An ACM rainscreen system hangs aluminum composite panels in front of a drained, ventilated space, and the biggest choice is how the joints between panels are closed. In a wet-seal system, every joint gets backer rod and sealant, so the panel face is the main weather line. In a dry-joint system, the joints stay open or gasketed, and the air and water barrier behind the panels does that job.
This guide compares the two for owners, architects, general contractors and panel installers. For what ACM is made of, core choices and fire-code questions, see our aluminum composite panels page. Architectural Metal Panels routes and folds ACM trays in our New Brunswick, NJ shop to approved shop drawings, and your installer hangs them.
What is the difference between wet-seal and dry-joint ACM?
Wet-seal closes every reveal with sealant; dry-joint leaves the reveals open or fitted with gaskets or extrusions and manages water behind the panels. Strictly speaking, wet-seal is a face-sealed barrier wall with a backup barrier, while dry-joint is a true rainscreen.
| Factor | Wet-seal | Dry-joint |
|---|---|---|
| Joint | Backer rod and sealant in every reveal | Open reveal, gasket or extrusion, with no field sealant |
| Main weather line | Panel face and sealant, with a barrier behind as backup | Air and water barrier behind the panels |
| Look | A sealant line in each reveal, usually color-matched | A crisp shadow line at each reveal |
| Movement | Taken up by the sealant, which must stretch | Taken up by clips and extrusions; the joint stays open |
| Upkeep | Joints need inspection and, in time, new sealant | Little joint upkeep, but hidden flashings must be right first time |
| Barrier behind | Standard water-resistive barrier | A barrier its maker accepts behind open joints |
| Typical fit | Sign bands, fascias, column covers, canopy edges | Taller elevations, entrances, hard-to-reach walls |
Both start the same way in the shop. Each panel is routed on the back on our 24-by-7-foot CNC router table and folded into a tray, a method called route-and-return, which gives it stiff returned edges. The returns are formed for the clips or extrusions of the chosen system, so settle the joint system before fabrication starts.
How does a wet-seal ACM system work?
The installer hangs the trays on clips or angles fixed to the wall and fills the reveals between them with backer rod and sealant. The sealed face sheds the rain, and any water that gets past a joint should be stopped by the barrier behind.
The sealant does the hard work, so the joint design matters. The reveal has to be wide enough for the sealant to stretch as each panel grows and shrinks with temperature. The sealant must suit the panel finish, go on with the primer its maker calls for and be tooled to the right depth.
Wet-seal suits small, reachable areas: sign bands, fascias, column covers, canopy edges and storefront surrounds. It also suits re-cladding work where the wall depth is tight.
How does a dry-joint rainscreen work?
Panels hang on a subframe or extrusion system with open or gasketed reveals, leaving a space behind them that drains and ventilates. Most rain hits the panel face and runs off. The small amount that enters a joint drains down the cavity and out at the base.
Because the joints are open, the wall behind them carries the real weather protection. A dry-joint wall needs:
- A continuous air and water barrier, lapped and sealed at every opening
- A barrier product its maker accepts behind open joints, where it sees daylight and weather
- Flashings at window heads, floor lines and the base that throw water back out
- A clear drainage path at the bottom, screened against insects
- A subframe set flat enough that the reveals stay straight
Dry-joint suits taller elevations, entrances where a sharp reveal is part of the design, and buildings where future sealant work would be hard to reach.
Which system handles New Jersey weather better?
Either ACM rainscreen system handles it when detailed well. The difference is where the risk sits: on a wet-seal wall it sits in the sealant you can see, and on a dry-joint wall it sits in the barrier and flashings behind the panels.
Wind drives rain into joints on exposed elevations, and winter brings repeated freezing and thawing. Sun on south and west walls ages sealant fastest, so wet-seal joints there need the closest watch. On a dry-joint wall, the same sun reaches the barrier through the open reveals, which is why the barrier has to be one its maker accepts for that exposure.
Clip and subframe spacing are designed for the wind at the site. New Jersey guidance in DCA Bulletin 19-1 tells designers to take wind values from ASCE 7-based tools for the exact address. Near the ocean or a bay, salt air adds its own checks; our guide to metal near salt water explains them.
How much upkeep does each system need?
Wet-seal needs more routine upkeep; dry-joint needs more care up front. Over the life of the wall, the owner takes on one or the other.
On a wet-seal wall, plan on regular joint inspections and on replacing sealant as it fails. That is easy at a one-story fascia and much harder on an upper floor that needs a lift. On a dry-joint wall, the joints need little attention, but a missed flashing or a torn barrier means taking panels off to reach it. On both, rinse the panel faces now and then and keep the drainage path at the base clear.
How do the joints meet windows, coping and the base?
The edges of the panel field are where both systems succeed or fail. Every head, jamb, sill, corner and wall top needs a detail that laps the right way.
- Windows and storefronts. The window system and the panel barrier must lap correctly at every head, jamb and sill, with head flashings that throw water clear of the panel below.
- The top of the wall. At the roof edge, the panels meet metal coping, which has to lap over the panel and shed water outward.
- The base. Panels stop above grade with a drip and clearance, and on a dry-joint wall the cavity needs a screened opening to drain.
- Corners, soffits and returns. Folded corner trays keep the reveal line going around the building, and transitions to other materials take custom trim formed in the panel color.
Does the joint system change fire-code requirements?
Not on its own. Fire rules look at the panel core and the whole wall assembly, including insulation and barrier, so the architect sets the requirement and our aluminum composite panels page explains the core options.
How do you choose between wet-seal and dry-joint?
Choose an ACM rainscreen system by design intent, building height and the tested wall assembly first, then by the upkeep the owner can support.
- Pick dry-joint when the design wants a crisp reveal, the elevation is tall or hard to reach, or the owner wants to avoid future sealant work.
- Pick wet-seal for small, reachable areas such as sign bands, fascias, column covers and canopy edges, or where wall depth is limited.
- Mix them with care. One building can use both, as long as the line where the systems meet has its own flashing detail on the drawings.
- Check the existing wall. On a re-clad, the old wall has to be sound enough to anchor a subframe, and the added depth changes every window and coping detail.
A commercial re-clad generally needs a construction permit, so the owner should check with the local construction office early.
What should the drawings show before panels are ordered?
Settle the joint system and the reveal width first, because they set how every tray is folded. Then the drawings need the panel layout, the clip or extrusion system, and the corner, soffit and window details.
Send elevations, wall sections and the panel spec section through our plans page. We reply with a written quote within 24-48 hours, then prepare shop drawings for approval before any panel is cut. ACM panels typically take 2-8 weeks to fabricate, depending on color. Orders are delivered within about a 5-hour drive of our shop or picked up there. Our submittals and spec sheets page explains the review step, and For Contractors and Builders explains the rest of the process.
ACM rainscreen questions
Is wet-seal ACM a true rainscreen?
Not strictly. In a wet-seal system the sealed panel face is the main weather line, so it works as a face-sealed barrier wall with a backup barrier behind it. A dry-joint system is the true rainscreen, because it expects some water in the joint and drains it from the cavity.
Do dry-joint ACM walls leak through the open joints?
Some water enters an open joint by design. The cavity drains it out at the flashings and the base, and the air and water barrier keeps it off the wall. Leaks come from gaps in that barrier or missing flashings, not from the open reveal itself.
How long do sealant joints on a wet-seal ACM wall last?
It depends on the sealant, the joint design, sun exposure and movement. Plan on regular inspections and on replacing joints as they fail. The sealant maker’s data and the original joint design are the best guide for a specific wall.
Can one building use both wet-seal and dry-joint?
Yes. A common split is dry-joint on the main elevations and wet-seal on column covers, sign bands or canopy edges. The line where the two systems meet needs its own flashing detail, so show it on the drawings before fabrication.
How long does it take to get ACM panels made?
ACM panels typically take 2-8 weeks to fabricate, depending on color. On architectural and commercial jobs, shop drawings are approved first. We send a written quote within 24-48 hours of receiving the plans.
Builders and architects
Have ACM on your drawings?
Send the elevations, wall sections and the panel spec section, and tell us whether the wall is wet-seal or dry-joint. We quote the routed and folded ACM trays, trim and coping within 24-48 hours, prepare shop drawings for approval and flag joint details that need an answer before fabrication.
