Frost heaving porch

[gbick]

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'd suggest digging out the footing locations as deep as possible and then pouring a good reinforced pad. [ If you use quickcrete add some Portland for extra strength ]

Bolt adjustable jackposts to the pad and to the support beam. Get everything level in warm weather.

Add your insulation above the concrete pad and for a distance around the pad making sure it is waterproof. Keeping water from the pad area is critical as this is what will create the frost heave.

If feasible add temperature activated heat tapes under the insulation and around the concrete pad. This may prevent the area from freezing.

This should allow you to make adjustments as required if you get frost heaving.