An AutoCAD hatch pattern library: 12 construction materials

You are drawing a wall section and need the concrete symbol. The hatch palette opens with close to a hundred patterns and not one of them matches the Vietnamese standard. You download an AutoCAD hatch pattern library, follow the instructions, and the Custom list is still empty.

This article publishes the Institute's set of 12 patterns, every one hatched for real on AutoCAD 2027, and names the trap that stops most downloaded sets from appearing at all. For the whole discipline of presenting a drawing, the Institute runs an AutoCAD course for construction.

Nearly a hundred patterns ship with the software, and still not enough

Counted directly in the pattern files of the 2027 release on the machine:

Eighty-three sounds ample, but they follow the ANSI and ISO symbol sets. The Vietnamese standard symbol for concrete, for timber flooring, for rubble stone — none of them is there. Which is why anyone who has produced drawing sets for a few years carries a private hatch collection.

The Institute's set: 12 patterns, downloadable

The set covers the twelve material symbols that come up most often on construction drawings. Each one was loaded into AutoCAD 2027 and hatched onto a real square; none of them exists only on paper.

Every definition is in millimetres, which suits a drawing in mm units. At 1:100 a Scale of 1 reads correctly.

There is a second reason to keep an AutoCAD hatch pattern library of your own rather than rely on whatever ships with the software. A drawing set is read by contractors, checkers and clients who have seen thousands of drawings, and they read symbols faster than they read notes. A concrete symbol that matches what they expect saves a phone call; one that does not costs an RFI. The twelve below were chosen by how often they come up on Vietnamese construction drawings, not by how interesting they are to draw.

Loading a hatch pattern: three steps with the dialogs

Loading a hatch pattern takes three steps. The screenshots below come straight from AutoCAD 2027, so follow them in order.

Step 1 — unzip somewhere permanent.

Unzip the archive into a folder that will stay put, say D:\CAD\hatch-iic. Permanent matters: AutoCAD remembers the path and copies nothing, so deleting or renaming the folder takes the patterns out of the list again.

Step 2 — register that folder on the support path.

Type OP and press Enter to open Options. Go to the Files tab, click the plus beside Support File Search Path to expand it, click Add… then Browse…, and point at the folder you just unzipped. The new path appears at the bottom of the list, as below. Click OK.

Step 3 — pick the pattern on the Custom tab.

Type H and press Enter. Set Type to Custom, then click the … button beside the Custom pattern box. The Hatch Pattern Palette opens; switch to the Custom tab and all 12 patterns are there, with a preview on the right for whichever name you click.

Two things trip people up at step three. The Custom pattern box just above the … button lists only patterns used recently, so the first time it is empty — that is not a failed install, just click the … button. And if the Custom tab itself is empty, the path from step two has not taken; go back and check it.

Once the names are familiar there is a shortcut: leave Type on Custom and type the pattern name straight into the Pattern box.

The trap that stops most downloaded sets working

This is the part worth the reading time, and the reason you can download five hatch sets and see none of them.

The test: put all 12 patterns into one file called iic.pat, register its folder on the support path, and try to hatch each one. Then split the same 12 definitions into 12 separate files, each named after its pattern, and repeat exactly the same test.

Not a syntax problem, since the definition lines are identical. Only the packaging differs, and nothing on screen explains why.

Autodesk's documentation says precisely this, on a customisation page few people read. The custom PAT file page states: "Each custom hatch pattern is stored in a separate PAT file that has the same name as the custom hatch pattern. For example, the custom hatch pattern "WATER" must be stored in a PAT file named water.pat."

So custom hatch patterns work in exactly two arrangements:

The Institute's set is packaged the first way: the archive holds 12 ready-split .pat files. Download, unzip, and it works with nothing to edit.

A concrete hatch and the structural group

The first four patterns are the structural section group, and the most searched for.

A concrete hatch is IIC-BT: sparse dots on two axes at 160 spacing, the symbol for unreinforced concrete — blinding, lean mix, plain blockwork.

IIC-BTCT is reinforced concrete: cross hatching at 120 spacing. This is the one that appears most on structural drawings, for beams, columns, slabs and foundations.

IIC-VUA is render, dense dots at 60, for the thin plaster layer in a wall section. IIC-GACH is brickwork in running bond at 120.

Organising sections and symbols with a proper layer set is covered in our article on layers in AutoCAD.

A timber floor hatch and the finishes group

The second group belongs on architectural plans and elevations.

A timber floor hatch comes in two kinds that people routinely confuse. IIC-GO is floorboards seen from above, laid in running bond. IIC-XUONGCA is herringbone parquet, two sets of 45° dashes interlocking — the pattern on better timber floors.

IIC-GOVAN is different from both: it draws the grain, not the boards, for a section through a timber member or the elevation of a fitted unit.

The rest of the group is IIC-GACHLAT for 300 floor tiles, IIC-KINH for glass and IIC-DA for rubble stone. The last two, IIC-CAT and IIC-DAT, belong on foundation sections.

Scale decides whether a pattern reads or turns solid

A downloaded pattern that hatches as a solid black mass, or as an empty white box, is almost always a scale problem rather than a broken file.

Those figures follow from the definitions being metric. A dash spaced 120 units apart is 120 mm on the model, which prints as 1.2 mm at 1:100 — about right for a hatch that reads without filling in. Halve the drawing scale and you halve the hatch Scale to keep the same printed density.

The rule to remember: the larger the printed drawing, the smaller the Scale. Scale and pattern origin are covered in detail in our article on the hatch command in AutoCAD. The matching linetype set is in our article on an AutoCAD linetype library.

Three things often repeated that are not true

Frequently asked questions

How do I install an AutoCAD hatch pattern library properly?

Unzip it somewhere permanent, register that folder under Options → Files → Support File Search Path, then pick the pattern with Type set to Custom.

I downloaded a hatch library and the Custom list is still empty.

Almost certainly the whole set sits in one .pat file. Split each pattern into its own file, named after the pattern, and register the folder again.

Where do I register the folder?

Type OP, open the Files tab, expand Support File Search Path, click Add then Browse to the folder holding the .pat files.

The hatch comes out as a solid black mass.

Raise the Scale. Solid means the pattern lines are now closer together than the printed line width.

How many patterns are in this set, and in what units?

Twelve, defined in millimetres. A drawing at 1:100 uses Scale 1.

Can I add my own patterns to the set?

Yes. Drop another .pat file into the same folder, remembering that the file name must match the pattern name after the asterisk.

Should I append the patterns to acadiso.pat instead?

You can, and they then appear under Predefined rather than Custom. The cost is that a reinstall or an upgrade replaces that file and takes your patterns with it.

Does the person I send the drawing to need this set installed?

No. The hatch is already in the drawing and displays correctly. They only need the set if they want to hatch new areas with the same pattern.