Read This Before Doing a Basement Digout

If there’s one thing I’ve learned in my nearly 40 years as a structural contractor, it’s that lack of preparation and research is the #1 reason homeowners end up getting burned on foundation projects like basement digouts. 

In this article, I’ll tell you about some common pitfalls to avoid when choosing a Bay Area basement digout contractor. 

Let’s jump right in … 

There are couple of paths you can follow when you are digging out under your house to create new living space:

1. Hire a Contractor for the Whole Project

One approach is to hire a contractor for the entire project. This includes the structural and remodel work from start to finish.

The advantage of this is to have a more seamless job with all of the details being considered in the design and execution of the work.

This could be done either with a design-build company that handles everything, or hiring an architect to do the design and having contractors bid the work with a general handling all of the construction.

This tends to be a more expensive solution for homeowners, as most general constructors subcontract out this work. 

2. Hire a Foundation/Structural Specialist for the Basement Digout

The alternative is to hire a foundation or structural contractor to do the dig-out and relevant structural work, and then to bid out the remodeling separately.

Why would you want to do this? For several reasons: 

  • You save money (as much as $50,000-100,000 on larger jobs) by getting more competitive pricing on the remodel work, with clients generally acting as their own contractors and hiring subs, carpenters, etc. to deal with the more detailed parts of the project.
  • You have more personal control over the design and work or to spread it over a longer period of time to keep the budget under control.

If You Decide on Option #2, Here’s What You Need to Know

It’s important to consider the relationship between the initial project and the future remodel, both in terms of what needs to be considered in the initial job that will affect the remodel, and how these projects are viewed by the various building departments and the pitfalls to avoid moving forward.

It would probably be easiest to illustrate this using an example of a project we are currently working on in Oakland …

The owner had an existing basement with an average ceiling height of around 6.5’ that was being used mostly as storage, but which she wants to convert to living space in the near future. She has a plan of how she wants everything laid out: adding a couple of bedrooms, 2 baths, family room, laundry, and garage, and has hired us to do the structural.

We had our engineer draw basic plans for new foundations, drainage and slabs with a new ceiling height of 8’. In our plans we show this space remaining as unfinished basement.

The City of Oakland does not allow you to create new finished space, including things like bathrooms and bedrooms, kitchens etc. (some of which may not be legally allowed due to zoning regulations) without proper permitting. Generally, they will allow you to add storage, office space, utility areas, etc., if these spaces are already partially finished but the ceiling height is increasing, but in our case we just showed it as unfinished basement before and after.

The primary things we had to consider were the locations of future doors and windows and locations of plumbing that would go under the slab (i.e., drain line for bathrooms).

basement digout oaklandIn this project we had the rear door shifting over (affecting the foundation), and we had to install sleeves in the foundation in the areas of the planned bathrooms for drain lines to be done during the remodel. Since we had a basic design of where things were going to be, we were able to determine that we had sufficient height in the locations of the bedrooms for future egress windows required by code.

The new central foundation was done below the slab level to allow for a central wall where we could add future openings wherever we saw fit rather than having to decide now on their exact locations. Instead of adding seismic upgrades now as part of the structural work, that was deferred to the remodel, since insulation, electrical, etc. would be behind any plywood sheer walls that would go in and would require their removal later.

Our experience with complete basement remodels and related permitting issues and how they vary from one city to another allows us to anticipate in advance issue that might come up later in the remodel, or might cause the dig out plan to get rejected by the City up front and complicated and future remodeling plans.

In Summary: How to Choose the Right Bay Area Structural Contractor for You

A well-organized project with the structural and remodel that are separated, can easily save a client $50,000-100,000 on a larger basement job if they want to manage their own remodel project.

But it is crucial that elements are not left out of the structural work that would cause problems later on, or require demo or redo of structural work, particularly if under slab plumbing issues are not considered early on.

And making sure proper drainage is done as part of the work is critical. Some structural designs leave in the current foundations and excavate in front of them to add additional foundation. In this scenario drainage is often ignored … until it causes major problems in the newly finished space in the next wet winter!

My final $0.02: if you’re considering a basement digout job in the Bay Area, talk to a structural specialist

Basement Home Additions – Can You Dig It?

Now that the real estate boom in the Bay Area has subsided, more people are focusing on making long-term repairs and improvements to their existing homes. When these projects involve the creation of more living space, the standard approach has been to build an addition. These are either second-story additions, additions behind the existing residence, or a combination of the two.

Another way to create new space which is becoming increasingly popular is to add space underneath your home, which for lack of a better term we will call the Basement Addition. This can involve the use of an existing basement, or the excavation of a portion or all of the crawlspace to create an entirely new area. There are advantages and disadvantages to either type of improvement.

The Traditional Home Addition

Adding a second-story addition allows one to take advantage of natural light and visibility. Architecturally, these spaces can be very appealing. By going up, you are not removing yard space from Piedmont’s typically small lots. On the other hand, the increased visibility may be an issue for your neighbors. In a community where zoning regulations and neighbor input are looked at carefully, these projects can be difficult to get approved.

Second-story additions almost always require additional foundation and structural work to support the upper level, especially in older homes. The need for a stairway usually requires altering floor space at the lower level. And the rear addition requires using yard space which is not always available in smaller properties, due to limitations on the percentage of structure allowed on the lot or setback issues.

We Come From the Land Down Under

And I’m not talking about Australia! When exterior additions are not a feasible alternative, you can consider using the space under your home. The cost of such a project and the quality of the space developed depend on several factors. In general, the greater the slope your house is on and the more dirt you have to remove, the larger new foundation retaining walls become and the higher the cost. Taller foundations may limit the dimension of windows and will require more creative solutions to build a comfortable space while meeting habitability requirements.

Habitable space (aka living space) must fulfill certain building requirments and is significantly more valuable than non-habitable space (aka storage space) since it increases the total square footage of the living space in your home. In order for a basement addition to be considered living space it must be at least 7′-6′ in height, heated, properly insulated, with enough windows to meet glazing requirerments (around 10% of floor area).

Non-habitable space does not have the same monetary value, but it can be an important part of a basement project. Media rooms, mechanical rooms, wine cellars, laundry rooms, and bathrooms are spaces which do not necessarily require windows (or for which small windows are sufficient). They can be created in the portion of the addition which is mostly below grade (underground), reserving walls with larger window spaces for family rooms, bedrooms, home offices, recreation rooms, playrooms, and so on.

Aren’t Basements Cold, Wet, and Nasty?

Absolutely not, if they are built or remodeled properly. With proper heat, insulation, light, ventilation, and appropriate finishes the basement addition should be similiar to the rest of the living space. Concrete retaining walls tend to make basements quiet, cool, and pleasant during warm weather.

The key to basement projects is the integration of structural and mechanical elements with the remodeling of the new space. Most basement additions require the removal and replacement of older foundations and the installation of a modern drainage system as part of the work. Since most of the house is affected by the structures underneath it, there is more going on in a basement addition than in a traditional remodel. The plumbing, heating, and electrical systems for the house may have to be modified or relocated. Since existing basements are not designed as finished spaces, their framing is often irregular and needs to be modified. Properly addressing all of these elements is crucial in planning this type of work.

The Bigger Picture

At a time when habitable space in Piedmont is valued at approximately $600 per square foot, it is easy to see how a large basement addition can add value to your home. Basement additions will generally address existing structural problems as a part of the work. A full discussion at the beginning of such a project of the issues and alternatives outlined above will lead to the best design decisions and allow the homeowner to compare the cost and benefits of the work as part of that process.

Jim Gardner is a Piedmont resident and contractor whose company, Jim Gardner Construction Inc., specializes in basement additions and structural repair. He can be reached at (510) 655-3409.