Quick Answer
Yes, it is possible to add topsoil over existing grass. However, there are some important considerations to keep in mind when doing this to ensure the health of the grass and success of the project.
Overview
Adding topsoil over an existing lawn is a project many homeowners take on to level an uneven lawn, improve drainage, or prepare for new seeding or sod. With proper preparation and care, topsoil can be successfully added without damaging the existing grass. However, inadequate preparation or improper technique can shock, smother, or kill the grass.
Some key factors to consider when adding topsoil over grass include:
- Timing – Best done in early fall or spring when grass is actively growing
- Topsoil quality – Use high quality screened topsoil without clumps, debris, or weed seeds
- Topsoil depth – Add no more than 1/2″ to 1″ at a time
- Preparation – Mow, dethatch, and aerate the lawn prior to topdressing
- Technique – Spread topsoil evenly and work into grass using a rake
- Post application care – Lightly water and allow grass to work through soil layer
When done properly under the right conditions, adding thin layers of topsoil can be a great way to improve an existing lawn without starting completely from scratch.
Should You Add Topsoil Over Grass?
The decision about whether to add topsoil over an existing lawn depends on several factors:
- Lawn condition – Topdressing is most successful if the underlying grass is healthy and thick. Sparse or weak grass may not readily grow through soil.
- Soil needs – Determine if the lawn needs amendments to address compaction, drainage, or nutrient deficiencies first.
- Grade – Adding soil makes sense if attempting to fill in low spots or gradually level a lumpy lawn.
- Time and effort – Topdressing requires proper timing and consistent monitoring and watering afterwards.
- Other options – Alternatives like core aeration, overseeding, or spot leveling may also improve lawn issues.
If your grass is already in good condition, topdressing can enhance the lawn further. But it also makes sense to consider other improving projects first if the lawn is patchy, weedy, or consistently soggy.
When to Apply Topsoil Over Grass
Timing is critical when adding topsoil over grass. Topdressing should be done during active grass growth periods when the lawn can quickly recover from burial and grow up through the added soil layer.
The best times to add topsoil are:
- Early fall – From late August through September, after summer heat has passed but before first frost
- Spring – In early spring after grass breaks dormancy and begins vigorous growth
Avoid topdressing during summer heat or winter dormancy, when grass is stressed and will be slower to respond to topsoil coverage.
The most important factor is soil temperature, which should be at least 55-60°F several inches down for active turfgrass growth. Time applications based on weather conditions in your specific location.
How Much Topsoil to Add Over Grass
When topdressing over an existing lawn, apply no more than 1/2 to 1 inch of topsoil at a time. This thin layer allows sunlight to still reach the grass below and minimizes suffocation.
Thicker layers take longer to integrate and increase chances of issues like:
- Buried grass crowns smothered by soil
- Damp, dense layers that restrict air and water penetration
- Weakened grass unable to effectively grow up through deep topsoil
Additionally, thick piled-on layers are prone to erosion and slipping down slopes before roots stabilize them.
If your lawn grade needs significant lifting, it’s better to apply multiple thinner layers over time rather than dumping extensive topsoil all at once. Wait 4-6 weeks between applications to allow turf to recover and work through the soil.
Topsoil Quality
The quality and contents of the topsoil used for lawn topdressing are very important. Seek out high-grade triple screened topsoil without debris, stones, clods, or weeds.
The topsoil should:
- Have a loose, crumbly texture allowing roots to penetrate
- Be fertile, enriched with compost or organic matter
- Have pH between 6.0-7.0 suitable for grass
- Be free of compacted clumps and sticky clay
- Not contain viable weed seeds or seed pods
Lower quality topsoils may introduce stones, weeds, poor drainage, or toxic elements. Always inspect and ideally test the topsoil before purchase and application.
Proper soil screening filters out debris, break up clumps, and mixes in amendments to create an ideal growing medium for topping lawns.
Lawn Preparation
Proper preparation of the existing lawn is key before adding topsoil. Thoroughly mow, dethatch, and aerate the grass beforehand to encourage active growth up through the soil layer.
Steps for lawn preparation include:
- Mow – Cut grass short to remove any dead material and allow soil contact.
- Dethatch – Thatch buildup impedes soil contact and root growth up into soil.
- Aerate – Core aeration opens up the lawn for enhanced air, water and soil penetration.
- Remove debris – Clear away sticks, leaves, stones that could get buried and cause bumps.
- Apply starter fertilizer – Encourages faster greening up through the soil layer.
Avoid aggressive power raking, which can thin the lawn right before covering it with soil. Focus on mowing, dethatching, and aeration to allow for maximum soil contact.
Topdressing Technique
The actual process of topdressing requires care to distribute an even 1/2 to 1 inch layer across the lawn. Follow these tips for best results:
- Use a drop or broadcast spreader to distribute soil, avoiding clumps and piles.
- Breezy days make spreading difficult – avoid windy conditions if possible.
- Make several passes across the lawn, applying a thin layer with each pass.
- Use a lawn leveling rake to smooth out the layer, working it down into grass.
- Avoid repeatedly walking on newly topdressed areas to limit compaction.
- Finish by using a push broom to sweep off any excess from sidewalks or drives.
Pay close attention to slope and grade as you work to maintain a smooth, consistent layer over every part of the lawn.
Caring for Topdressed Lawns
Special care is needed for 4-6 weeks after applying topsoil over grass to encourage the lawn’s recovery. Proper watering, fertilizing, mowing, and monitoring ensures success.
Tips for post-topdressing lawn care:
- Light, frequent irrigation – Keep soil moist but avoid overwatering. Go for short, daily sessions.
- Delay fertilizing – Wait 3-4 weeks, then apply turf starter fertilizer to stimulate growth.
- Mow lightly – Be careful not to scalp or disturb the grass-soil interface.
- Overseed if needed – Add grass seed to fill in thin or bare patches for full lawn coverage.
- Watch for issues – Monitor for puddles, poor drainage, or grass decline indicating problems.
With attentive care through the first month, the grass should stabilize the soil and grow up to achieve a level, healthy lawn.
Troubleshooting Problems After Topdressing
Occasionally issues can develop after topdressing over an existing lawn. Being watchful for potential problems is key. Some common challenges include:
Uneven growth
If grass grows inconsistently, with patchy areas of thicker or thinner turf, it indicates uneven distribution of the topsoil layer. Ensure an even 1/2 to 1 inch layer across the entire lawn.
Water pooling
Low spots that collect water suggest the grade is uneven or drainage lacking. Probe any soggy areas and fill with extra topsoil if needed to level.
Compaction
Step firmly on the lawn in a few areas. If the soil feels dense and hard underfoot, additional aeration may be required to loosen compaction.
Thatch buildup
Excess thatch will impede soil contact and root growth up into the new topsoil from below. Dethatch or aerate again if needed.
Poor grass growth
If turf seems to decline or has difficulty emerging through the topsoil layer, it may indicate problems with season timing, preparation, or soil quality. Overseed for fuller growth.
Conclusion
Topdressing over an existing lawn is a process requiring care and the right conditions to succeed. With proper timing in early fall or spring, high quality topsoil free of weeds, thorough lawn preparation, an evenly applied thin layer, and consistent post-application care, adding topsoil can enhance turf health, level grades, and improve soil quality. But inadequate preparation risks grass decline, so the procedure should be undertaken with care. Monitoring the lawn in subsequent weeks and quickly addressing any trouble spots is key to ensure a smooth green lawn emerges through the soil layer.
References
- [1] Pennington. “Topdressing Lawns”. https://www.pennington.com/all-products/fertilizer/resources/topdressing-lawns
- [2] Milorganite. “How to Topdress Your Lawn”. https://www.milorganite.com/lawn-care/lawn-care-how-to/topdress-your-lawn
- [3] This Old House. “How to Top-Dress Your Lawn”. https://www.thisoldhouse.com/lawn-garden/21017458/how-to-top-dress-your-lawn
- [4] Scotts. “How to Topdress a Lawn”. https://www.scotts.com/en-us/library/lawn-basics/how-topdress-lawn
- [5] Extension. “Topdressing Lawns”. https://extension.umn.edu/lawncare/topdressing-lawns
