How Trees Can Impact Your Build and Cost You Thousands

31st March 2025

Finance & Budgeting Pre-Construction During Construction Post-Construction

Trees can quietly sabotage your build and cost you thousands. Learn how roots, moisture, and even removed trees can impact your slab, site costs, and warranty.

How Trees Can Impact Your Build and Cost You Thousands

When it comes to building a new home, you’re probably thinking about block size, floorplans, façade styles and pricing. But there’s one factor that is often overlooked - trees. Whether already on your block, nearby, or planted by a developer, trees can have a significant impact on your build and your wallet.

In this episode of the Home Building Hub podcast, Colin Bischof and Darren Brennan break down how trees affect your site costs, slab design, and even long-term maintenance and warranty. From street trees in greenfield estates to old gum trees in knockdown rebuilds, this is a must-listen for any new home buyer.

How Trees Can Affect Your Slab

Here are some key ways trees can affect the construction and stability of your home:

• Root damage: Tree roots expand and grow as trees mature. These roots can lift soil, which in turn can lift or damage your concrete slab.

• Moisture imbalance: Trees draw moisture from the soil, leading to uneven moisture levels around the home. One side of the house might dry out while the other remains moist, causing movement.

• Termite risk: Trees can be a home for termites, which can easily move from tree to house.

• Leaf litter and debris: Trees drop leaves and bark that can block gutters and stormwater systems.

• Pipe invasion: Tree roots seek water and can invade weak points in stormwater or sewer pipes, especially if not properly glued or sealed.

Removed Trees - Still a Risk?

You might think a removed tree is no longer a concern, but that’s not the case.

• Engineers consider removed trees for up to two years after removal when designing your slab.

• Soil behaviour changes after tree removal - it can initially dry out, then swell as the organic matter breaks down and starts holding moisture.

• Slab heave risk increases due to this swelling, and your slab design will often require reinforcement.

Even trees removed by the developer before you purchased your block are considered. Engineers use satellite imagery to assess tree history on your lot.

Street Trees and Greenfield Developments

• Street trees planted by the developer can still impact your slab, especially if your home is within the tree’s root zone.

• Corner blocks may face greater impact due to proximity to multiple street trees.

• Engineering response: Includes deeper edge beams or concrete piers to offset potential damage. These reinforcements increase site costs.

Rule of thumb: Engineers calculate the root impact zone as 1.5 times the mature height of the tree. So, a tree expected to grow to 20 metres will be assumed to impact soil within a 30-metre radius.

What If You Plant a Tree After Building?

• Slabs are not designed for unknown future tree growth. Planting a tree close to the house after construction could expose you to future movement and void your builder's warranty.

• CSIRO Guidelines: Refer to the CSIRO guide to maintaining your house slab for best practices. It includes specific references to trees and their impact.

• Warranty risk: Planting large trees near the house without consideration may void your structural warranty.

Final Considerations

• Trees next to or near your home must be considered in slab design.

• Builders may add concrete piers or deep edge beams to stabilise your home, increasing cost by $10,000 or more.

• Welded piers may be used in cases of severe heave risk.

• Engineers will always err on the side of caution to protect the home.

• Removing a tree is not always safer – it can cause more soil movement than leaving it in place.

• Tree roots are mostly shallow (around one metre), despite the tree’s height. Rarely do they grow deep.

• Consult your builder and engineer before removing or planting trees near your future home.

Key Takeaways

• Trees can cause serious slab and soil issues that are expensive to fix.

• Even removed or developer-planted trees are factored into engineering.

• The size and species of a tree determine its impact zone.

• Post-build planting of large trees can void warranties and cause structural problems.

• Always consult your builder and refer to the CSIRO guidelines before making decisions about trees.

🎧 Listen to the full episode here: 👉 How Trees Can Impact Your Build and Cost You Thousands!

Glossary of Terms

Slab Heave: Movement in the house slab caused by expansion of soil, often due to moisture changes.

Edge Beam: A reinforced concrete beam at the edge of a slab, used to support and stabilise it.

Concrete Pier: A deep foundation element that supports the slab by reaching more stable soil.

Root Ball: The network of roots around the base of a tree.

Tap Root: A single, deep root that grows downward to access moisture deep in the ground.

Frequently Asked Questions

Q: Should I avoid buying land with large trees on or near it? A: Not necessarily, but be aware that trees may increase site costs. Always have your builder assess the impact.

Q: Will council street trees affect my build? A: Yes. Even trees planted by the developer can influence slab design and site costs.

Q: Can I plant a tree after my home is built? A: Yes, but with caution. Avoid large trees near the house and refer to CSIRO guidance to avoid warranty issues.

Q: Can removing a tree save me money before building? A: It might seem like it, but removing a tree can actually increase risk of slab heave and require additional slab engineering.

About the Home Building Hub Podcast

The Home Building Hub podcast, hosted by industry experts Colin Bischof and Darren Brennan, is Australia’s premier resource for new home buyers. With weekly episodes featuring special guests, the podcast provides objective, high-quality insights into the home building process - completely free and without sales pitches. From understanding financing options to navigating the complexities of building a new home, each episode is packed with actionable advice and tips.

Explore more episodes at http://www.homebuildinghub.com.au and join our growing community of informed home buyers.

Disclaimer

Whilst we’re all about providing value to you, this article should not be considered as legal or financial advice. It contains general information only and is based on the content discussed during the podcast episode. This information is relevant to the episode’s release date and may not be applicable at the time of reading. Always seek independent professional advice tailored to your personal situation before making any legal or financial decisions.