Frost heaving porch

[gbick]

Frost heaving porch

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My daughter recently bought a "fixer upper" house in Waterville,Maine. It has a poured foundation with a full (but damp) cellar. Among the many challanges thusfar, is a barely supported porch. It was added after. The outer side of the 16'X8' enclosed, unheated porch was supported 2' above ground by 3 rod-and-tube type posts. One post has pitched out into thin air and the other two are at serious angles. The door wouldn't close and one window broke due to the uneven settling. The new metal roof that seamlessly covers the house and porch was starting to buckle. I have raised it back into position with a temporary beam and jacks just far enough in from the outer wall to give room for the perminent beam and support. For numerous reasons, setting new posts below the frost line is not an option. After much ponderance, here is my plan. I will attempt to level the very rocky soil under that outer wall. Then, I WILL level it with a layer of unwetted Quickrete (2'X16'). On top of that will go 2" thick foam sheet, again 2'X16'. Four homemade jackposts, centered along the foam, will support a beam under the outside wall. Each jackpost will bolted to the center of an aluminum footplate 2'X2'X3/4" (that I already have from another project) to spread the load on the foam. Will this remain stable through the Maine winters? I will be away for a few days, but look forward to checking on your ideas and collective wisdom. As always, thankyou. Greg.

[egon]

I suspect the jack post will slowly settle into the foam over time.

I'd suggest digging down as deep as possible for the supports. Pouring a solid well reinforced support pad. [ If you use quickcrete add lots of Portland cement ] Support your house beam with adjustable floor jacks that are bolted to the support pads. Place your insulation and waterproofing around the bottom of the floor jacks and over the concrete pads and use lots. An added benefit, if possible, may involve wrapping a temperature activated heat tape around each support pad.

The adjustable floor jacks will give you the option of keeping everything level.

Egon [img]/forums/images/icons/grin.gif[/img]

[jml755]

I would think that anything you do on the surface (or in-ground above the frost line, for that matter) would be prone to movement, while the main foundation sits still. Could be minor, from season to season, thus the adjustable floor jacks may serve the purpose of keeping everything level. Myself, I would try and get 3 posts below the frost line. Is the problem that you can't dig straight down because of the porch header inline with the posts? If so, can you angle drill from outside the wall? Then you could widen the hole until it's under the porch, put in a sonotube, backfill around the tube and pour. Just a thought.

[Pat]

Getting piers below the frost line or on top of solid rock is best. Heating shallower piers is iffy. There were some techniques used in Alaska for houses built on permafrost.

A grade beam supported by piers below the frost line with carton forms under the beam might be a good candidate. The carton forms will decouple the heave and subside motion of the soil from the support of the beam on the piers.

I can't PROVE to you in any amount of writing that your approach can't work but I will say I would not think it would be a satisfactory long term solution.

You need to tie the support system to a part of mother earth that doesn't move. We don't have a big frost heave problem here as our frost depth is 18 inches (for code) but we have plenty of examples of expansive dirt that expands and contracts quite a lot with changes in soil moisture and that is quite similar to frost heave. IN the OKC yellow pages there is half a page of foundation contractors for building foundations. There are 6 pages of foundation repair contractors. There are lots of foundations built which need EXPENSIVE repairs in just a short time. Not much longer than after the contractor gets paid, changes his business name and starts on a new project.

I hope someone has a fast, easy, cheap, low labor, and effective method for you. I don't.

Pat

[egon]

There really is no solution to building on soils susceptible to frost heaving. The method I mentioned of being able to make constant adjustments is labour intensive. The heat method will work but again is not an ideal situation. [img]/forums/images/icons/grin.gif[/img]

Another method would be to dig below the frost line and fill the excavation with a material that does not allow capillary action. Of course this will only work if the water table is below the frost line. [img]/forums/images/icons/grin.gif[/img] [img]/forums/images/icons/mad.gif[/img]

Permafrost uses the exact opposite method. Design is such that the permafrost is insulated to keep it from melting.
[img]/forums/images/icons/grin.gif[/img]

As Pat said, anything less than footings below frost level will be a pain.

Egon [img]/forums/images/icons/grin.gif[/img]

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