ALI DYMOCK

See Nick’s plans in high-res.

Ali: Hi Nick, thank you for joining this section of the website! We’ve shared quite a few emails back and forth over the course of your build and it’s been great seeing it come together. I’m going to get a bit more technical in this Q&A as there’s a lot in this build we can all learn from!

Starting with the plans, I can see you had everything designed from the beginning. Who did your plans and what were the full dimensions?

Nick: An old friend Sebastian Wolf, who worked with me for a year in my school art department before going on to become an architect, drew up the detailed plans. We started by chatting through our concept of what we wanted and didn’t want and after a few drafts he was able to draw out the detailed drawings. I had no idea how everything was going to come together, but once I had the drawings everything began to make sense. I had quite a few months to really study them as I was clearing the old garage and site and this was a huge benefit. One of his key inspirations was the tapering of the front face of the roof with the exposed joists. Architects like to show off the structure of their designs these days!

The old garage was less than 2m from the boundary wall and it was slightly out of line with how I wanted the new build to sit. By moving to just over 2m from the boundary to comply with permitted development it also meant that I would have room for a long lean-to woodshed.  The woodshed is not actually attached to the new build and as it’s under 2m high is allowable to be closer to the boundary. The total internal floor area of the build is just under 30sqm, also to comply with permitted development.

Ali: The tapered joists definitely gives a unique look to your garden room. Clearly having everything thought out prior to starting was a big help.

So, there was already a sound concrete base from the original garage, how did you go about expanding this?

Nick: The old base was several inches lower than where I wanted the build to sit relative to the surrounding ground so we excavated the additional areas to a good depth and put in a base layer of compacted hardcore. Next, steel mesh was positioned over the whole area and the new slab poured. I think there was about six inches depth over the existing slab.  At the same time the area at the rear had a thinner concrete base at a lower level for the lean to wood shed that finished short of the boundary where I had prepared a french drain.

Ali: Your roof slopes quite significantly. I presume you had to cut ‘birds mouths’ out of your roof joists – if possible, can you put into words how that was done accurately?

Nick: The roof pitch is 6 degrees, but looks more from the front due to the tapers on the overhang. All the roof joists were prepared some weeks before commencing building, including painting the exposed areas. The tapers were all cut with a Dewalt battery powered circular saw (an amazing tool used so much on the build and less than £100 excl. batteries). The birds mouths were marked up with a gauge and sawn by hand. Each end of the 4.8m rafters were cut on a mitre saw set at 6 degrees, and I used one of the off-cuts for the angle gauge. The 10″ Dewalt Mitre saw on a cheap Evolution stand from Screwfix is also a brilliant tool. I had a happy week cutting most of the framing timbers and labelling them all to make a kit of parts before starting.

Ali: Nice! So how on earth did you roll your rubber roof so nicely, it makes my efforts look completely haphazard!?

Nick: I had three days help at the start of building the frame from my brother and before he left to return to his home in Australia we placed a couple of OSB sheets up on the joists and somehow heaved 86kg of rolled rubber up two ridiculously sloping ladders. Could never have achieved that on my own.  I was blessed with beautiful autumn weather for the roof covering so the rubber was pretty pliable.  By using a long timber baton it was fairly easy to roll half of the rubber into a ‘carpet roll’ to the middle of the roof. Once that side had been adhered and swept smooth with a wide heavy broom (essential!) it was simply a matter of repeating on the other half. Oh, and I had watched your video of his roofing over and over until I could memorise the whole sequence.  Also used the discount code for significant saving.  Thanks Ali!

Ali: Ah that’s rather smart, I wish I’d thought of using a timber batten to roll it up!

I can see the mesh vents for ventilation of the cold roof. Tell us how that works.

Nick: Well I was a bit paranoid about vermin getting into the cold roof void so between all the joists front and back I stapled a fine galvanised wire mesh which is not visible. All the cladding has insect mesh between the boards and at the foot of the walls. The individual soffit boards below the overhang were also fitted with insect mesh. Working inside fitting all the roof insulation it was interesting feeling the significant draft in the roof void wherever I had left a small gap. These were filled but it was clear how good the ventilation was. Where I used galvanised cladding for the wood shed area, I used strips of plastic bird combs from Screwfix which filled the top gap nicely but still allows good airflow.

Ali: Thanks Nick, I think that will be really useful info to the cold roofers out there!

There is often a hard choice for self builders between an easier concrete base and a more insulated timber floor. You can of course put the insulation under the concrete or screed but you’ve put yours on top which seems rather obvious now. Can you tell us more and give, in order, the layers from bottom (concrete) to top (oak T&G)?

Nick: The original slab from the Banbury garage had always been dry so I assumed a DPM was beneath it. However with the extension of the base it seemed easiest to just add a new DPM on top of the completed new slab and tuck it up the sides of the frame footers. I had bought a big roll of DPM and by the time I had completed all the building work the DPM had plenty of small nicks in it, so I simply laid another layer on top before commencing the floor sequence. This was 40mm of Rigid PIR board, 18mm staggered T&G waterproof chipboard and then the engineered flooring with an expansion gap at the sides.

Ali: Brilliant. I think my next garden room will use the same method with perhaps a vapour barrier (basically another DPM) above the insulation or chipboard.

I can see this was a high quality build throughout, can you tell us the overall cost and how it compared with the expected cost/budget and also any particular suppliers you were impressed with?

Nick: When we started I had a figure of around £30k in mind including all the ground work, which I had a builder complete for me. That cost £4,250 as there was a lot of peripheral excavating. and four large skips loads of waste material to dispose of. The electrical supply from our house cost £1,500 to install and have signed off. The Slide and Fold windows from Sunseeker Windows were £6,500 and the two Schuco doors and window came in at just over £4,000 so a big part of the budget. I sourced these from a company in Poland found on eBay. Made to my dimensions (I wanted an extra wide outward opening door for the workshop with hidden hinges) and delivered for just £200, they were about 35% cheaper than could be obtained in the UK.  The quality is amazing though and they will last forever with no maintenance needed.

So overall, the final cost has come to just a few thousand over budget including the lean-to woodshed.  We love the Sunseeker doors/windows as they are so flexible and have such minimal sight lines, however the company have poor communications/customer service.

The beautiful Western Red Cedar came from Norclad LTD Bristol and was a case of you get what you pay for. Fixings, framing timber from my local builders merchants Bradford, where I worked hard to get good trade prices and there were lots of trips to Screwfix for bits and bobs.  Steel guttering is from Lindab and a lovely product. I have added a leaf trap and a diverter which can be used to fill a large dipping tank for the garden. We had bought a woodburner to fit in the main room, but with so much insulation the 1000w WIFI controlled electric wall heater (Tessy) barely ticks over to keep it super warm.  The flue work would have cost the best part of a grand and it would also have limited the way we can move things around in the space.

Ali: That’s great stuff, I’ll be giving Norclad a call in future and see if they deliver to my area.

Would you do anything differently?

Nick: So far I can’t think of anything I would do differently. I have loved every part of the build barring fitting the ceiling PIR insulation (horrible dust in the eyes).

Ali: Agreed! That’s the beauty of the warm roof method but fitting PIR into the walls gave me quite a few -dust in the eye- moments!

What would your advice to others self-builders be?

Nick: Really think hard about how you want to use the building. The architects drawings were key for me. It helped me to spend some months visualising each stage of the build before starting. Chances are many self builders won’t be doing this kind of thing too often so make the most of your build and try to achieve the highest standard you can.

Ali: What bits did you hire tradesmen for, if any?

Nick: I had a local builder and his son do the ground clearance with his mini digger and dump truck.  He also set out and laid the foundation slab. My brother from Australia gave me three days to set out the initial four frames and the roof trusses. He is an experienced timber framer so his help was invaluable to ensure everything was square. There was no way I would have attempted the plastering and a paragliding mate of mine did this beautifully with his brother (£700 cash/bargain).

Another friend talked me through the wiring and helped me install the consumer unit.  There is over 200m of cabling excluding the armoured cable link from the house.  A hard wired network connection to our home router. An external EV ready charging pod, RGBW LED lighting below the slide and fold doors, electric panel heaters, soffit downlights and the main room lighting are all app controlled and cables ready for quite a bit of garden lighting for when the landscaping is completed.  I do have an electrician coming to sign this all off.

Ali: So how long did it take you?

Nick: Once the groundwork had been prepared and the slab laid down it was 6 1/2 months to completion.  I had a break of 3 weeks over Christmas and New Year whilst waiting for the plasterers.  I work five days a week but only a couple of hours each day locally as a running coach, so I had plenty of time to dedicate to the build.

Ali: Ah the joys of retirement! That’s super Nick, thanks again for sharing your build with everyone, it’s a stunner. Enjoy it!