Planning Your Addition

An addition to your home can provide you with much needed space along with some fine craftsmanship and new functionality that may not have been available when your home was built. Our Portfolio

Solarium Addition Take a look at some of our work. We think you will agree that our attention to detail, craftsmanship and quality are exactly what you want for your home.
We define an addition as a building project that adds living space to an existing structure. If the added space is alongside the existing structure it must have its own foundation. If we are adding up, for example, building a room over an existing garage, then the current foundation must be able to bear the added load of the addition.

Building an addition is very much like building a house, just smaller in scope. The same processes are required and work proceeds in very much the same order. In any organized urban area that has a building code, an addition will require a permit and occasionally a zoning change or exception.

But an addition has its own particular requirements. The big one is that the addition must blend well with the existing house. Sometimes that's a bit of a trick since the materials and techniques used to build the original structure are often very different from those used today.

Basic Rules for Planning an Addition

The Planning Process

Do you know how the design and planning processes work?
Find out all about them in this article.
The general process of planning an addition is the same as planning for any major renovation. But there are some differences. Perhaps the major difference is the perspective. In a typical renovation we are constrained to fit features and functions into an existing space. If we are remodeling your kitchen, for example, all of the cabinets, counters, appliances and other items required for a kitchen must be fitted into the space you have available in a manner that is both visually appealing and functional. The space constraint is the overriding theme of the design.

Planning for an addition typically has virtually no space constraint. We can, for example, design the room to fit the kitchen, rather than forcing the kitchen to fit the room. Which leads to the first rule of designing additions:

The Deck Handbook

Wood deck
Planning to build a deck or porch. See what options are available.
Plan from the Inside Out

It is very common for some designers and homeowners to do the opposite: start planning with a certain size room on a piece of paper, then figuring out what will fit in the room, and how. Sometimes things are just squeezed into the room any way they can be made to fit. Doorways, hallways, closets, etc. can end up in strange places. This, obviously is not the way to do it.

First the Function, then the Style

If you are blending an addition into your home, you want it to have the same overall style as the rest of the house, but avoid letting style dictate Adapting a Kitchen to Human Dimensions and Movement

We blended streamlined functionality with elegant styling in adapting this kitchen to the needs and physical characteristics of its owners.
function. A common tendency, even among experienced designers, is to concentrate on the style elements first, and then try to fit the room's functions into the design framework dictated by the style. This is backward. Function first, then style.

In designing a kitchen addition, for example, a butler's pantry may be an entirely consistent style element for your 19th century home, but may not be the best functional dry-storage solution. If you opt for the style rather than the function, you may end up with a lovely, but dysfunctional kitchen — or at least a kitchen that is not as functional as it could be.

It's a lot easier to wrap style elements around a good functional design that it is to force function to fit around style elements. First the function, then the style is the approach that produces the best, most user-friendly, designs. Bedroom Computer Station in the Capital Beach Area. Basement Computer Station A critical part of any design is accurate visualization. Our computers generate true-life full-color photographs of what finished rooms will look like, including lighting effects.

Be Flexible: The Rules are Made to be Broken

The third rule of designing additions is that the first two rules can and should be broken when appropriate. Sometimes there are space limitations that do have to be dealt with — for example lot setback requirements that limit how wide an addition can be. And there just may be style elements that are on your "must have" list. If, for example, one of the motivating reasons for adding a kitchen wing is to find space to incorporate your grandmother's baking station (complete with enameled table and zinc-plated flour bin), then that's what we will incorporate. There are better functional solutions to providing a baking station, but this is an instance in which style should override function.

Continues...

Whole Wall Insulation

Insulation is rated in terms of thermal resistance, called R-value. “R” simply means "resistance" to heat flow. Its calculation is quite complex, but for our purposes what we need to know is that the higher an insulation’s R-value, the greater its effectiveness at blocking heat transfer.

R-value rating for an insulation material rates only the material itself. A 4" batt rated at R-12 simple states the resistance of the batt material. It does not rate the entire wall in which the batt is installed. This is commonly referred to as the "Center-of-Cavity" rating.

A more accurate way of measuring thermal loss is to install the material in a wall and then measure the thermal resistance of the wall including its necessary framing members (but not windows, corners or joints at roofs, foundation or floors). This is the "Clear-Wall" R-value and it is almost always lower than the Center-of-Cavity rating.

In a recent study of wall insulation ratings, the Oak Ridge National Laboratory has developed a more accurate rating that it calls the "Whole Wall" rating.

According to the study, measures of "Clear-Wall" and "Center-of-Cavity" thermal resistance are misleading because they do not take into account all of the possible framing material "thermal shorts" through the insulation. A short is simply a place in the wall where the insulation is interrupted by other materials. A stud in a conventional wall is a short, as is the gap left for an electrical box.

Oak Ridge proposes an R-value rating for the entire opaque wall (not including windows and doors) to measure the thermal performance of not only the insulation and structural elements, but also typical envelope interface details such as intersection with other walls, floor, foundation and windows. The standard also considers such previously ignored factors such as moisture resistance (the insulation value of some materials when wet degrades considerably), thermal mass, and air infiltration resistance (heat moves with air).

Using its new rating system to study the effectiveness of various insulation materials in typical house walls, the Laboratory found large differences between the nominal ratings of insulation and its actual thermal performance in a wall.

The best performer was insulated concrete forms due to the excellent thermal resistance of the expanded foam exterior combined with the thermal mass of concrete interior of these structures. The next best was structural insulated panels. A 4" SIP wall was found to be more effective at blocking heat transfer than a 6" conventional stud-framed wall and with 15 times less air infiltration.

To read a summary of the study report, go to the ORNL Building Envelope Research web site. To calculate the R-value of the insulation in your home, use the ORNL Whole Wall Thermal Performance Calculator. The results will probably surprise you.