What you need to know.
As an addition
Some homes have an entrance straight into the basement from the outside; sometimes they are added after the fact. Building a basement walkout is tricky business and could lead to some issues you should be aware of if you are considering this type of renovation.
Some of the common problems may be related to:
- Frost
- Steps and railings
- Drains
- Door thresholds
- Retaining wall problems like:
- Cracking
- Leaning
- Bowing
- Spalling
Frost Protection
In freezing climates like ours, these walkouts need to be built very carefully to ensure adequate frost protection. Once you have excavated for the new walk, you have lowered the effective frost line which may cause frost heaving to affect the structure. When adding a basement walkout, underpinning of the existing foundation is recommended. Another common way is to heavily insulate the walkout excavation with rigid insulation before construction, this will slow the rate of frost penetration (if done correctly) and prevent heaving problems.
Implications to not considering the frost depth can cause structural damage to the home, and safety of residents when using the walkout.
Steps and Railings
Steps must be installed correctly and have a slip resistant surface. Railings must be installed for safety reasons.
Drainage
Drains are need in the floor of the basement walkout, because snow and rain will accumulate there. This drain is connected to your plumbing waste system – not the perimeter drainage.
Exterior type drains should not have a p-trap outside, this is because the water in that trap would freeze. The drain should be manifolded into basement floor drain above the p-trap.
Some conditions that may arise are:
- Missing drains
- Implications: The basement may flood; door may be damaged from accumulated water.
- Clogged
- Implications: The basement may flood; door may be damaged from accumulated water.
- Undersized
- When installing walkout drains, pipes should be a minimum of three inches in diameter. Smaller pipes will be more likely to clog and may not be handle a sudden downpour.
Door Thresholds
A basement walkout should have a four to six-inch-high concrete threshold, this will help prevent snow and water entering the basement.
Retaining walls
Before we consider frost, wet soil exerts more pressure than dry soil; poor design or construction practices may result in a wall that isn’t strong enough. This may lead to structural failure of the walkout walls.
