There are 2 types of roofs being flat (1.5 degree) or pitched (traditional hip, gable, etc).
There are 2 ways to do a pitched roof with our system being:
Adding a traditional timber truss to top of our system then roofing as normal
A composite skin with Polyurethane Rigid Foam (PU) filled void which we haven't decided yet whether we will do this in the early stages as it still has some obstacles to overcome (mainly transport of larger structure).
For the purpose of this blog I will discuss only the flat type roof (lower section roof shown above) which is our preference due to speed, watertight and same methodology as rest of house.
According to our calculations, there is already ample strength in the ceiling system (structure already below), so a roof system added above needs to think more about form and water fall / water tight. So the initial direction for this is to build this roof using fibreglass in one piece like the reverse of a boat.
A traditional roof is made in many stages and takes around a week on a building site from first to last trade. They are also governed generally by straight angles (no complex roof falls unless you pay a huge premium for skilled workers who are not in a rush). Using composites we can ignore all these current obstacles.
So what is crazy exciting for us is the opportunity to build this roof a completely new way using some very old process they have been doing in boat building plus new technologies of PU and 5 Axis CNC machines. Essentially what we are needing to build is a 'reverse boat' where we need to keep water away from the house.
The reason we design using a 3D design program (Revit) is the outputs available to us are brilliant. So using the model (image earlier in this blog) which is modeled to be exactly what is being built on site, we can then remove all the un-needed materials to have just the roof section remaining:
From this model we can export it to a CAM software which will speak to a CNC machine. Now cut this 'shape' out to be exactly as it was
Whats exciting about this (apart from the obvious) is that we can do what ever shape we want. So as we were trialing the process using Revit a very new and unique way to drain a roof came about as a result of what would have been a flaw to this idea. This is an angled roof on a 45deg plain. Simply put this means each roof area drains to the corners - so in the model above, there would be 4 draining points (4 x down pipes) and a lot less joins and points where water could penetrate the house. Extremely simple; and really smart way to drain a roof which simply isnt done in traditional building methods.
Using a composite sandwich panel for the base (due to lifting we may need to add some structural members to this - review that later). Then add a 'blank' slab of PU rigid foam approx 300mm - 450mm high (what ever is required) then have the 5 Axis CNC machine cut this out. So the result will be a rigid, closed cell (meaning water tight) foam shape matching exactly what the CAD file required.
CNC machine that will cut out this shape.
Apply fibreglass to the entire shape using a 'chopper gun' the same way you do in boat building (meaning needs to be rolled and post-machined / trimmed).
A chopper gun cuts and 'spits' fibreglass roving as well as mixes and 'spits' resin at same time onto the shape. All that is required is rolling the 'bubbles' out to make the composite strong and water tight.
Apply an outer membrane which is smoother and more aesthetic (not required but likely will be part of the process).
From there is a matter of shipping and craning into place then sealing any joints.
This can all be done in 1 day. So ignore the impressive speed, the end product is very impressive in that it will never leak. Lets say there is a blockage in the down pipes, the water would build up in the roof system like a swimming pool before it leaked! Traditional houses would leak everywhere as they are designed only for water to fall down, not pool.
The cost to do this is way less than traditional roofing, so this is one of the elements we are relying on to counter the expensive cost of Carbon Fibre.