YS Development 41st Lays the Foundation

Now that the excavation is complete it’s time to move onto the foundation walls that will support the first home at the YS Development Bellevue 41^st project.   The opportunities for thoughtfulness and forward thinking start from the beginning of any building project and in keeping with this philosophy YS Development is using a special concrete mix which has 50% recycled slag content (a byproduct of smelting ore).  Not only is this an excellent reuse of otherwise waste material it also results in concrete strength close to double that of the more traditional concrete mix. Additionally, special attention is given to preparation of the foundations forms including placing the necessary pipes for electricity and plumbing inside the foundation walls at the time of pour to avoid having to drill the foundation wall in the future.   

A typical foundation is generally made up of two components: the footing and the foundation wall itself.  The footing is a pad of concrete above which the foundation walls will be formed and subsequently poured.  The footing width and thickness is determined by a number of factors including stability of the soil, the height and thickness of the foundation wall that will rest upon it, and the load that foundation wall is engineered to support.  The foundation wall is determined by the footprint and design of the home and the height of the foundation walls is largely a function of the depth necessary to get below the frost layer and by the topography of the site.

Both the footing and the foundation wall are reinforced with steel (rebar) to provide additional strength to the concrete.  You will see in the images that as the footing forms are set they are filled with steel in an orientation that will not only provide the greatest amount of support, but that the steel actually protrudes from the footing form itself.  This will enable the foundation wall when it is constructed to be structurally tied to the footing beneath it. 

After the footing is poured and the forms removed, it is time to start constructing the foundation wall forms and subsequently filling them with more reinforcing steel.  This reinforcing steel is tied with wire to connect it to the steel that was embedded in the footing; creating one solid steel reinforced foundation structure.  Now it’s time to bring the pumper trucks back onto the site and fill the completed foundation forms with concrete.  After the concrete is poured a worker comes by and repeatedly sinks a vibrating wand into it to make sure that every nook and cranny is evenly filled and that there are no air bubbles. 

A few days later the concrete is sufficiently set and the forms are ready to be removed revealing the first permanent structure on the site; the very structure that will be in constant service supporting the framing, roof structure, and every finish detail that will be added to this home over the course of the next several months.

 From a green building perspective it’s important to note the special measures that are taken during excavation and foundation work in order to minimize site disturbance and retain native conditions as much as possible. These include avoiding soil compaction by limiting heavy equipment to the building footprint and construction cntrance, to plan and post restricted areas on site, protect the topsoil on site for reuse, and to preserve the existing native vegetation whenever possible for use as future landscaping.

As the construction process progresses we will continue to follow along.  If you have any questions about any of the steps along the way please get in touch.  We would be happy to provide you with clear answers.  If you would ever like to take a tour of the site we would be happy to make the necessary arrangements.  If this is the first post you have read in our series of green building posts following the construction of green homes, please take a few minutes to review past posts.  You can search the terms Seattle Green Building and go from there.