I recently published a piece on post-tension slabs, which is more used in new construction, however it’s not the most common type across existing homes in the South Bay. While basements are not often found in the South Bay, crawlspaces are. You’re most likely to encounter raised perimeter foundations.
What is a Raised Perimeter Foundation?
A raised, perimeter, or raised perimeter foundation is one that supports a structure while lifting it a few feet above the ground level, as the name implies. It is called a perimeter foundation because the exterior walls are held up by a reinforced concrete stem wall, while the body of the house is supported by a post and pier construct. (In earthquake-free parts of the world, the stem wall may be brick or cinder block.)
This type of foundation is usually only raised around 1-1/2’ – 2’ high, one or two stair steps above ground level. Much taller would make a top-heaviness that becomes less stable against seismic force.
Alternatively, some floors might be set quite low. Two rooms in my single-story house are a step below the rest. They are still raised on posts and piers, but they are distinctly lower than the rest. This is called a sleeper floor. In the crawlspace, this translates to very tight quarters, and I have met professionals who will, and who will not, be able to work in that space.
What is a Post and Pier Foundation?
Post and pier, or beam and post foundation, supports a structure by raising it on individual posts distributed evenly beneath a structure. Each pillar of support consists of three parts: the pier, the post, and the beam.
The pier is a vertical anchor set deep in the ground, usually made of concrete (but occasionally other resistant material like steel). The pier rises a few inches above ground level and is attached to a vertical post. The post, or column, is generally foundation-grade treated wood. This post attaches to a horizontal beam, or girder, which directly supports the floor joists. Occasionally, the pier may act as a post and connects directly to the beam, but that is very uncommon in my experience.
Post and pier foundations can be built without the perimeter wall, but functionally it is very different. You will often see decks built this way, including decks that are attached to homes with a raised perimeter foundation. Without the continuous stem wall the cost to construct is significantly less, but the resulting structure is more vulnerable to the forces of nature, to lateral seismic force, and to pests and wildlife. It also has greater airflow beneath, which is good in places with regular flooding, but provides less insulation from below.
Post-tension slab foundations are found in newer homes. Here in the Bay Area, a structure’s foundation needs to withstand not only the load of the building, but expansive soils, and the ubiquitous earthquake. Certain foundations are better at handling these conditions, and are seen more frequently here. One of these which is gaining popularity in new construction is the post-tension slab foundation.
What is a Post Tension Foundation?
Post-tensioning is a technique that was developed and first put to regular use in the 1970s, and approved methods have been published by the Post-Tensioning Institute (PTI), a nonprofit organization, since 1976. Sometimes called post tensioning, or simply PT, this is a type of slab foundation with added reinforcement.
In essence, a slab foundation, aka a slab on grade foundation, is a concrete base only a few inches deep, sitting directly on earth. You might see this for a small shed or playhouse, but larger structures are almost always reinforced, usually with rebar, and a fabric water barrier is lain out before the concrete is poured.
A post-tension slab is reinforced with grids of steel cables cased in plastic sheathes instead of rebar. After the concrete has hardened around them, the cables are pulled taut with hydraulic stressing jacks. This pre-stressing of the concrete creates added compressive strength to the foundation.
Homes which are dark inside, or which feel dark to potential homebuyers, are much more difficult to sell, and virtually always sell for less money than those which are perceived as “light, bright and airy”.
While a property’s owner might love the cozy feeling of dark paneling, deep overhangs and low lighting, it’s not what most buyers want today. To maximize the amount a house, condo or townhouse in Silicon Valley will sell for, it’s imperative to make it as attractive to buyers as possible. In many cases, that means it needs to be lightened and brightened to sell for top dollar.
How to make a darker home a little more light: start with the windows
How can a home owner make a house or home be – or seem – more bright? One of the biggest “offenders” in this area involves windows! Here are a few window-related problems that can make a home feel significantly darker than necessary, together with some potential solutions:
- Tinted windows, such as yellow or other colored glass at the front door or entry way: replace with clear or translucent, colorless glass. If there’s a darkening film (for instance, for privacy), remove it and replace with a clear or translucent but uncolored film instead.
- Curtains/blinds which obstruct part of the window: get tie backs to pull them further back and let more light in (goal is to not obscure windows at all).
- Furniture blocking windows should be moved or swapped out for lower items that do not cover up any of the windows. I see tall headboards often situated right in front of the glass panes – they are counter productive. Perhaps remove the headboard, or place the bed in another location?
- Shrubs and trees covering some of the window: trim back so the window’s glass panes are 100% visible, if at all possible, to let maximum light in.
- And of course, do make sure your windows are sparkling clean!
Silicon Valley has a bad case of “urban sprawl”, unfortunately, but there are places in San Jose and nearby where creeks meander through neighborhoods, offering a little extra space between back neighbors. This extra breathing room is valued by homeowners with a creekside location. They often cite the pleasantly rural sounds of frogs and birds as an added bonus.
But some home buyers are a little spooked. Are there risks with buying real estate next to a waterway? Would the home flood in heavy rains? Is there an excess of unpleasant wildlife to worry about? One of my buyer clients was concerned that burglers would use the creek’s access path to steal things and get away unseen. Another was afraid of cougars or bobcats or other unwelcome visitors coming in from a creek or tributary.
When Jim and I were newlyweds, we lived in a townhouse on Neary’s Lagoon in Santa Cruz (a bird sanctuary) and I have sold several homes along creeks or ponds, so will make some comments based on my experience.
Creeks: scenic or not?
In general, I would say that being next to or near a creek most often will improve the value of the home because creeks are scenic and also provide a space buffer between rear neighbors. They frequently have beautiful old trees framing their banks and are slightly curved, too, so these are usually quite pretty. I won’t say that living next to a waterway which looks like a Los Angeles flood control channel would be beautiful or enhance a home’s value much, though the space between neighbors would still be appreciated. Each case must be judged on its own merits.
Wildlife at the water’s edge
It is true that there will be more wildlife near water, whether it’s a creek, river, reservoir, pond, or percolation pond. Birds, reptiles and animals need water and will seek it out. If you love nature, you may welcome the sound of frogs and geese, and perhaps secretly hope to see a wayward deer! If you decide to live near water, it is very important to make sure that wildlife cannot enter your home (chimney, attic and crawlspace included) and it will require some ongoing diligence to keep them out because they will be drawn to the water over and over again. I’ve known people adjacent to water to have some challenges with birds, bats, mice, rats, and other creatures trying to make their way in. But that can happen anywhere. At our current home, which is not next to or near a creek, we had a squirrel try to claw its way through flashing on our roof to get into the attic. Another time we had a possum or raccoon get into the attic. Be clear that being away from the water doesn’t mean “no wildlife issues” – but if you are next to water, you will probably face them a little more often.
Floods and flood plains
Creekside locations do not all flood; this is perhaps the biggest misconception. When buying a home, you can check the flood plain status via the Natural Hazards Disclosure Report, which the seller provides. And please know that there are different types and levels of flood plains – they are not all the same! The one which requires flood insurance is called a 100 Year Flood Plain and in those locations, water of up to 1 foot may be expected once every 100 years (so not that often). There are 500 year flood plains and areas which are “dam failure inundation” zones (if a dam were to break, water downhill would flood, of course).
Protected species that depend on the waterways
We have a number of protected species in California, including certain frogs and salamanders. If your home (or the one you want to buy) is in the habitat area of those animals, birds, or reptiles, you may have some constraints on landscaping near the creek or water. Most of the time it involves not placing a fence within so many feet of the creek and using only native landscaping in that area close to the creek too.
As for crime, I would have to say that you want to always check a site like CrimeReports.com or similar sources to know what’s happening. We do have crime everywhere, and all kinds, to varying degrees. Most creeks do not have easy access to people’s homes or yards, and often the service road along the creek is a rough gravel, so I have a hard time picturing burglers trying to get in and walk their stolen loot a ways down that path. But check the reports. Realtors are not crime experts and we cannot make promises about any area or location.
If you are buying or selling a home built before 1960 in California, you’ll likely have to get or complete a form regarding earthquake hazards at the home (some people / situations are exempt) called the Residential Earthquake Hazards Report. The is written and mandated by the State of California. Question # 7 asks about homes with a living space over a garage – this is referencing soft story construction. Many home buyers and sellers would benefit from understanding all of these questions and why the responses matter for earthquake safety. Today we’ll focus on the seventh one.
Residential Earthquake Hazard Report for pre-1960 construction
Soft story construction can also related to office buildings or store fronts on the first floor with large windows or doors rather than solid walls and more floors above it.
The danger arises from the lack of sheer wall in case of a quake. The all glass windows on the first floor, or big carports or garages, are simply not as strong as a wall, and may give way in the case of shaking. For that reason, many are bolstered or reinforced. I wrote about it earlier this week in my Move Move2SiliconValley blog, please read more there: Is your home safe in an earthquake?
What is a cripple wall? (on my popehandy.com site)
In Santa Clara County, as in much of California, we have adobe clay soil and it’s expansive. That is, when the dirt gets wet, it expands, and when it dries out, it contracts. Hence it’s sometimes referred to as “shrink-swell” soils. (Every state in the union has areas with this problem – a color-coded map on geology.com shows areas with more and less expansive soils.)
Why is expansive soil an issue for homeowners and would-be homeowners in Silicon Valley?
The trouble is that the expanding and contracting soil is far stronger than concrete and the foundations upon which a home sits. A well written and illustrated six page paper can be found online explaining the mechanics involved for those interested in more detail on the hows and whys of expansive soils. (It states that the ground can life as much as 5,500 pounds per square inch!)
What I’d like to focus on here is mitigating the risks and preventing the problems associated with expansive soils.
The trouble is not so much that the soil is wet or dry. The problem is in the back and forth, the movement. When the soil is kept at an even amount of moisture, it does not expand and contract.
Obviously, rain is seasonal and we cannot control all moisture on or near the house. We can, though, work to move water away from the house and away from the foundation.
Keep rain away from foundations on adobe clay soil!
Winter storms can bring an enormous amount of water onto a home’s roof, and when it channels down gutters and downspouts, there can be a large amount of water exiting in just a few places. Where does that water go?
Most homes in Silicon Valley come with some type of parking space for cars beyond street parking. Home buyers want to know that there will be a place for their vehicles (and often their “stuff” too). Garages and parking are sometimes under-appreciated aspects of evaluating real estate, and sometimes there are parking surprises after the close of escrow, so it will be the focus of today’s topic.
Parking and resale value
Because a real estate purchase is a big ticket item, it is always important to consider the ability to sell it later. (Always buy with selling in mind!) Will the property you have or are considering buying be hard to sell in the future if it is not a red-hot sellers market? Parking can greatly impact “resale value“ and overall desirability to a large portion of consumers, who may look at that space as protection for a beloved vehicle, a safety feature, a future hobby room, or many other possibilities.
If you are evaluating a Common Interest Development (CID) condominium, townhouse, or planned unit development home with private roads and parking, there will be some special concerns that may be a little different than if you were purchasing a single family home. We’ll consider both.
General principle: In all types of housing in the San Jose area, usually the most highly desired type of parking arrangement is an attached garage with direct access into the home and with side by side parking provided (not tandem). This is not true in all cases but is generally true. You would not find home buyers interested in historic homes (Victorian, Spanish, Craftsman) wanting a prominent two car garage at the front of the house, commanding the lion’s share of the view from the street. (So don’t expect to see that in Japantown, Naglee Park, or the the Rose Garden areas of San Jose.) But for the typical buyer of the more common ranch style house, the attached garage is expected and appreciated, and if it’s missing it may be a challenge to sell the property later because the property will be appealing to a smaller pool of buyers.
Regarding direct access: garages are not allowed to have a door entering into a bedroom. This is for safety reasons since bedrooms are where residents are most vulnerable, and garages are an area of increased safety risk.