Four WSDOT fine aggregate gradings, and the sieve that separates them
Ask for sand and you will be asked which sand. That is not a sales technique. WSDOT grades fine aggregate separately for concrete, for mortar, for a drainage blanket and for sand drains, and they differ most on the No. 200 sieve, the fines. Masonry sand permits nearly twice the fines of concrete sand, and fines are what decide whether a bedding layer drains or holds water and washes away.
Sand volume, and what the use requires
ft
ft
ft
in
%
cu ft
lb/cu ft
Weight is only calculated if you supply a density. Damp sand bulks up considerably, so ask whether a quoted figure is dry or as delivered.
Specification summary
Generated from on .
Reopen that address to reproduce these figures exactly.
Entered
Result
Two sands, plotted
Worked example
A 20 ft by 16 ft paver patio bedded at 1 in, with a 10% allowance, bought in bulk.
Area. 20 × 16 = 320 sq ft.
Volume. 320 × 1/12 = 26.67 cu ft = 0.99 cu yd.
With waste.1.09 cu yd.
Weight. Not calculated. Ask the yard, and ask whether the figure is dry or as delivered.
What the use wants. A coarse, well graded sand with the No. 200 held to 3.0% maximum.
What it must not be. Masonry sand, which permits 5%.
Notice how little sand a bedding layer actually is: one inch over a decent-sized patio is about a cubic yard, which is a fraction of the base course underneath it. That is the right proportion. If your bedding sand order is approaching the size of your base order, the bedding layer is too deep, and a thick bedding layer rolls under load and takes the pavers with it.
The formula
Volume is trivial. The specification is the page:
V = A × d/12 order = V(1 + k)
A, d
area in sq ft and layer depth in in
k
waste allowance. Ours
27
cubic feet in a cubic yard
No. 200
the sieve that separates the gradings. Fines, and therefore drainage
There is no compaction term here. A bedding layer is screeded and the pavers are vibrated into it, which is not the same as compacting the sand, and a bedding layer thick enough to need a compaction allowance is too thick.
One word, four specifications
Sand is the most ordinary material on a site and the one most likely to be bought wrong, because the word covers materials that a specification treats as entirely different.
WSDOT grades fine aggregate for surface finishing and for masonry mortar with two separate tables, and grades a sand drainage blanket and sand drain backfill with two more. The four differ throughout, and they differ most at the No. 200 sieve, which is the silt-sized fraction.
Mortar sand is finer at every sieve and permits up to 5% passing the No. 200 against 3% for concrete sand. The drainage gradings hold it to 3.0%. Those are not rounding differences, they are the difference between a material that drains and one that does not.
None of which appears on a bag or a delivery note. What does exist is a sieve analysis, because any supplier selling to a specification has to produce one, and asking for it is the whole of the quality control available to a person buying a yard of sand.
Two fine-aggregate gradings from one specification
Sieve
Surface finishing, % passing
Masonry mortar, % passing
No. 4
99 to 100
99 to 100
No. 8
90 to 100
95 to 100
No. 16
60 to 90
70 to 100
No. 30
35 to 70
40 to 75
No. 50
10 to 30
10 to 35
No. 100
0 to 5
2 to 15
No. 200
0 to 3
0 to 5
Read 2026-09-08. Natural sand columns from WSDOT 9-03.2(1) and 9-03.2(2), percent passing by weight.
Sand is four different materials, and the difference is the fines
Ask for sand and you will be asked which sand, and the question is not a sales technique. WSDOT grades fine aggregate separately for at least four purposes, and they are genuinely different specifications:
Natural sand, percent passing by weight, WSDOT 9-03.2
Sieve
Surface finishing, % passing
Masonry mortar, % passing
No. 4
99 to 100
99 to 100
No. 8
90 to 100
95 to 100
No. 16
60 to 90
70 to 100
No. 30
35 to 70
40 to 75
No. 50
10 to 30
10 to 35
No. 100
0 to 5
2 to 15
No. 200
0 to 3
0 to 5
Read down the two columns. Masonry sand is finer at every sieve: at the No. 16 it must pass 70 to 100 against 60 to 90, and at the No. 100 it must pass at least 2 where concrete sand may pass none.
And at the No. 200 it permits nearly twice the fines. 5% maximum against 3%. The No. 200 sieve is silt-sized material, and it is the sieve that decides whether water moves through the sand or sits in it.
The drainage gradings go the other way and are stricter again:
Specification
Max passing No. 200
What it is for
Sand drainage blanket (9-03.13(1))
0-3.0%
Drainage. Wide grading, and the fines held to 3.0% maximum.
Backfill for sand drains (9-03.13)
0-3.0%
Drainage. Tighter still, and again 3.0% fines maximum.
So a material sold as sand can legitimately be any of these, and the one you want under pavers is the one that drains rather than the one that spreads nicely.
Bedding depth, and why an inch is the answer
A paver bedding layer is thin on purpose. Its job is to let the pavers seat evenly, not to make up level.
Thick bedding sand rolls. Under a wheel load a deep loose layer moves sideways, and the pavers above it move with it. The result is ruts in the wheel tracks and a lipped edge where the load stopped.
Level belongs in the compacted base underneath, where it is a structural layer that has been compacted in lifts and will stay where it is put. Using bedding sand to correct a base that was not screeded flat is the commonest reason a patio fails in its first year.
Which is also why the bedding order is small. On a 320 sq ft patio it is about a cubic yard, against several yards of base. If those two numbers are getting close, the layer is too deep.
Damp sand bulks, and it bulks a lot
Sand delivered damp occupies noticeably more volume than the same sand dry, because a film of water around each grain holds the grains apart. The effect peaks at a few per cent moisture and can add something like a fifth to the apparent volume.
That matters twice. A cubic yard of damp sand contains less sand than a cubic yard of dry sand, and a weight quoted dry will not match a load delivered wet.
So ask which one a quoted density is. It is the same question as on the gravel page and it has the same answer: the yard weighs material daily and knows, and a web page does not.
The effect reverses as it dries, which is why a heap left on a drive settles noticeably over a week without anybody touching it.
What this page does not cover
Polymeric jointing sand. That is a different product with its own coverage figures, published by its manufacturer per joint width and paver thickness, and it goes in the joints rather than under the pavers.
The base course. A different material at a different depth with a compaction allowance. The gravel calculator handles it.
Bedding for anything structural. Pipe bedding and equipment pads have their own specifications and are not a landscaping decision.
Whether your base is flat enough. No quantity of bedding sand fixes a base that is out, and trying is what causes the failure this page describes.
Why the wrong sand makes a patio sink
A paver bedding layer has two jobs: give the pavers something to seat into, and let water through to the base below. Both depend on the fines.
Fines hold water. Silt-sized particles fill the spaces between the sand grains, so water that gets through the joints stops at the bedding layer instead of draining into the base. In a freeze it lifts.
Fines migrate. Water moving through a bedding layer carries the finest fraction with it, and where it goes the layer loses volume. That is what a rut in a paver drive actually is: not the pavers sinking, the bedding sand leaving.
Which is why masonry sand, the finer specification with nearly twice the permitted fines, is the wrong material for bedding even though it is the pleasanter one to screed. It is specified for mortar, where it is bound into cement and going nowhere.
Play sand is a different problem again. It is washed and uniformly rounded, which makes it kind to hands and useless as bedding, because rounded uniform grains do not interlock and the layer stays mobile.
The words on the bag are marketing. The sieve analysis is the specification, and any supplier selling to a spec can produce one.
The source, and what it does not cover
Read 2026-09-08. 2027 Standard Specifications M 41-10, Division 9 Materials, Washington State Department of Transportation, section 9-13.1(2). Sizes riprap by weight and volume together, which is the only place found that pins a stone's weight to its volume in a government publication. Both equivalences give about 149 lb per cubic foot, which is SOLID rock rather than a loose pile.
That document sets minimum properties for engineered aggregates: gradation, degradation factor, Los Angeles wear, specific gravity. What it does not contain, and what no government publication found from here contains, is a table of typical loose densities for the materials sold at a landscape yard. The specifications describe what a product must achieve, not what a heap of it weighs.
Which is the honest answer to why every gravel calculator's tonnage figure is uncited. There is nothing to cite.
Frequently asked questions
How much sand do I need for a paver patio?
At a 1 in bedding layer, about a cubic yard per 320 square feet. A 20 by 16 ft patio is 0.99 cubic yards, or 1.09 with a 10% allowance. That is small compared with the base course underneath, and it should be: bedding is for seating the pavers, not for making up level.
What kind of sand goes under pavers?
A coarse, well graded sand with low fines. WSDOT's drainage gradings hold the No. 200 sieve to 3.0% maximum. Masonry sand permits up to 5% and is finer at every sieve, which makes it pleasant to screed and wrong for bedding, because the fines hold water and migrate.
Can I use play sand under pavers?
No. Play sand is washed and uniformly rounded, which is what makes it comfortable to handle and useless as bedding: rounded uniform grains do not interlock, so the layer stays mobile under load. Bedding sand needs angular, well graded particles that lock together.
What is the difference between mason sand and concrete sand?
The grading. Mason sand is finer at every sieve and permits nearly twice the fines: up to 5% passing the No. 200 against 3% for the surface finishing grading. Mason sand is specified for mortar, where it is bound into cement and cannot migrate.
How deep should paver bedding sand be?
About an inch. Deeper layers roll under load and take the pavers with them, which shows up as ruts in the wheel tracks. Level belongs in the compacted base underneath, not in the bedding layer.
How much does a yard of sand weigh?
It depends on the gradation and the moisture, and this page will not guess. Damp sand bulks up considerably, so a cubic yard of damp sand contains less sand than a cubic yard of dry, and a density quoted dry will not match a load delivered wet. Ask your supplier which one their figure is.
How do I know I am getting the right sand?
Ask for the sieve analysis. Any supplier selling to a specification has to produce one, and it is the only quality control available to somebody buying a yard of sand. The name on the bag is marketing; the gradation is the specification.
Check these numbers yourself
2027 Standard Specifications M 41-10, sections 9-03.2 and 9-03.13Washington State Department of Transportation. Grades fine aggregate separately for surface finishing, masonry mortar, a sand drainage blanket and sand drain backfill. The four differ most on the No. 200 sieve, which is the fines.
How every figure here is verified: Sources & Method. Who builds this: About. Found something wrong? Tell us and it gets fixed or removed.
Figures on this page last checked against the source documents on 2026-09-08. Codes are amended locally; confirm against the edition your jurisdiction enforces.
The gradings quoted are WSDOT's, read 8 September 2026, and are one state's specifications. Other agencies and ASTM grade fine aggregate differently, and the material your supplier sells may meet none of them. Weight is not calculated without a density you supply, because sand density moves with gradation and moisture. Polymeric jointing sand, base course and structural bedding are not covered here.