Active Architecture Blog

'I’d like to convert my garage into a commercial kitchen. I’ve been baking from my current kitchen but it’s getting too small. Surely it’s just a matter of buying a few commercial benches, hiring a plumber, electrician and painting the walls right?'

Recently we completed the design and documentation for a conversion of a domestic garage into a commercial bakery kitchen. This was a huge learning curve for our client who had been working in her kitchen for 3 years, and saw the potential for her unused garage space to be better utilised, whilst freeing up her kitchen and dining for normal family living.
We asked her to deposit this question because it represents exactly the sort of learning you really want to do BEFORE you embark on these kinds of projects. 

So, the first thing to know is as soon as you propose a commercial activity in a domestic property, you need to not only comply with the standard town planning rules but a whole lot of other building code rules come into force that you wouldn't have to deal with otherwise. These include Fire, Accessibility, Noise, Ventilation, Surface finishes slip resistance/fire performance, more stringent plumbing and drainage requirements, amongst others. 

Our client had already obtained resource consent and spoken to the council's Health Team prior to looking for a designer which was definitely good management on her part. What she wasn't prepared for however was that due to the above compliance requirements, she was faced with the costs of the following:

• Replacing all the garage wall and ceiling linings with fire rated gib - the external walls required 120min of FRR which resulted in two layers of 19mm Fyreline!
• A whole new separate wall in front of the existing wall between the garage and adjacent bathroom because we had to achieve a minimum STC (Sound Transmission Class) rating between the proposed kitchen and the existing dwelling. To achieve this with the existing wall would have meant ripping out the shower adjacent in order to reline the wall from the bathroom side. 
• Insulation to meet current energy efficiency codes
• A connected hardwired smoke detector throughout the house and new kitchen.
• Replacing the existing doors between the garage and house with 60min Fire rated doors. 
• A greasetrap to the sewer and back flow preventor to the new fittings.

Another less known potential issue not necessarily specific to commercial activities (thankfully not required in this case) is found in the slab of existing garages. Especially prevalent in garages built pre 1980's, is the lack of DPM (damp proof membrane) under the slab. This is required by the building code to enable concrete slabs to be used in habitable areas, to stop moisture seeping up from the ground through the slab. So if you are eyeing up that garage that seldom houses a car and thinking that would make a great bedroom... be aware that you may well have to upgrade that slab to meet the code. Possible solutions include placing a polyethelene sheet over the top of the slab and either a new timber or concrete floor over. 

All More $$$$!

We hope this has provided some insight into the complexities of commercial activities in domestic situations. If you have questions of a similar vein and feel inspired drop them off at our Question Bank Page.