Chris Burdett, Director of PipeSnug and building company Urban Spaces, takes us through a garden room build.
Garden rooms are becoming more popular, and even more so today as people work from home. They are an affordable build which in many cases do not need planning permission. I recently launched a company, Urban Spaces which specialises in designing and building garden rooms using SIPs (Structural Insulated Panels). Here I take you through the build from base to cladding.
Step 1. Foundations
There are a few different systems available including easy pads and a traditional concrete base. We use the UK Helix Screwpile system because it requires little or no excavation which not only speeds the build time up, it’s also more environmentally friendly as it requires no cement.
Step 2. Walls, floor and roof
The most popular types of wall and floor construction are still traditional timber stud wall and timber rafters but recently SIPs have gained traction and trust in the industry. SIPs construction has started to gain real momentum over the last 5 to 10 years mainly due to its speed of construction, superior air tightness and performance and lack of waste due to it being made off-site to the exact measurements. Care needs to be taken to fill any gaps with expanding foam to retain the heat performance. Installation is very quick, and you can generally have the floors and walls formed within 24 hrs. It’s important to add that you need to avoid getting the panels wet so we suggest an EPDM or single ply covering that can be laid over the roof instantly for weather protection and finished at a later date.
Step 3. Electrics
Always follow Wiring Regulations and stay safe. One downside to SIPs over traditional stud work is the 1st fix electrics can be awkward if you are not experienced. In the US, where they have using SIPs for generations, it’s quite popular to heat a ball bearing and drop it down the SIPs cassettes pre-install, creating neat cable runs and little disturbance to the air tightness. The other way and what I prefer is to batten out the whole frame with 2×1 batten. Because the SIPs are polyurethane sandwiched between OSB boards, this batten method provides easy cable runs with less planning and also means the electrical back boxes require just a small cut out of the OSB boards rather than deep incisions into the insulation.
Step 4. Windows, doors, and plasterboard
Consideration has to be taken into account for the height of the threshold when installing bifold or sliding doors. If the client has paid for the luxury of aluminium, they won’t appreciate having to jump over the threshold to get out! In most cases, we install a decked area as part of the build, and this provides the opportunity to install a low level or no sill threshold detail. If you are fitting without a sill, remember to install a DPC or aluminium tray and completely fill your perimeter of the frame with silicone to stop water ingress at a later date.
According to most SIPs manufacturers, foil backed plasterboard is not essential with SIPS as long as you are not in a high humidity environment. A vapour control layer is achieved externally with house wrap but foil back certainly won’t make the structure any worse either. If you’re building using stud work and rigid insulation, you must use foil backed and tape and seal the insulation. You also need to consider rigid roof insulation with firring pieces on top of a traditional joist roof, all of which adds to the final overall height, which may take you above the permitted development restrictions.
Step 5. Cladding
Once you have applied your house wrap to completely envelope your garden room, battens are applied to form an air gap and vapour control area prior to cladding. There are many options for cladding a garden room. Colour render systems can be applied on suitable render carrier boards, but most clients choose timber cladding. You get what you pay for on cladding, and woods like Cedar & Siberian Larch can last a lifetime if you provide a little care and maintenance and they are installed correctly. Shou Sugi Ban, or charred timber, is very in vogue with designers, and can last up to 100 years, but it’s messy to fit.
Once the cladding has been completed, the roof trims can be fitted, and the EPDM roof completed. We powder coat our own slim profile steel trims individually so we can colour match each design seamlessly. Gutter and downpipes need to be fitted and we always place these out of sight on the rear elevation, and into an accessible water butt if possible.
Internally, finishes vary but we recommend smart vinyl flooring which looks good, is very hard wearing and quick and easy to fit. Prior to fitting, we also fit tongue and groove chipboard flooring over a vapour layer. This levels out the floor and also decreases the door threshold height further, providing a really minimalist look. Skirting boards can now be fitted along with the second fix of all electrics followed by the decorating. Then, it’s decking if you want it!
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WATCH- how to build a Garden room with Chris from HiKOKI here- youtube.com/watch?v=bEPsHBcsOcQ