Best Cement for Foundation Repair – What Works in the UK
Got a crack in your foundation and wondering which cement will actually hold? You’re not alone. Most homeowners pick the first bag they see, only to discover it doesn’t set hard enough or leaks water later on. The right cement makes the difference between a quick fix and a long‑lasting repair.
Why the cement you choose matters
Foundation repair isn’t just about filling a gap. The material has to bond to existing concrete, resist water, and handle the weight of your house. If the cement is too weak, the crack will reopen. If it’s porous, moisture can seep in, causing further movement. In the UK’s damp climate, a waterproof mix is often a must.
Another key point: many standard mortars shrink as they dry. Shrinkage pulls the repair apart, especially in larger cracks. Look for low‑shrinkage or shrinkage‑compensating products to keep the joint stable.
Top cement types for fixing foundations
1. High‑Strength Portland Cement (Grade 43.5 or 52.5) – This is the go‑to for most structural repairs. It reaches compressive strengths of 43.5 MPa or higher, meaning it can take the load of a house wall without cracking again. Mix it with a good quality sand and a polymer additive for better adhesion.
2. Polymer‑Modified Cement – Adding polymers (like acrylic or latex) improves flexibility and water resistance. These mixes are perfect for cracks that experience slight movement or sit in damp basements. You’ll notice the cured product feels less brittle than plain cement.
3. Hydraulic Cement – If you’re dealing with active water leaks, hydraulic cement sets quickly and expands as it hardens. The expansion seals the gap and stops water from getting in. It’s ideal for cracks near drainage pipes or retaining walls.
4. Mortar with Bonding Agent – Some manufacturers sell pre‑mixed mortar that already contains a bonding agent. This eliminates the guesswork of adding extra chemicals and ensures consistent performance.
5. Waterproof Cement (Cementitious Waterproofing) – When you know the repair area will stay wet, go for a cement that’s specifically labeled waterproof. It contains additives that block water penetration while still offering good structural strength.
How to pick the best one? First, measure the crack width. For hairline cracks (<1 mm), a thin‑set polymer mortar works fine. For wider gaps (over 5 mm), you’ll need high‑strength or hydraulic cement with a backing material like a fiber mesh. Second, consider exposure to moisture. If the area stays damp, choose a waterproof or polymer‑modified mix. Finally, check product certifications – look for CE marking and compliance with BS EN 206 for cement quality.
When you’re ready to apply, clean the crack thoroughly, remove loose concrete, and moisten the area. Mixing to the right water‑to‑cement ratio (usually 0.45–0.55) ensures the cement isn’t too runny or too stiff. Apply in layers if the crack is deep, letting each layer cure before adding the next.
Bottom line: don’t settle for the cheapest bag on the shelf. Pick a cement that matches the crack size, moisture level, and load requirements, and you’ll save time, money, and future headaches.
