How to Calculate the Number of TuffBlocks You Need
To estimate TuffBlocks, map the structure’s support beams, then calculate the number of blocks needed along each beam using the maximum spacing allowed by the design and the selected block’s instructions. Add supports required at beam ends, splices, or concentrated loads. The result is a layout estimate, not proof that the blocks, beams, or ground can safely carry the structure.
The calculation starts with a plan, not a guessed spacing. Record the structure’s dimensions, identify where its beams will sit, and confirm the chosen TuffBlock model’s instructions and limits. Then calculate supports for each beam row and check that the ground beneath every block is suitable.
I use the same sequence whether I’m checking a small platform or reviewing a larger layout: establish the requirements, calculate the points, and verify the structure and bearing surface. That helps avoid both missing supports and a count that looks adequate on paper but does not suit the site.
Inspect the Site, Structure, and Bearing Surface
This first check defines what you are supporting and where each support can bear. Record the outside footprint, beam direction and location, design loads, selected TuffBlock model, and local requirements. Also assess the ground at each planned point; block quantity alone cannot confirm a stable foundation.
Record dimensions and the support layout
Measure the structure’s actual outside length and width, using one unit throughout. Then identify the beams and the direction each beam runs. The length supported by a beam is the length used for along-beam spacing; the distance across beam rows is used to set the number of support lines.
Do not assume the structure’s edges and beam lines are identical. Beams may be inset, or the plan may require supports at specific points. Draw the actual beam locations and mark required beam ends, splices, and concentrated loads. A concentrated load is a load focused in one area, such as at a post or other design-specified point.
Confirm block, beam, and ground requirements
Check the current installation instructions for the exact TuffBlock model. Confirm its rated capacity, approved bearing surface, and any placement or installation limits. Do not borrow a capacity or spacing from a different model, an online example, or a project with different loads.
Next, check that the beams can span between the proposed blocks under the project’s loads. A block’s rating does not establish beam capacity, and neither one proves the soil can carry the load. Ground should be firm, prepared as required by the instructions and site conditions, and able to drain without erosion or settlement.
Soft, organic, loose-fill, saturated, or eroding ground needs attention before supports are placed. Frost-susceptible ground may also affect stability, depending on the site and local requirements. Resolve these conditions through an appropriate design or site-specific solution rather than trying to compensate by adding blocks at random.
Calculate TuffBlock Spacing and Install Supports Precisely
Spacing is the greatest permitted distance between support points for the actual design, not a universal number. Determine the maximum along-beam spacing and the maximum spacing between support lines from the beam design, loads, product instructions, and applicable requirements. Then round each interval count up.
Use the formula for a rectangular support grid
For a rectangular grid with equal spacing limits, use:
[ N=\big(\lceil L/S\rceil+1\big)\big(\lceil W/B\rceil+1\big) ]
Here, (N) is the estimated block count, (L) is the supported length, (W) is the supported width, (S) is the maximum permitted spacing along a beam, and (B) is the maximum permitted spacing between support lines. The ceiling marks mean round up to the next whole number.
This formula assumes the layout needs support points at both ends of each measured span. Check the drawing and instructions to confirm that assumption fits your project. If beams are not arranged as a simple rectangular grid, calculate each beam row separately instead.
Calculate block rows separately
For a beam layout, calculate:
Blocks per row = (\lceil L/S\rceil+1)
Multiply that result by the number of beam rows. Then add any separate supports required by the design, such as supports at a splice or beneath a concentrated load. Do not count a required point twice if it already coincides with a calculated support location.
Example: A beam row has a supported length of 12 ft, and the project allows a maximum 6 ft between supports. The number of intervals is (\lceil 12/6\rceil=2), so the row needs 3 support points. With three beam rows, the base count is 9 blocks. Any extra required support points must be added after checking their locations against the plan.
The example shows the arithmetic only. It does not establish that 6 ft spacing, three rows, or any particular block model is suitable for a real structure.
Compare common calculation layouts
| Layout scenario | Calculation | Base count |
|---|---|---|
| One 12 ft beam row, 6 ft maximum spacing | (\lceil12/6\rceil+1) | 3 |
| Three identical 12 ft beam rows, 6 ft maximum spacing | (3 \times (\lceil12/6\rceil+1)) | 9 |
| One 13 ft beam row, 6 ft maximum spacing | (\lceil13/6\rceil+1) | 4 |
| Grid 12 ft by 10 ft, with 6 ft limits along both directions | ((\lceil12/6\rceil+1)(\lceil10/6\rceil+1)) | 9 |
The 13 ft example needs four points because three 6 ft intervals would span 18 ft, while two intervals would span only 12 ft. Round the number of intervals up; never round the support count down to make the layout fit a preferred total.
Mark each point before placing blocks
Use a plan view to mark every support center. Check that the first and last points meet the design’s end-support requirements and that every interval stays within its permitted maximum. Include beam splices, concentrated loads, and other design-required points.
At the site, prepare each bearing location as the product instructions and site conditions require. Place blocks in line under their intended beams, then check alignment, level, and full bearing contact. Follow the specified method for securing or bracing the structure. Confirm permit and inspection requirements before loading or using it.
Verify Deflection, Stability, and Safe Transitions
A correct count does not by itself make a structure safe or stiff. Deflection is the amount a beam bends under load; stability also depends on beam design, support locations, connections, bracing, and bearing conditions. Verify the full load path before use, including how the structure meets adjacent surfaces.
After laying out the blocks, compare actual beam spans with the design limits. Check the selected model’s capacity against the project requirements, and confirm that the ground under each block remains suitable. Do not treat a larger block count as a substitute for checking beam capacity, load placement, or the condition of the bearing surface.
Example scenarios: what the count can and cannot show
These examples illustrate the calculation method, not completed engineering designs.
| Planning situation | Calculation result | What still needs verification |
|---|---|---|
| Three 12 ft beam rows, 6 ft maximum spacing | 3 blocks per row; 9 total before extras | Whether the beam spacing and 6 ft span are permitted for the actual loads |
| Two 13 ft beam rows, 6 ft maximum spacing | 4 blocks per row; 8 total before extras | Beam capacity, end conditions, model limits, and ground bearing |
| A beam splice falls between calculated points | Base count may not change, or may need an added block | Whether the splice requires direct support under the design |
A splice or concentrated load may require a support at a specific location. If that point falls between the regular support points, revise the layout and recalculate the affected spans. If it falls on an existing point, confirm that the design allows the shared support.
A block over weak, saturated, frost-susceptible, or poorly prepared ground can settle even when the count is correct. Independent settlement can distort beams, rack the structure, or damage connected parts. If the site has uncertain soils, changing grades, or signs of prior settlement, get qualified site-specific guidance before proceeding.
Maintain Drainage, Inspect Settlement, and Protect Long-Term Performance
The support plan must remain stable after installation. Check that water does not collect around bearing points or wash away supporting material, and follow the product’s requirements for drainage and ground preparation. Inspect the structure for movement over time, especially after conditions that could affect the site.
Keep a copy of the layout, block model, spacing calculations, and installation instructions with the project records. This makes it easier to confirm what was installed and investigate any later movement. Recheck alignment and level if you notice a change in the structure, a gap at a bearing point, or signs of settlement.
A practical planning example
Suppose a project has three beam rows, each with a supported length of 15 ft. The design and product instructions establish a maximum 5 ft spacing along each beam. Each row then needs (\lceil15/5\rceil+1=4) supports, for a base total of 12.
Before ordering, the plan still needs to confirm support-line locations, any required points at splices or concentrated loads, the selected block model’s limits, and ground conditions. If one beam row has an extra required support, update the count and check the revised spans rather than simply adding a block without reviewing the layout.
Next step: finalize the drawing and count only after the beam design, block instructions, and bearing conditions agree. If they do not, resolve the conflict before installation.
Frequently Asked Questions
These answers clarify the count method and its limits. Use them as a planning check, then verify the final layout against the exact product instructions, project design, and local requirements. A formula can organize support points, but it cannot approve a structure or establish soil capacity.
How do I calculate the number of TuffBlocks for a beam row?
Divide the supported beam length by the maximum permitted spacing, round up to a whole number of intervals, then add one. For example, a 13 ft row with a 6 ft spacing limit needs (\lceil13/6\rceil+1=4) support points.
Is there a standard spacing for TuffBlocks?
There is no single spacing that is safe for every structure. Spacing depends on the exact block model, beam capacity, loads, support layout, ground, and applicable requirements. Use the project design and current manufacturer instructions.
Should I round spacing up or down?
Round the number of spacing intervals up. Rounding down can leave a span longer than the permitted maximum. After calculating, check the actual distance between every adjacent support point.
Do I count block rows or individual blocks?
For a beam layout, calculate blocks per row, then multiply by the number of beam rows. Add separately required points that are not already included. For a regular grid, use the two-direction formula and verify that it matches the actual layout.
Do I need a block at every beam splice?
Follow the project design and applicable instructions. A splice may need support at or near its location. If a required support falls between regular points, revise the layout and check the resulting beam spans.
Can I use this method for a shed or deck?
The arithmetic can help plan support points for either, but it does not establish that a particular spacing or block model is suitable. Confirm the structure’s loads, beam design, product instructions, ground conditions, and local permit requirements.
Does adding more blocks make the structure safe?
Not necessarily. More blocks do not correct an undersized beam, unsuitable ground, poor connections, or missing bracing. Each support must be placed where the design requires it and bear on a suitable, prepared surface.
What if the ground is soft or waterlogged?
Do not place blocks on unstable or waterlogged ground. Address the bearing condition and drainage using a site-appropriate solution that meets product and local requirements. Seek qualified guidance if soil stability or settlement risk is uncertain.
Should I include extra blocks in my order?
First finalize the support plan, including required points at splices and concentrated loads. If you choose to keep spare blocks, treat them as replacements, not as a substitute for a designed support location or an approved layout.
(This article was written by one of our staff writers, Thomas Whitaker. Visit our Meet the Team page.)