introduces a variety of timber shapes, materials and steel ironmongery. Many of these connections and details will be hidden within the timber frame closed panel but they have an important role in the frame’s structural stability and tie in with the rest of the panels erected. It’s likely that the panels will come with an external membrane and internal airtight membrane already in place. This helps keep out the moisture during panel erection but the self-builder is well advised to get the building wind and water tight as soon as possible.
Before you start setting out panels a wall plate will be required. This material will be specified by the supplier along with fixing methods. This will be key to smooth panel erection so setting out all positions tying in with the structural design drawings is important.
When fixing the wall plates ensure you level all areas. This is because the closed panel systems will come square and require a level base which allows the panels to connect close together eliminating any gaps at panel joints.
During panel construction, look closely when setting out panels making sure you can clearly tell the top from the bottom side of the panel. Some will be more obvious than others but always make sure the panels are the right way up. This may sound condescending but some panels might have multiple studs located in areas designed to take high point loads from above. If the panel is upside down the panel may still fit but the structural integrity of the build could be affected in days if not years later.
Once the ground floor panels are in place, creating the first floor deck will be the next before this stage begins. Check to see if a mid floor membrane is required to wrap around the joist deck edge beam as this will help to make the build air tight by connecting the ground floor internal airtight membrane to the first floor around the joist deck. Before first floor panels are fitted, there should be another timber setting out locating plate. This will create the area for your panels to sit on. Once all first floor panels are in place and all fixings applied as per the supplier’s recommendations then the next stage will be the roof. These can be trusses, loose rafters or pre-made roof cassettes. Trusses and loose rafters have more flexibility and can be moved when required if needed, but this has to be approved by the supplier and this may affect the structural stability making the design certificate void.
Roof cassettes are really good for construction as you can create larger room areas and higher void ceilings (as they are insulated). Even though roof cassettes have many positives, they rely on the supporting panel to be as accurate as possible. If the walls are off plumb and not level this can affect all of your cassettes by preventing them from sitting correctly and tying in together. This can also have a significant effect on the build’s air tightness. In short, closed panel systems are a great build method but are less forgiving due to setting out errors and require 100% accuracy.
Closely study your supplier’s designs as there may be many types of ironmongery, connections and air tight materials required which will need to be placed during the erection. Missing their allocated position during the build may not be critical but can make it harder for you to achieve your final goal with the building’s efficiency.