Geotechnical Engineering and the Foundation

Back when I signed a purchase and sale agreement for the land, I got a set of docs for the lot. This included a survey, a geotech report, and some proposed plans. One thing I noticed when reading over the geotech report was that the engineer recommended using pile foundations due to softer soil on my lot. The foundation drawn out in the permit set was a standard spread footing foundation. When I pointed this discrepancy out to the architects, they did recommend we talk to the geotech enginner and find out if this is an issue. Unfortunately, the original engineer who wrote the report was unreachable, so I had to hire a new one to do an analysis on the lot.

About two weeks later, the new geotech engineer and my structural engineer met and worked out that there should be a mat-slab foundation for the house. This means that instead of just having a perimeter of concrete holding up the full weight house, a slab of concrete will be poured over the entire footprint of the house to help distribute the weight. I was told the previous spread footing foundation would have most likely been sufficient, and wost case is I would have seen some very minor cracking over the years. The new foundation won't have this problem at all. That makes me feel better, especially for such an important part of the house. 

The improved foundation uses more concrete and is more expensive, so the cost of building the house went up, but not by much relatively speaking. There is an additional benefit, however, to having a foundation of this type. It creates a very large crawlspace under the garage with a finished concrete floor. This opens up the possibility of using this area as a mother-in-law unit at some point in the future. 

The revised plans will be submitted for post-permitting, and it won't hold up construction. The city is estimated to charge about $600 approve the revision to the permitted plans. 

Permitting

Once the plans for the structure and layout of the house were completed, the next step was to get it all ready for permitting. This is a rather tedious process involving describing every detail of the structure and surrounding areas. Pb Elemental spent October drawing out all the detailed plans.

During that time, a set of the plans were also submitted to a structural engineer. The structural engineer's job is to figure out what type of framing should go where and how it should be attached so that the house can stay upright and not fall apart or exhibit other unwanted behaviors.

One challenge the structural engineer had for this project was to figure out what was necessary to implement the cantilevered portion of the house. Before we submitted the project to engineering, we were debating whether or not there should be a post to support the cantilever. Once the engineer ran the numbers, he determined that it would require around $15-20K of structural steel to have a freestanding cantilever of that size! That result pretty much made the decision for us. Even with the post, there will be some steel I-beams in the house to support the structure, but much, much less of it.

As soon as the engineer and Pb were done with their work (around the end of October), a full-sized set of plans were submitted to the city (along with a ~$3k deposit from me), and then it was time to wait.

About a month and a half later (around mid December), the city came back with two minor corrections they wanted to the plans. The corrections were no big deal to make, so a week later we re-submitted. By mid-January (along with a second payment), we got issued permits from the city! Total elapsed time for permitting: about 2.5 months (including Christmas and New Years). Total cost to get permits: about $5K.

Final Draft / Virtual Tour

Around the October timeframe, Pb Elemental got the final draft of the house completed. One of the issues they realized with the new exterior is that the shell extended out about 8-10 feet beyond the setback of the lot! Oops! They ended up resolving that issue by shortening the height of the shell and using railings for the rooftop deck instead.

They got a fancy updated 3D model of the house too:

 

 

There were many subtle stylistic tweaks done to the house at this point. Here's what the final interior plan looks like (screenshots taken from the permit set.. ignore extra lines):

We start at the bottom floor. There's a media room and large storage/server closet. All of the high-tech wiring will be routed to that location. There's also a half-bath added by request. 

 

Going half a flight up, there's a sliding door to the ground-level patio.

 

 Going into the entry and up the stairs leads you into the living room. Of note here are the sliding doors from both the living room and bedroom. Opening both up, should create a large indoor/outdoor area. For parties, the bedroom can be blocked off with a pocket door. The guest bath is off on the side of the kitchen out of the way of the entertaining area. 

All the flooring throughout the house is concrete. This will especially help unify the surface on the deck with the surface indoors. That seamless effect will also be noticeable in the bathroom. The plan right now is to run the concrete surface straight into the shower and slightly slope the surface to allow for proper drainage. 

And lastly, following the outside stairs, you get to the rooftop deck. It overlooks the green roof over the master bedroom and kitchen. There is also a skylight positioned over the island. 

There are lots of windows throughout the house, and it does serve a practical purpose. They will bring in lots of natural light into the house. The cloudy season in Seattle is very long, and this should almost eliminate the need to use indoor lighting during the daytime. It also helps give a visual connection to the outside, thus furthering the indoor/outdoor theme. While my views will be very urban - no million dollar panoramas or water views - it will be better than staring at a blank wall.

Third Draft

About a month after showing me the second draft (end of September), they came up with what would be close to the final design of the house. The interior design remained mostly the same - some minor tweaks here and there. The exterior, however, got a major overhaul. They dropped the concept of two volumes, and instead came up with a sharply-angled exterior shell for the house. Very cool.

Materials

During one of our meetings, we started discussing possible materials for the house. I like the concept of using materials in their natural state. I wanted the exterior finishes of the house to be both low-maintenance and to work with nature, not against it. As an example, if you take a yellowish cedar plank and put it outside without any treatment, it will eventually weather and turn a shade of grey. That's what happens to it if you let nature do its work. One can fight nature by applying a clearcoat on the wood every year to keep its color, but at some point, nature will win. I wanted to use something that didn't require that kind of upkeep.

The guys at Pb were totally with me on this idea and they showed me two materials that follow this concept. The first is corten steel. This is a special alloy of steel that is designed to rust on the outside. It's often used in large public works projects and doesn't need to be coated or protected. The oxidized surface acts a layer of protection for the steel underneath. It starts out greyish, but eventually turns to a rich brownish-red over time.

The second material they showed me was charred cedar. This is normal cedar wood that has been torched so that the surface is black. The charred carbon layer on the cedar protects the wood underneath and doesn't fade when exposed to the elements. This technique was apparently used in traditional Japanese architecture.

When they showed me both of those materials, I immediately fell in love with them. It would be a perfect combo for the exterior of the house.

The house also has three other materials which follow the "natural" concept: concrete, aluminum, and glass. Those don't need any other explanation. I think together they compliment each other really well and are all zero-maintenance. The house should actually look better as it weathers over time. That's a new concept!

Here's what it all looks like together:

Second Draft

So a couple weeks later toward the end of August, they came up with a much better second draft, this time with a 3D model!

Many things had changed:

• This version now had three floors, so the room proportions are better (no small rooms with 17' high ceilings). 
• The house also had a wider footprint. The footprint inspired the architects to think of emphasizing the cantilever and create a concept of two mirrored volumes stuck together. It added a lot of character to the house.
• The square footage increased to around 2100 sq ft. While it's a bit large for what I need, I like the wider proportion better, plus it gives me extra square footage if I ever need it in the future
• The stairs to the rooftop deck were moved from the entry area to the rear lower deck.
• A more substantial entryway was added with bridge and coat closet. It is also backed by a set of windows, so you can see straight through the house and get a very indoor/outdoor feel. Cool!
• The bedroom got its own set of doors to the deck
• An office was added with open walls. It gives the possibility of turning it into a third bedroom in the future if I wanted to. 
• The media room was moved to the new daylight basement along with a large storage room/server closet.
• The location of the kitchen and living room were swapped
• A pantry was added next to the kitchen (by request)

At this point, we were all pretty happy with the general layout of the house and the internal spaces. As far as the exterior, it was nice, but was still lacking that wow factor. I thought that the exterior shell of the house could be a bit edgier to really emphasize the shapes, and I think the architects were thinking the same thing.

First Draft

As far as I understand, Pb Elemental uses a design process called "exploratory design". This involves sitting down and cranking out dozens and dozens of variations of a subject, then picking the best ideas out of those and repeating if necessary. It's rather tedious and time consuming, but it forces the designer to explore all possible avenues of a concept and make sure the best possible variant bubbles to the top. All this happens behind the curtain, so my only exposure to it is through a few incremental drafts. 

Toward the end of August, Pb Elemental settled on a the following concept as a first draft. There would be two separate volumes joined together - one going up, the other going down. In this version, the house would be a split-level.

The garage is on the split.

The second floor is cantilevered over the lower floor and is designed to be the main living area. 

Last, there is a set of stairs leading to a rooftop deck. There would be a large, sloped skylight over the living area, and a green roof over the bedroom. 

The house had around 1600sq feet not including the decks and garage. This design incorporated many of the requirements I asked for, set up a general concept for the spaces in the house, and was enough to get a conversation going. 

I thought that the concept was great start, but it had some flaws, as expected and forewarned. The proportions of the rooms on the bottom floor were a bit off (ceilings too high for the size of the room), and the house was a little narrow for the lot. I would have a useless 5' strip of yard on the left side of the house. 

I made the request to increase the width of the house to take advantage of that strip, knowing this would push up the cost of construction. I think this was the right decision to make, even though it would lead to some tense moments during financing later on.