Thursday, January 27, 2011

Concrete foundation: Phase 1 complete

Phase 1 (of 3) is now complete on our concrete foundation!

First, 1/2" rebar was bent and cut to reinforce the footing and to add vertical tie-ins for the stem wall (to be poured later).

I ran two lengths around the perimeter consisting of four 20 ft sections and some scrap I scored free from Craigslist. To get the rebar off the ground, I could've used metal "chairs" or concrete dobies but opted for suspending it with wire and wood.

Every 4 feet, I put in a small horizontal section and then a vertical L shaped piece that is the tie in for the eventual stem wall.
With the rebar in place, yesterday in the wee morning hours to beat the freaky unseasonable heat, Kendra and I got to work mixing, pouring and troweling concrete for the foundation's footing.
Getting the right consistency. Also, Weber grill on pile of rubble....ya
We ended up using around fifty 80lb bags. Total pain in the ass to move that kind of weight around! 4000lbs lifting in the store into the cart, cart to the car, car to the backyard, backyard to the mixer, ugh. Ok enough whinging haha
Carefully eying the changing consistency. Lots of emptied bags
We got a good system going where I'd be busy lifting and mixing bags while Kendra moved the concrete where it needed to go and troweled.

After it was all laid and roughly troweled (doesn't matter how it looks, just need to get out any voids), we laid plastic down to keep moisture in and prevent drying. The slower the concrete drys, the better; if it dries too quickly, its prone to cracking and is more brittle.
Today we uncapped the plastic and behold, our new concrete moat!

The footing is approximately 16" wide (a bit wider on the load bearing ends) and 8" deep. Should be plentyyy of support for our tiny house.
Next phase, chalking out lines for the final layout, bending and cutting more rebar, building the form for the stem wall (not looking forward to this) and then finally pouring the stem wall.

Stay tuned :)

Friday, January 21, 2011

Framing sketch and design updates

Tiny house framing in SketchUp
Been messing around with SketchUp a bit more and made the above framing sketch. I'm still not exactly convinced investing time in sketches pays off, I was after all getting by just fine with paper, but it is fun to play with and visualize three dimensionally.

I should also update you on the various design changes made: I've scrapped the staggered stud arrangement. I still like the idea but its needlessly complicated for this project. I'm instead going with run of the mill 2x4 studs at 16" and to prevent thermal bridging, I'l have 1" of rigid foam sheathing over plywood. A side benefit of the foam board is that it will act as a drainage plane so I won't need a Tyvek type building wrap.
Second big change I've made is no more monolithic pour slab on grade. Its great in theory (I love the one step process) but for what we have in mind, it just wasn't the right choice. To make it work for us we would had to have laid foam board around and under the entire foundation. I was particularly concerned with placing foam board directly under the concrete footings supporting the weight of the structure. I was told by a foam board manufacturing company that their stuff is rated for such an application but it still left me feeling shaky about the idea. I just can't help but wonder what if that foam degrades over time? Direct contact with the soil for years could potentially take its toll; moisture and termites and the like. So instead, the foundation will be a standard footing with a stem wall (3 pours instead of 1, ho hum). Then we'll prepare the floor slab by first laying down a vapor barrier, then 2" foam with a beveled edge (the picture below will explain this).

Doing the floor slab this way we'll be able to make our own custom tinted concrete mix with plenty of excavated soil in there (no cost filler and a little extra insulation)

Yesterday I picked up some 20ft 1/2" rebar and had a terrifying ride home in my compact truck with 5ish feet of metal poking out the back with a couple whimpy red flags attached; kept imagining someone getting impaled by my rebar everytime I stopped at a light.
Spent most of today bending, cutting and tying rebar and positioning it in the trench. I've run two lengths around the perimeter and have several L shaped vertical pieces to tie into the stem wall.

Pictures and more coming up after we do the pour!

Wednesday, January 12, 2011

Why this will be a slowww process

This may not be a project where every day something new gets done; possibly not even every week.

Foremost, we have the weather to contend with; Northern California is getting their annual dose of rainfall right now. Some rain here and there shouldn't hold up progress on the foundation pour though, it will actually help keep the concrete from drying too quickly. I'd like to finish the foundation during the winter and then once the rain lets up, begin framing.

Then there's the array of projects we've insanely started. We're building some new raised beds in our side yard with a mix of compost and soil excavated for the tiny house. Lots of stones so lots of tedious sifting

We've also been getting seeds started for our winter garden, it's a little bare right now,

and we've been finishing our chicken coop/fortress

Big side project I'm working on is converting the main house's basement into a bicycle shop. Been slow progress on this project also but I'm getting there. Bike season doesn't really start until it gets warmer so I have time anyway

The only other thing that delays the process is me constantly going back and forth about ideas. As I've said, this whole design is not ironed out, so day to day Im thinking about my options. Do I want to do the green roof or do I want a simple lightweight metal roof. Do I want footers and a stem wall or do I want a monolithic pour. Roof slope forward or back. On and on endlessly. It would be great to have a construction minded buddy to bounce ideas off. There is definitely not a set way to build a house

Thursday, January 6, 2011

Design details

Details are still a bit slim honestly but here's some stuff we were thinking

I just started learning how to use Google Sketchup so this is terrible but it gives an idea

In the interest of simplicity, we've chosen a shed roof...but may end up making it complex anyway by making it a vegetated roof (aka green roof). A vegetated roof would greatly increase the life of the roof waterproofing (possibly indefinitely) but its, as said, more complex and its more expensive. On top of that, I the builder/architect/engineer need to be mindful of the additional roof load (especially when wet) and build suitable support for it.
Another possibly stupid complex idea I had was to use a staggered stud arrangement. Picture explains below:
This method is a compromise between traditional 2x4 stud construction and 2x6 "advanced framing" construction with the added benefit of reducing thermal bridging; you'll notice that none of the studs extend from the outside to the inside, there is always a gap that can then be filled with insulation greatly increasing the performance. The cost is of course using more 2x4s than traditionally and some added general complexity, especially for openings like doors and windows. Id space the studs every 12" on center on the stagger which would be every 24" on the interior/exterior. Another plus is all this lumber would surely support even the heaviest roof loads.

Our little Sketchup drawing shows a rough layout of what we'd like, small kitchen area, micro bathroom with composting toilet, sleeping loft and a small seating area.
We'd like to maximize solar heat in the winter so we're putting a big glass double door and a big window on the south side.

All of this is incredibly rough, nothing set in stone yet, but at least some direction to march forward in.

Construction of the tiny house begins

Welcome to our tiny house blog where we hope to chronicle this adventure from start to finish.
My girlfriend Kendra and I (Dan), have embarked on this project to give us our own private living space outside the main communal house. We're in our mid 20s and live in the beautiful San Francisco Bay Area. Both the constraints of our rather small lot and our interest in living simply led us down the tiny home path. Both of us have zero background in construction so we're learning as we go with generous amounts of help from the internet and our local library. It will definitely be a challenging road ahead but we think we can do it!

So we've decided on a 12x10' concrete slab on grade insulated with 2" rigid foam.
The photo above shows our progress thus far clearing the land (including that giant tree mass pictured) and digging footers and raising the slab height level and 6" above grade. Judicious amounts of tamping later, there it stands.

Next step is to layout the foam, support it with rebar or lumber so it acts as a concrete form, then start pouring concrete. We'll be bringing in an electric mixer and mixing bagged concrete; hopefully that works out fine.

Not a great picture but here's what the concrete covered yard used to look like over there (and me cutting up a door for a work bench project)