Posted by: Karim Ali
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Stone Foundations: Pros, Cons, Repairs
Many homes in Centretown and The Glebe were built in the late 1800s to early 1900s, and a lot of them still have original stone foundations. These foundations have stood the test of time, but they do require proper maintenance and occasional repairs to stay strong.
If you’re living in or thinking about buying a home with a stone foundation, it’s important to understand how they work, their common issues, and what to check before making a purchase. In this blog, I’ll break down the key things every homeowner should know about stone foundations in Ottawa.
1. What Are Stone Foundations?
Unlike modern concrete foundations, older stone foundations were built using limestone, fieldstone, or rubble stone stacked together and held in place with lime-based mortar.
Why Do They Last So Long?
Stone itself is incredibly durable, and with the right maintenance, these foundations can last over 100 years. However, the mortar holding the stones together breaks down over time, leading to moisture problems, cracks, and shifting.
How Are They Different from Modern Foundations?
- No waterproofing: Older foundations weren’t built with modern drainage systems, so moisture is more of a concern.
- More flexibility: Unlike concrete, stone foundations can shift slightly without major cracking, making them somewhat resistant to minor soil movement.
2. Common Signs of Stone Foundation Issues
Not all stone foundations are in bad shape, but if you own an older home or are thinking of buying one, look for these warning signs:
Moisture or Water Leaks
- Stone is naturally porous, so it absorbs water if not properly maintained.
- Look for damp spots, puddles, or white, chalky residue (efflorescence) on the basement walls—these are signs of moisture getting through.
Crumbling or Missing Mortar
- The lime-based mortar that holds the stones together breaks down over time.
- If the mortar is soft, cracked, or missing, the foundation may need repointing (replacing old mortar with new mortar).
Shifting or Bowing Walls
- Some homes have stone foundations that lean inward slightly due to soil pressure.
- If the walls bulge noticeably or have large cracks, this could be a structural issue that needs professional attention.
Pest Intrusions
- Small gaps between stones can allow rodents and insects to enter.
- If you hear scratching in the basement walls, it might be time to seal those gaps.
If you notice these issues, don’t ignore them. Stone foundations can often be repaired rather than replaced, but catching problems early is key.
3. Should You Buy a Home with a Stone Foundation?
If you’re thinking of buying a home in Centretown or The Glebe with a stone foundation, don’t assume it’s in bad shape just because it’s old. Some stone foundations are rock solid, while others need work.
What Should You Check Before Buying?
- Get a foundation inspection: A professional can spot weak mortar, moisture issues, or structural problems.
- Look for past repairs: If the home has had repointing or waterproofing done, that’s a good sign.
- Ask about drainage: Poor drainage around the home can lead to excess water pressure on the foundation.
- Check for musty smells: If the basement smells damp, there could be hidden moisture problems.
What If It Needs Repairs?
- Repointing mortar is a normal part of owning a stone foundation—it’s not necessarily a dealbreaker.
- If the walls are severely shifting or bowing, however, repairs could be costly.
4. The Cost of Stone Foundation Repairs
If your stone foundation needs work, the cost will depend on the extent of the damage and the type of repair needed.
- Repointing Mortar: $5,000 – $15,000 (depends on foundation size and condition).
- Interior Waterproofing: $3,000 – $10,000 (adding drainage and sealants to prevent leaks).
- Reinforcing a Bowing Wall: $10,000+ (if the foundation needs structural reinforcement).
When to DIY vs. Call a Professional?
- Small cracks or missing mortar? You can patch minor areas yourself using lime-based mortar.
- Large cracks, shifting stones, or moisture issues? Call a foundation expert, because these problems can get worse if not fixed properly.
That's All
Stone foundations give older homes in Centretown and The Glebe a unique historical charm, but they do require special care. If maintained properly, they can last well over 100 years.
If you own a home with a stone foundation:
- Check for moisture and cracks regularly.
- Repoint the mortar when needed to keep the stones in place.
- Improve drainage around your home to prevent water damage.
If you’re thinking of buying a home with a stone foundation, get it inspected first. Some may need expensive repairs, while others have already been reinforced and are good for decades to come.
Bonus tips
1
Use the Right Mortar
If you’re doing repairs, always use lime-based mortar, not modern cement, which is too rigid and can damage the stones.
2
Keep an Eye on Drainage
Make sure your yard slopes away from the house and that gutters and downspouts direct water away from the foundation.
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