Three reasons not to build a house on permafrost
- Permafrost is unstable ground. No matter how much gravel and insulation you put under your house it is still likely to move as the result of effects of permafrost subsidence.
- Permafrost seems cheaper than good, solid, well drained ground. , However, the cost of buying permafrost land is less expensive but the development is expensive over the long term. Septic systems for permafrost soils are expensive and prone to failure.
- Permafrost is a bad investment because in the end the structure you build may not be worth what you put into it, be hard to sell because everyone knows the permafrost is melting, or it might just fail.
Read more about problems building on permafrost and the cost of building on permafrost below…
Permafrost may seem cheap because it costs $2,000-8,000 per acre (paying more than $8,000 per acre for permafrost is generally too much) and with the uncertainty at UAF there is a firesale on cheap land.
Additional costs associated with building on permafrost for best results.
-Typar fabric rolls
-One hundred feet of driveway will cost $2000-3500 if your land is relatively flat and dry.
– 30-40 yards of gravel to make an average large cabin footprint is 16′ x 24′ x 3′ deep will run $8,000-10,000
Even if the additional costs I have outlined to buy and build on permafrost sum less than purchasing better ground then foundation leveling and adjusting costs might be a wake up call. A simple cabin leveling or foundation adjustment in Fairbanks, Alaska will cost $1,800 but can cost upwards of $20,000 – $30,0000. Even after leveling it will likely sink again causing frustration and more money wasted. This scenario is common enough but let’s think about your house now.
If you are going to roll the dice building a new home on permafrost using a compacted gravel pad here is what will happen. Homes built on permafrost have running water which requires a septic system. There are basically two options for septic systems on permafrost in Fairbanks, Alaska: a mounded system above ground or an engineered water treatment system. Both options are bad. The DEC approved, mounded septic is built to fail. I can honestly say that I never hear about these system unless they have failed. No one has ever said that they work for more than a handful of years and even if it lasted ten years, you are still looking at replacing it at a price tag of $10,000-15,000 X 2 (X 3…..). The engineered water treatment system for a 2-4 occupancy home costs $20,000 and up not including the gravel pad and related preparations (let’s say $1,500). These systems will probably settle at a different rate than your home.
Not only are the expense of the permafrost septic system or it’s replacement things to consider when building on permafrost but it is also the connection to your septic. When the house starts sinking that connection is inevitably going to break under pressure. That connection is always spray foamed. The spray foam needs to be cut away and then pipes re-connected. It’s a mess. Some dude will tell you he’s going to install a “flex” connection but it will only work for an extra day before that connection fails again. Second, as mentioned above, your septic system may sink too or flood so it’s not functional. Read more about septic systems and leach fields here.
Another connection that will fail as your house sinks is your electrical service. Buried lines coming from meter poles often pull out of the service panel. It’s no fun lengthening these lines, it’s not cheap, and it can be avoided. This issue applies to any structure getting power from GVEA that is built on permafrost land.
There is one way of building a home on permafrost that can work.
Call an engineer. He or she will provide a course of action for a fee. The course of action will generally go as follows:
- haul in gravel and make a compacted pad as prescribed above ($10,000-20,000)
- drive steel pilings to a depth of 60 feet (most houses will require 12-20 @ $2000/ea.) ($24,000-40,000)
- install steel i-beams and associated bracing (requiring a boom truck and welder)($5000)
- After the septic system settles away from the house or the electrical service entrance is compromised there can be large invoices coming your way
I have quoted two homes with a gravel pad and driven pilings. I did not get either bid because they were too expensive. It was not that my numbers were outrageous but that the owners both thought that building on permafrost would be less expensive. I was asked if I would build one of these houses on the gravel pad system outlined above. I said I would not. The reason I would not build the house only on a gravel is that I could not warranty the house based on the number of failed foundations I have seen or worked with.
Checklist for buying a house that is built on permafrost
- Look closely at the foundation with your own eyes, if you don’t think you can judge then call a knowledgeable friend or hire someone with nothing to gain by you purchasing the home. Don’t rely on any paperwork from the bank.
- If the walls in the home are freshly painted everywhere it is LIKELY a telltale sign that there are settling issues being hidden. No one paints the entire inside of a home to sell it.
- Walk the property and look for standing water, areas that look like they are sinking, outbuildings that are moving, power pole tilting… if something doesn’t seem right, its probably not. Get a second opinion.
- Examine the mortgage closely. Often you will need more money down to buy a home with a non-conventional foundation that has a higher interest rate over a shorter period. The bank is aware that the investment might not work out.
If you do decide to build on permafrost consider building only a cabin with no running water and take the following precautions….
-Try to design your cabin so it only has 4 points to adjust or level from. This method might require larger beams or steel i-beams running from corner to corner but it make adjusting the foundation achievable for you, the cabin dweller. Spending more money on beams that span longer lengths might seem painful up front but in the end you will be glad you spent an extra couple hundred bucks.
-Minimize clearing around the gravel pad. Disturbance to the moss and trees around the home will often quickly deteriorate the surrounding permafrost. In this sense clear slowly and sensibly after your roof is on.
-Do not be cheap with your gravel pad. Oversize the gravel pad over the permafrost so sloughing at the edges does not degrade or destabilize the underlying area, around your pads, and so you can use an extension ladder to install fascia, soffits, siding and access to insulate your attic.
-Avoid taking advice of people telling you that you can build on permafrost for cheap. That could be a financially painful lesson particularly if they convince you to go with fewer precautions. It’s always nice to hear the advice you want to hear but there is often much more value in the advice you were afraid of hearing. Ask your friends who have built homes or bought homes on permafrost to get an honest opinion other than mine.
I have been asked about building on permafrost over and over by friends, neighbors and clients who want to build on permafrost in Goldstream Valley so I created this page for the community I don’t know. With hotter summers and warmer winters we are seeing rapid changes and the effects of permafrost degradation in Goldstream Valley and other low lying areas in and around Fairbanks, Alaska. Good luck out there!