Upgrades to 1969 concrete foundation in maine
I have a 1969 ranch in Maine that has a full basement. I get seepage through small cracks when the ground water builds up. The ground slopes towards the house right now which I’m sure is a large contributing factor.
I want to dig the ground up around the house, seal the concrete from the outside, possibly install drainage, possibly install exterior insulation, and then backfill and regrade away from the house.
I would like to build an office and a play room area in the basement.
Looking for ideas on the best practices to complete this upgrade.
Should I use the normal black concrete sealing products or is there another fluid applied product I should use? I’m using vp100 on the wood framed walls and I know henry has a product for below grade as well but it’s an old foundation and I’m sure not going to be super clean.
Should I retrofit exterior insulation or just take care of it from the inside?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
There is no short answer to your question.
Are you working with a contractor? Even if you rent a machine, this’ll require a lot of trucking.
ABSOLUTELY install drainage. Matting too and appropriate fill.
Yes, the walls will be dirty. Both liquid applied and membrane based water proofing will require you pressure wash.
I’m partial to any product I do not need to apply and warranty and typically contract with a tech to spray apply. Be sure to remove and seal any remaining ties with hydraulic cement prior to water proofing. Liquid will also be more forgiving with any irregularities.
Exterior insulation will require concealing and protection as it moves above grade, and will require a transition at its top. What can your budget tolerate?
Nudura produced 4x8 EPS sheets with embedded strapping- great for interior basement walls.
I still like the old asphaltic waterproofing stuff used on basement walls, but you will need to clean the wall before applying that stuff since it needs to be able to adhere directly to the concrete. Any dirt on the wall will leave little unadhered spots that can fail over time.
I would absolutely add exterior rigid foam here, and I'd use XPS due to it holding up best to water over time when used underground like this. If you don't have perimeter drainage, now is the time to install that too, and while you have the trench open, I'd also put in a seperate drain system for your gutters. Basically use the usual perforated drain pipe down at the footing (ideally slightly below, but at the level of the bottom of the footing is OK too), then use solid pipe up higher in the trench for the gutter drain. Drain the gutters to daylight somewhere convenient on your property, ideally into a drainage ditch, and put in a sump pump if necassary to handle the footing drain. I find that draining the gutters well away from the house often solves many basement water issues.
Bill
I design homes and renovations in Maine and my standard spec for sites with a high water table or that will have living space in the basement is to use either asphalt emulsion damp-proofing in conjunction with a properly installed dimple mat; Delta MS is the most common. My upgrade from that is a high-quality elastomeric compound, and the best is an elastomeric compound with a dimple mat.
In all cases, it's important to include a footing drain below the slab level, and that drains to open air or a sump with a pump and at least one backup pump. I have seen many sleeved, corrugated black plastic drains crushed and/or clogged, so I spec perforated PVC with a separate geotextile filter fabric and 6" of clean crushed stone around the pipe. In some cases I recommend a second footing drain above the first, as backup in case of a problem.