Our friends Lindsay and David of L&D Construction have been first-movers in the ADU construction residential market in Denver. Having built their own ADU above their garage in the West Colfax neighborhood and experiencing the benefits of short-term rental income; they have become strong advocates for this growing market. Now 80% of their construction projects are ADU’s and they are projecting they will build 12+ ADU’s this year and 20 in 2019.
Although our Tandem House is not an ADU, the Tandem House building type provides many of the same benefits as an ADU (and more, see Tandem House vs. Accessory Dwelling Unit) and should be considered when debating the cost/benefits of building a detached unit on a residential lot zoned for ADU or Tandem House in Denver.
In only 10-days our two story house has risen out of the ground for the biggest impact yet. It was a fun process to watch the SIP (Structural Insulated Panel) crew unconventionally construct the Tandem House using these pre-manufactured walls (and roof). The walls, with their insulated core that is sandwiched between two layers of structural board already have windows, doors and account for cutouts for details like structural beam fittings. The use of these panels require more design drawings and a higher level of detail upfront but when they arrive onsite, installation is a quicker process than traditional stick build construction. The house is framed, sheathed and insulated at the same time. The overriding benefit is a tight building envelope with higher insulating properties.
Now to the fun part… the timelapse!
Framing out the Garage
Joists above the Mudroom
Steel Structural Beam
Setting the Steel Beam
Steel Beam Detail
Joists above the Living Room
Looking in from the Wall of Windows
Enjoying the Sunshine on the First Floor
Sheathing the Second Floor
Ceiling Height Change. Kitchen has a higher cieling
We have moved past the earthwork phase and the site is feeling a little more clean. Plumbing, rock aggregate base and floor insulation went in before the concrete floors were poured.
Scott has been doing a lot of the work to prepare for the installation of the SIP panels. The sill plates will form the threshold for the insulated wall panels (SIPS) to attach. Over the holiday week the first floor joists went in along with the structural wall that support the joists at the future basement steps (thanks to my brother Kareem for all the help!). The floor sheathing is nearly complete and we’re ready for the walls to arrive!
We have a basement! It’s exciting to finally see walls up. Within a week the forms were built along with the rebar grid and once the inspection was approved, concrete was trucked in and pumped over the house and into the basement forms in the back.
More process photos. Almost ready to start backfilling the site.
Concrete pump truck
Forms stripped once concrete set for a week
Waterproofing was sprayed on
Insulation is the last step before we can start backfilling
Trenches were dug to make way for the basement perimeter drain pipe that leads to the sump pump that will prevent ground water flooding
Excavation has been a long process because of Denver’s abnormally wet fall weather and the limiting size of our lot. All the rain and an early October snowfall left the soils saturated which you can imagine is less than ideal for a skid steer bobcat. Its difficult to move heavy dirt around and even more difficult to navigate up a steep ramp on muddy ground. Hence the delay between weather events as we waited for the site to dry out.
Another limiting factor has been the amount of cut dirt that we have had to truck away (15 truck loads). Also, because our site is so constrained there is little room to store dirt that we will later backfill when the basement walls are formed. Luckily we have great neighbors that let us store a pile in their yard for a couple weeks.
Check out time lapse video showing the remaining excavation work and the laying out of footing forms for the basement and future garage and mud room on the first floor.
Excavation is well underway. After 5 long days of work there has been a lot of progress! The hole is nearly 10 feet deep but doesn’t quite cover the extent of the basement. We’re probably 2/3rds of the way there.
Although we are not done excavating, because the caissons are now exposed, we were able to get the City to inspect and close out the shoring permit and while they were at it they closed out demolition. Both were approved which meant on Friday we got our official building permit! 7-months to the day from when we made our first submission to the City.
Up next is finishing site excavation and prepping for foundation footings. Once the footings are poured the formwork can be built so that the concrete walls for the basement can be poured.
Last week we finally heard back from the City that our construction drawings were approved. So we didn’t waste anytime! Within the week we completed our initial City site inspection and subsequently were given our shoring permit. And, today we officially broke ground. The contractor dug and poured 13, 20-foot deep caissons that abut the property line to the north.
Shoring was required before excavation because the short 5-foot distance from the neighbor’s property line and our new basement does not leave room for gradual grading that could prevent the earth from sliding into the hole that is dug. So alternatively, the closely spaced caissons hold the dirt back and prevent any site disturbance to the neighbors property. The caissons will need to set for 7 days before site excavation can begin.
You may have noticed that our garage demo has been more intentional than the typical demo process. Our goal has been to minimize the amount of waste that goes into a landfill and to instead find creative ways to re-use material. Demo Pt. 1 and 2 videos show that we saved the wall bricks and roof trusses that are now stacked neatly in our backyard. We will re-use the brick on the new 1-car detached garage. To complete the garage demolition, we broke-up the concrete foundation and filled wire mesh gabion baskets. The seat height walls will create an entry sequence from the street and will line the walkway back to our new house. See the photo gallery below to check out our process and final product.
To complete the look, we will eventually plant tall native grasses behind and in between the walls, add a wood bench to two of the walls and the last vertical wall will become an address sign.
If you have been following the Blog you know that we submitted our permit set to the City back in February (see 2.14.17). So why do we only have a demo permit and why is it taking so long to break ground? Trust me, we get restless too and wish we were 10 steps ahead of where we are. But, we realize that this is a process that we are not rushing and thoroughly proceeding through to ensure it gets done right.
So what’s been happening between garage demolition and the eventual breaking ground? We still need a building permit! The permit is pending City approval because they need to see shop drawings from our Structurally Insulated Panel (SIP) manufacturer. Which we waited to proceed with until we were positive of the City’s impending approval of the project.
As mentioned previously (see Energy Efficient Home) we will be using SIPs for our home construction because they are more energy efficient, stronger, quieter and more airtight than older technologies. The SIPs are a major piece of the project and will make up the structure (… or bones) of the home; the walls and the roof. Therefore, in order to approve the building, the City needs to see engineer-approved plans and details that show panel elevations and thresholds between the foundation and walls, and the walls at ceiling and floor transitions. These drawings get very technical and have required a lot of attention and coordination between Scott and the manufacturer over the past few weeks.
In addition to the structural importance of the SIPs, when delivered to the job site, the pre-fabricated panels will have the windows, doors and electrical fittings cut out. This opened up a whole other level of detail that Scott needed to refine and work into the drawings. And, in order to determine a final layout, we were forced to determine final window sizes and location, which is dictated, by the window manufacturer and budget. Through this process, we have chosen Alpen Windows based out of Niwot, Colorado. Similar to Zola Windows, who we were considering previously (see Steamboat Field Trip), Alpen Windows are European style and triple pane. Alpen was set apart not only because the windows fit our budget but also because they are manufactured locally and at altitude. There was a concern for Zola Windows because they were manufactured in Europe and would be shipped to high altitude. With Alpen, we can eliminate the concern for window shattering due to atmospheric pressure changes.
Case and point, we have been busy, to say the least! Each step is getting us closer to breaking ground. Currently, the SIP shop drawings are back in the hands of the manufacturer and under engineering review. There will most likely be another round of back and forth but we are anxious to get the drawings back to the City so that we can get our building permit!