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TuffBlock deck blocks
TuffBlock is a heavy duty deck block for freestanding decks, sheds, walkways and pergolas. Set the blocks out, level them, and frame straight off the top. There is no digging, no concrete and no cure time, so a full foundation goes down in an afternoon. Each block spreads the frame load across nearly a full square foot of bearing, using the floating foundation method.
- Fits nominal 2-by joists and 4x4 posts
- Easily build level frames on sloping ground
- Allows ultra low decks without excavating
- Break tested to 11,000 lbs each
- UV stabilized for extreme direct sun
- Made in the USA
Not sure how many? Use the deck calculator.
A footing works by spreading load over enough ground area that the soil beneath it stays within its bearing capacity. Bearing pressure is load divided by area, so the governing dimension is footprint. TuffBlock presents an 11.81 inch square base, larger than a standard concrete deck block, and the rib structure beneath transfers load across that full area.
On a freestanding deck the frame rests on the block rather than being fixed to it, so the mass of the block itself carries no structural function.
The block also separates the timber from the soil. Ground moisture stops at the block instead of wicking into the joist, and the ventilated underside maintains airflow beneath the frame. Sustained moisture is the primary cause of both rot and termite activity in ground-contact timber.
Because nothing is placed below grade, no site investigation for buried services is required before installation.
- Footprint
- 11.81" x 11.81"
- Height
- 3 9/16" total, 2" to joist
- Weight
- 1.5 lbs
- Fits
- Nominal 2-by joists, 4x4 posts
- Rated load
- 1,700 lbs per block
- Peak load
- 9,230 lbs per block*
- Break tested
- 11,000 lbs per block
- Material
- UV-stabilized recycled polypropylene
- Warranty
- 25 years
* Independently tested by MechTest, ISO/IEC 17025 accredited, report RB26-15664-01.
Independent test results and technical documents. Download and hand them to your building department or engineer.
Block count is set by your lumber, not by the block. Each TuffBlock carries far more than any vertical load a deck puts on it, so what matters is joist size, joist spacing and how far the lumber can span without bowing or bounce. TuffBlocks sit at the same spacing as an in-ground pier or concrete deck block, so standard span tables apply. Open the deck block calculator.
Most local codes are built on the IRC. Freestanding decks on pier blocks under 200 sq ft with a walking surface under 20" above grade don't require footings. Independently tested to ICC-ES AC49. Always confirm with your local building department.
Free shipping on every order. At 1.5 lbs a block, your whole foundation arrives by courier. 30 day returns on unopened packs.
Same job. Different trade-offs.
Same job. Different trade-offs.
TuffBlock
Concrete block
Independent lab testing loaded both to destruction. TuffBlock averaged 9,230 lbs peak. No-brand adjustable blocks averaged 463 lbs, and failed suddenly when the threads stripped.
Manufactured in Arkansas. Supporting American jobs.
UV stabilized recycled polypropylene, lab tested for heat, cold and sun.
Every part earns its place
See TuffBlock in action
What builders are saying
How many blocks do you need?
Enter your deck dimensions and lumber. We'll tell you the block count and the pack size.
Your lumber and layout decide how many blocks you need, not the block itself.
Based on 16" on-centre joist spacing and the max span for your selected joist size, with end blocks set 12" in from each joist end — a standard single-run layout. Sistered joists, bearers, cantilevered edges and sloped sites will change your count. Always confirm against your local building code.
Your lumber sets the spacing, not the block
Each TuffBlock is a single vertical support point, the same job a concrete pier does. At 1,700 lbs rated, the block is rarely the limit. What sets your block count is the lumber on top of it.
Deck boards set your joists on center. Too far apart and the boards bounce underfoot. Closer joists on center means firmer boards. Wood decking usually runs 16" on center, composite 12" on center. Check your decking manufacturer.
Joists set your block spacing. Blocks too far apart along a joist and the joist bounces. Either space the blocks closer, or use thicker joists that can span further. Your local span tables set the limit.
Beams cut the count. On a raised deck, a row of beams under the joists carries them, so only the beams need blocks. That typically cuts the count by 40 to 60%.
Deck shape matters too. On a rectangular deck, running joists along the long side usually needs fewer blocks.
If you're between two layouts, go with more support. It's the difference between a deck that feels solid and one that doesn't.
Specifications
- Footprint
- 11.81" x 11.81" (300 mm)
- Height
- 3 9/16" total (90 mm)
- Height to joist bearing
- 2" (50 mm)
- Weight
- 1.5 lbs
- Material
- UV-stabilized recycled polypropylene
- Rated load
- 1,700 lbs per block
- Peak load
- 9,230 lbs average, independently tested
- Break tested
- 11,000 lbs per block
- Temperature range
- -20F to 125F
- Joist slot 1
- Up to 1 5/8" (41 mm)
- Joist slot 2
- Up to 1 7/8" (47 mm)
- Post seat
- 3 1/2" or 4" (90 or 100 mm)
- Minimum soil bearing
- 1,500 psf
- Maximum build height
- 48" above grade
- Warranty
- 25 years
Questions builders ask
UV-stabilized recycled polypropylene, independently lab tested to ICC-ES AC49, the acceptance criteria for molded plastic footing pads. That testing covered UV resistance, temperature effects, soil exposure and freeze/thaw resistance, and the block is rated from -20F to 125F. 150,000 builds to date with zero failures.
Rated at 1,700 lbs per block, with a 5.4x safety factor. Independent testing recorded an average peak load of 9,230 lbs, and our own destructive testing runs past peak to complete failure at 11,000 lbs. On a freestanding deck the frame sits on top of the block, so what carries the load is the 11.81 inch square bearing footprint, not the weight of the block.
Most local codes are built on the IRC. Freestanding sheds up to 600 sq ft of light frame construction don't require frost protection. Free-standing decks on pier blocks don't require footings at all where the deck is under 200 sq ft and the walking surface stays under 20 inches above grade. Some states run their own code, Wisconsin among them, so always confirm with your local building department.
TuffBlock is designed for vertical load. Uplift and lateral loads need to be resisted separately, and earth anchors at perimeter points are the usual answer.
Bearing pressure is load divided by area, and the 11.81 inch square base spreads load across roughly a square foot of ground. Strip loose topsoil back to firm ground and compact it before placing the blocks. The block needs soil with a bearing value of at least 1,500 psf, which covers most sand, gravel and clay.
Yes. The slab is already doing the footing's job, so the blocks keep timber off the concrete, give you a drainage gap, and take up any fall in the surface.
Level each block, not the site. Always build on grade: cut the high side back to firm ground so each block sits on a level surface. Never build up under a block with soil or aggregate. For real fall, use 4x4 posts in the pocket and vary the post lengths. A 10 foot run with a foot of drop is normal, and most people don't realise until they pull a string line.
Your lumber decides, not the block. Each TuffBlock carries far more than any vertical load a deck puts on it, so the count comes down to joist size, joist spacing and how far the lumber can span without bowing or bounce. TuffBlocks sit at the same spacing as an in-ground pier or concrete deck block, so standard span tables apply. Use the deck block calculator above to work it out from your dimensions and lumber.
Technical documents
Independent test reports and installation documents for your building department, engineer or inspector.
Ready to build on better?
No digging, no concrete, no cure time. Set the blocks, frame on top, done in an afternoon.