Estimating Home Building Costs


how to estimate home building costs

What it Cost to Build a House - plus notes on working with your inspector (see 1/2 way down the page - Building Permit Notes)

"What does it cost to build....?" The most often asked question on this website. 

This is a practical discussion about cost estimating. Here is a more important and more foundational look at the Right Amount to Spend on a House.

Use this short article to estimate your building costs. Building and materials cost vary depending on what you put in to the house and the simplicity of your design. While this will vary by location and personal choices, the most obvious determinate of cost is the size of the building. So, we will estimate construction based on the total square footage of the structure. Use the outside dimensions to determine the size and add all the usable floor area that will be finished for living space.

Construction Cost Notes

We built our simple owner-built flat roofed cabin for $10/sf using new materials except for the windows and doors we already had. That was several years ago so this would definitely be at the lower end today. This is for an insulated rustic cabin without wiring or plumbing but with a simple wood interior. The gable roof cabins with a loft would cost somewhat more. A good estimate for such a structure might be $15-20/sf for materials assuming you buy carefully. Check the Gallery of houses where owners have shown pictures of their projects. Many have information on their costs. For an inexpensive house see: This one and This one.

The upgraded 14x24 Builders Cottage, Victoria's Cottage, the Grandfather and all the 20' wide houses all have upgraded foundation options, 2x6 walls and better insulation and windows. They also have full plumbing and wiring, of course. These buildings can be expected to run about $35-45/sf for all new materials. The average cost for cabin and cottage construction, contractor built, is about $70 to $95 per square foot (house only). So an owner-builder can save almost 1/2 if they have the time and experience. Note that there are also wide regional variations, especially in labor costs.

Our members often report back on their costs in the Owner-builder forum

Here is our Quick Cost Estimator for pricing an initial floorplan and any options the project might involve. To use this you need to have an idea of your local base line living area cost per SF. You can ask building officials, builders or building supply houses to get an idea of what conventional construction is costing per SF in your location. This will be a standard contractor built price for a house about the size you are planning to build.

If you are going to be doing some part of the construction yourself, you can reduce this figure (the SF cost) 10% to 50% based on your expected involvement. (Contracted costs are about 1/2 materials and 1/2 labor.) Thus to get a 50% reduction in the total cost per SF you would be expecting to do all the labor yourself.

Use your projected living area cost and multiply it by the main living SF area:

• Count all floor areas over 5' of headroom that will be insulated and heated.
• Count the area of the stairway only once. 

Now, calculate the area of any additional items below and estimate them by using their factor as a multiplier of your main SF cost. Adding these all together will give you an initial construction cost estimate.

For example: If your partially owner-built living area cost estimate is $70/sf, then your unfinished basement will cost (70 x .3) = $21/SF

House Element

Factor

Porch (covered), screen or sunporch

.30 to .40

Carport or enclosed garage

.35 to .50

Attic storage

.20

Open wood deck

.20

Patio and paved areas

.16

Basement w/ wiring & plumbing

.40

Unfinished basement

.30

In addition to the house construction there are site infrastructure costs that are somewhat independent of house size — water hookup or well, driveway, septic system, power connections, etc. These are normally included in the general construction costs estimated initially from local builders. However, if you have unusually high site development costs (perhaps a long road or difficult well) add additional expenses for that.

Estimating Materials

Some of our houses now have an optional materials list and some do not. If one is not yet available for the plan you want, consider taking your plans to a local lumber yard as they may be able to do a free takeoff and cost estimate of your project with the expectation you will order materials from their yard. If you will be working with builders, you don't really need a materials list, as most do their own takeoffs for each stage of the project.

Building Permit Notes

All our plans supply you with all the blueprint drawings and details normally needed for building permits. You may copy any CountryPlans plan set locally to have additional sets for your own (single house) project - you do not need to order multiple sets. On some of our plans you will want to add in some of the included options to customize your plan set before submittal. For instance, you may have several different foundation plans in the set you are sent. You will use only one when you submit your project.

Our drawings may or may not meet all of your local requirements. Code interpretations vary widely and no stock plan will be right for every location. Some locations have specific special requirements such as high snow loads, wind loads, and earthquake loads. Some jurisdictions will require that ALL plans are stamped by an engineer registered in that state. Some building departments will not allow all the foundation options we include in our plans, particularily the pier and beam foundation. The Little House plans with its low impact foundation may not be appropiate for hurricane areas without additonal holddowns.

In short, you may need to modify your plans to satisfy local conditions or opinions. This is true of any stock plan you would buy and even custom home designs you have done by a local architect. Contact a local home designer, engineer or architect if you have required structural modifications. Smaller items such as extra hold-downs can often just be added as written notes on the plans right there at the permit counter. This is what most builders do - just draw on the two sets that are to be submitted at the permit desk.

Any stock plan, modified plan, or owner-designed plan should be reviewed by a local building professional to make sure it meets local codes and climate requirements. This is standard boilerplate you will find on any plans. We go a step further and include information in your plans packet on how to work with the building department and how to ask for a "presubmittal review" to see if you need to make changes. (This can save a lot of time.)

Finally, you can expect any approved plans to come back marked up with some additional notes added. Many of these are things you or the subcontractor would do anyway.

The building permit process and can seem frustrating at times, but is actually helpful to you as an owner and is done primarily for your own safety and the longevity of the building. A good building inspector can help you do a better job of building your house  — so try to see them as a construction resource (which you have already paid for in the permit fee!)

Get Involved with Building your own Shelter.

There is much to learn about the design and building of a house (see our Best Books list). Getting all the bureaucracies satisfied so you are ready to build can sometimes be frustrating! Then there will be all the subs to organize and schedule. Many people love this interaction, negotiation and team working, and some don't. Instead, they can hire a local builder or designer to handle the interface with the building department and perhaps with the subs as well. See our article on 5 Ways to Build a House. You can still be an involved owner-builder AND get help from others! Don't do what doesn't feel right or isn't enjoyable. Houses are much happier places to live in if the people building it had FUN (and were therefore flexible, inventive and perhaps even whimsical)!

Getting a stock plan that comes close to meeting your needs and then modifying and building that plan with local help is a reasonably inexpensive alternative to spending 10% of your total budget on an architect and 20% of the construction budget on contractor overhead and profit. See this article on How to Customize our plans.

Working up an exciting design that meets your space and budget needs is one of the first and most important owner-builder projects you will do. It becomes the foundation of everything that follows. But, don't get too tight about planning every detail. Opportunities will show up that were not put down on paper and could not have been anticipated. You need to jump on these and let the house evolve its own character and direction. Many of these unanticipated changes will be things people will love about this house long after you are dead. So lift your head up every so often and look around.

We make our plans easy to customize because we think you will build a better house by staying awake to opportunities and getting involved. Here's to FUN and SUCCESS on your project! And don't forget the Forum. We are here to help and we love to hear about your project. Check out the Gallery if you haven't already.

how to estimate home building costs

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What small homes cost to build and how to work with the building inspector