TuffBlock Calculator – How Many TuffBlocks Do You Need?
Instantly calculate deck area, deck block spacing, and how many TuffBlocks you need for your floating deck or shed foundation.
Enter your deck length and width in feet to estimate required TuffBlocks and recommended pack quantities.
✔ Calculated on 16" on-center spacing & ground level decks
✔ 150,000+ real builds
Or use our deck block spacing chart below to estimate how many TuffBlocks you need based on common deck sizes.
| Deck Length (feet) | Deck Width (feet) | Deck Area Calculator (sq feet) | Estimated TuffBlocks |
|---|---|---|---|
| 8 | 12 | 96 | 24 |
| 20 | 10 | 200 | 42 |
| 20 | 12 | 240 | 42 |
| 30 | 10 | 300 | 60 |
| 20 | 16 | 320 | 56 |
| 35 | 10 | 350 | 72 |
How TuffBlock Spacing Affects Your Deck Build
The TuffBlock calculator estimates block quantity based on standard residential deck construction - typically 16-inch on-center joist spacing for ground-level floating decks.
“On-center” spacing refers to the distance from the center of one joist to the center of the next. Sixteen-inch centers are common because they provide reliable structural support while keeping material use efficient. Your required number of TuffBlocks will increase or decrease depending on joist spacing and beam layout.
TuffBlocks should be evenly distributed beneath joists and beams to ensure consistent load support. As a general guideline, support rows should not exceed 60 inches (center to center) unless your structural design specifies otherwise.
The calculator provides a strong geometric estimate, but final spacing should always comply with local building codes and project-specific requirements.
Ground-Level Deck Assumptions
This calculator assumes a freestanding, ground-level floating deck that does not require deep concrete footings. TuffBlocks are designed as an above-ground alternative to traditional concrete deck blocks and pier footings, making them well suited for:
- Low-profile decks
- Freestanding backyard platforms
- Shed foundations
- Garden walkways
Because floating decks distribute loads differently than elevated decks, spacing and layout directly affect how many blocks are needed.
Joist Span & Support Basics
Joist span, lumber size, and load requirements all influence block quantity. Longer spans may require additional support points to reduce deflection. You may need extra TuffBlocks if:
- Lumber size
- Live loads are heavier than standard residential use
- The deck includes stairs or multiple tiers
- The layout is irregular
Limited cantilevering is possible. For deck extensions beyond the final support row, we recommend placing TuffBlocks no more than 12 inches from the end of the build to maintain structural stability.
ICC Certified Deck Foundation System
150K+ Real Builds
Rated 4.9/5 stars by DIYers & contractors
25 year warranty guarantee
Trusted for Decks, Sheds & Floating Foundations
Related Resources for Your Deck Build
Learn how to calculate deck block spacing, compare TuffBlocks to concrete, and install your floating deck correctly.
How many deck Blocks do I need?
A detailed guide explaining deck block spacing, joist layout, and how to estimate the right number of TuffBlocks for your project.
Read More
TuffBlock vs Concrete Deck Blocks
Compare TuffBlocks with traditional concrete deck blocks and pier footings to see which foundation system is right for your build.
Read More
How to Install TuffBlocks
Step-by-step instructions for placing, spacing, and leveling TuffBlocks for a strong, ground-level deck foundation.
Read MoreHow many deck Blocks do I need?
A detailed guide explaining deck block spacing, joist layout, and how to estimate the right number of TuffBlocks for your project.
Read More
TuffBlock vs Concrete Deck Blocks
Compare TuffBlocks with traditional concrete deck blocks and pier footings to see which foundation system is right for your build.
Read More
How to Install TuffBlocks Step-by Step guide
Get detailed instructions for placing, spacing, and leveling TuffBlocks for a strong, ground-level deck foundation.
Read MoreYou can also check out our Installation Guide.
Frequently Asked Questions
Instantly calculate deck area, block spacing, and how many TuffBlocks you need for your build.
Engineered smart. Built tougher.
Contractor & DIY Review
Site Built Sheds (Charlotte, NC)
Jerry from Site Built Sheds uses TuffBlocks on every job because they’re faster, lighter, and more reliable than concrete.
Justin & Jess DIY (Nashville, Tennessee)
“As a first-time DIYer, TuffBlocks were a game-changer. They made the whole deck project simple and straightforward.”
Built for the Jobsite
Forget hauling heavy blocks or waiting days for concrete to cure.
With TuffBlock, you can:
Cut install times in half — crews can frame the same day.
Keep overhead low — reduce transport costs and back-breaking labor.
Work anywhere — on uneven soil, turf, or pavers with a little leveling.
Deliver lasting builds — backed by a rock-solid 25-year warranty.
- Cut install times in half — crews can frame the same day.
- Keep overhead low — reduce transport costs and back-breaking labor.
- Work anywhere — on uneven soil, turf, or pavers with a little leveling.
- Deliver lasting builds — backed by a rock-solid 25-year warranty.
What others say
How to Build Easy With TuffBlocks
Drop
Place your TuffBlocks directly onto firm, level ground — grass, dirt, gravel, or even concrete. No need to dig holes or pour footings. Just space them where your posts or joists will go.
Level
Use a spirit level to make minor ground adjustments if needed. TuffBlocks work best on flat, stable surfaces — and minimal prep is all it takes. Tip: Use packers such as crusher dust underneath for extra stability and longevity.
Build
Drop in your 3.5" or 4" posts or 1½" - 2" Joists & Bearers — From here, just start building your deck, shed base, stairs, or even tiny home floor.
