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An Alameda Foundation Contractor's Insights About Basement Dig Outs and Renovations
Basement Renovations can be great projects, adding substantial new living space to your home. They are, however, much more complex and expensive than most people realize. And this is why.
The Dig Out-
A typical dig out has an existing crawlspace with around 3’-6’ of current height above the dirt. Sometimes there is an adjacent unfinished basement with a lower than normal ceiling height. In order to achieve an 8’ ceiling height in the new space, which is recommended for most projects (habitable minimum is 7’-6”) the dirt needs to be excavated to 9’ (to accommodate for a new slab and base material). Dirt also expands when excavated to about 1.3 times its volume. The amount of excavated dirt is huge, and often has to be removed manually (with small electric jackhammers) when there is no access for heavy equipment. On a couple of projects we completed recently, we were hand digging for over a month and a half with a crew of six, removing about 25 dump truck loads (250 cubic yards) of dirt.
To put this into perspective with wet dirt weighing around 2600 pounds per cubic yard, we are looking at around 650,000 pounds of dirt! That’s over half a million pounds of dirt and several times the weight of an average house. The severity of the amount of dirt removed is probably the primary reason driving the length of time, amount of labor involved, and ultimately the cost of the basement dig out.
The foundations are now engineered, requiring additional excavation for footings and keyways, which have increased with current code revisions, along with substantial reinforcement. This picture shows a new 6’ tall Alameda foundation retaining wall and the extensive footing and rebar requirements. The second photo show a completed dig out.
A common misconception is that we are installing new foundations dug down on the inside of the old foundation, which is left in place. In most instances, the existing older un-reinforced concrete with improper dimensions and issues with creating proper long-term drainage solutions make this a poor approach. Generally, the building needs to be supported and new foundations and drainage installed. The new foundations become foundation retaining walls which are substantially taller than the current walls due to the new height- averaging 4’-5’, or more on a sloped lot. A comprehensive drainage system needs to be installed around the perimeter of the building, consisting of French Drains and downspout drainage.
The Remodel-
The remodeling process for a new basement is comprehensive, time-consuming and expensive. Rough basement spaces and crawlspaces are not set up as finished areas.
Utilities run willy-nilly and in the middle of what will be new finished spaces, so it is typical that most of the electrical, plumbing and mechanical systems for the house need to get either substantially altered or replaced. Often the mechanical systems are relocated to a separate area where they can be consolidated and made more efficient (AKA a mechanical room). Sewer lines often need to get completely replaced, often out to the street for new bathrooms. New water lines, new gas lines, new heating and/or AC, and generally a new electrical service need to be installed. Beams often need to be engineered and installed to open up new spaces. Concrete walls need to be insulated and waterproofed on the interior so the basement walls don’t get damp. Exterior steps and landscaping are often affected, requiring changes outside. New windows need to get added. If access to the main house is included, new interior stairs can be a challenge. The first photo below shows a remodel in the framing stage, the second photo shows a completed basement unit.
The bottom line is that these are massive projects. The structural work takes 3 months on average, with the remodel often taking longer with a total project time of around 6-9 months depending on the complexity of the remodel.
In terms of rough costs, a typical basement project runs around $500-$600 per square foot (depending on the complexity), with about half of that for the dig out (structural work) and the rest for the remodel. Unfortunately, the average client believes these projects are much less expensive and elaborate. Scaling back on the size of the basement will obviously help cut costs, but with a smaller job the price tends to creep up a bit due to the large amount of fixed costs. There are not a lot of contractors experienced with this type of project and who have done enough of these jobs to understand their economics. To undertake this project without the proper funds and using a Contractor who tells you that costs are substantially less could leave you with an unfinished house propped up in the air and a major nightmare on your hands.
Now that I have given you the bad news about cost, there is a light at the end of the tunnel. Given the high value of Bay Area real estate, these can be viable projects when
you consider you are adding new square footage to your home that will significantly increase its value. But hopefully this article will reinforce the fact that these jobs are not for the faint of heart and need to be undertaken with their true costs and complexity being considered early on in the process.
Oakland, Berkeley and Alameda Foundation Projects
Your home’s foundation is incredibly important and when repairs or rebuilding is needed you need a reliable, experienced Alameda foundation contractor to provide long-lasting work and accurate, up-front pricing. Jim Gardner has been serving Oakland, Berkeley, Piedmont, Orinda and most of the East Bay area with high quality solutions to foundation, drainage, and retaining wall problems for over 30 years. If you are in need of a reliable and knowledgable contractor to help you assess and remedy a problem with your home call us today or submit an estimate request from our website.
This article was written by Jim Gardner of Jim Gardner Construction Inc. Jim is a long- time Piedmont resident and has been doing structural repair in your neighborhood since 1983. To schedule an estimate or for more information please go to our website at jimgardnerconstruction.com.
