Warmboard-R Install Guide

Assembly instructions for retrofit radiant panels

Warmboard-R Panel Description

Warmboard-R is a hydronic radiant panel made from oriented strand board (OSB) with a conductive .025″ thick 1070 aluminum alloy skin bonded to the entire top surface. Each panel type is stamped with a series of aluminum channels on the top surface to hold 1/2″ PEX or PEX-AL-PEX tubing.

Warmboard-R consists of two panel types which weigh approximately 25 pounds, are 13/16″ thick and measure 23 7/8″ x 48″. In a completed assembly, Warmboard-R weighs 3.2lbs per square foot, which includes the panel, tubing and water.

Warmboard-R is typically installed over concrete or subfloor, though is also used in walls and ceilings. Non-aluminum filler panels are also available.

panel type detail

Installation Highlights

  1. Count your panels when they arrive on site and confirm the shipment is correct. If there are any questions or inconsistencies with your plan set, call us immediately.
  2. The existing subfloor should be reasonably smooth and flat prior to the installation of Warmboard-R. Inspect for squeaks and refasten to joists if necessary.
  3. Warmboard-R and the subfloor MUST be dry prior to installation. Warmboard-R CANNOT be exposed to rain before or after installation. 
  4. Gap 1/8″ between panels on the 4′ side and always use the alignment pins when fastening to ensure
    the tubing paths between panels line up.
  5. ONLY use tubing approved by Warmboard, Inc. DO NOT use silicone or other types of adhesives in the tubing channel.
  6. Tubing layouts for Warmboard-R can be quite flexible. Make field revisions as needed but DO NOT exceed 275 linear feet per loop.
  7. Custom routes require a router with a minimum 1.75 horsepower (2.25hp is recommended). DO NOT attempt a custom route without the proper template guide.
  8. When Warmboard is installed over a crawl space or existing subfloor, a minimum of R-19 insulation
    is required beneath the panels to prevent downward heat loss.
  9. Review the installation manual before installing finish floors.
  10. The surface temperature of finished floors is not to exceed 85ºF. This rule applies to the entire radiant industry, and is endorsed by the Radiant Professionals Alliance (RPA) and International Association of Plumbing and Mechanical Officials (IAPMO).
  • Warmboard-R panels are but one component in a complete radiant system. System design should be done in accordance with Radiant Professionals Alliance (RPA) guidelines, manufacturers’ recommendations for ancillary components, and is the responsibility of the system designer.
  • By reading these highlights before proceeding, you will save you time, money and hassle.
  • Warmboard products are required to be installed. and managed by experienced and licensed trade professionals pursuant to current local laws. Failure to use proper installers will void any product warranty.

Approved Tubing

PEX Aluminum PEX tubing, 1/2″ ID

  • Warmboard PEX: PEX-AL-PEX
  • Bluefin: PEX-AL-PEX
  • Mr. Pex: PEX-AL-PEX
  • Watts: PEX-AL-PEX

 

ONLY use the supplied Warmboard PEX-AL-PEX, which has been specified and tested by Warmboard for use with the WCS. 

 

PEX tubing, 1/2″ ID

pex tubing

  • HeatLink FL PEX-a
  • Mr. Pex
  • Rehau Raupex Oxygen Barrier
  • Uponor helioPEX X2
  • Uponor/Wirsbo hePEX
  • ViegaPEX Barrier
WCS tubing

Although Warmboard approves these tubing products for panel projects, they are NOT supported for use with the Warmboard Comfort System. ONLY use the supplied Warmboard PEX-AL-PEX.

Necessary Tools

Tools and Materials

  • Circular saw, carbide blade
  • Router, minimum 1.75 horsepower, 25hp recommended
  • Electrician nailing plates
  • 16oz Rubber mallet
  • Warmboard approved tubing
  • Shop vacuum
  • Drill motor with a 3/4″ drill bit
  • PEX tubing cutter
  • Wax pencil or permanent marker
  • Tubing un-coiler
  • 4″ Grinder or Dremel tool

Warmboard Installation Kit Content

(supplied with each order)

  • Warmboard panel/tubing plans
  • 3 Custom routing templates (wood)
  • 5/8″ Router bit
  • 2 Alignment pins
  • Router template guide
  • Router guide lock nut
Warmboard panel install kit

Installing over Subfloor

Preparation for subfloor installation

It is essential that the existing subfloor is both flat and smooth before the installation of Warmboard.  Inspect the subfloor for evenness along the joists and flatness between the joists.

If necessary, sand the subfloor and install extra blocking below. Inspect for squeaks and refasten with decking screws as necessary.

Cutting and installing Warmboard-R is very straightforward. The panels can be trimmed with a standard skill or table saw and will rip just like ordinary OSB. We recommend cutting with the aluminum side down to help avoid burrs.

Warmboard-R installation

Method 1: Screw Only

Use a #8 x 11/2″ GRK R4 Multi-Purpose screw (or equivalent) with a top 1/2″ smooth shank. Fasten with a pattern of 3 rows of 4.

  • No pre-drilling required
  • Self-counter sinking
  • No adhesive needed

Method 2: Nail and Glue

Use a construction adhesive designed for bonding OSB to plywood (Loctite PL Wood Adhesive or equivalent). Follow all directions specified by the adhesive manufacturer.

For nailing, use a ring shank or a screw nail. To determine the appropriate length of the nail to use, evaluate existing thickness of subfloor and add 13/16″. Fasten nails with a pattern of 3 rows of 4.

panel over subfloor

  • Warmboard-R and the subfloor MUST be completely dry, with a moisture reading between 8-12% before, during and after installation.
  • DO NOT expose Warmboard-R to rain before or after installation.
  • It is crucial to use the alignment pins to line up the channels from panel to panel.
  • Cut panels with the aluminum side down.

Installing over Slab

Concrete Slab Requirements

Whether a remodel or new construction, slabs must be flat and smooth before any panel installation steps can be taken. Where slabs do not meet this criteria, take the necessary steps to produce a flat and smooth surface.

Once determined to be flat and smooth, the slab should be checked for moisture.

If the slab is severely unlevel, consider forgoing a leveling product and instead choose the sleeper installation method noted in this guide. Scribe and cut the sleepers to create a level plane for the Warmboard-S installation.

Moisture Testing

Like any wood product, if Warmboard panels are exposed to standing water or moisture intrusion, the panel can swell and rot. Do not install Warmboard panels if these environmental conditions are possible during or after construction.

It is best practice to test both new and existing slabs for moisture. A newly poured slab must cure for a minimum of 30 days before a moisture test should be conducted. As the slab dries, periodic tests will likely be necessary before the slab is dry enough for the vapor retarder and Warmboard panels to be applied.

The following tests are useful in determining current slab conditions, though some tests are more relevant than others. The outcomes of these moisture tests can be affected by the weather conditions on the job site. Generally, these tests will want to be completed in mild weather such as 75° (+/- 10°F) and 50% (+/- 10%) relative humidity, but always verify with the selected testing procedures.

If not performing a moisture test, we recommend giving a new slab at least 90 days to cure before moving forward with the installation in conjunction with the use of a Class I vapor retarder.

  • Similar to the NWFA guidleines, the slab should be flat within 1/8″ per 6 feet.

1) ASTM F1869-22: CALCIUM CHLORIDE

This test determines the moisture vapor emission rate (MVER) from a concrete slab. It produces quantitative results which represent how much water vapor is leaving the slab at the time of the test.

This test is simple, inexpensive, and readily available for purchase through online retailers. Instructions are provided in the test kit and can be found in documentation provided by the ASTM.

The test should be conducted three times in the first 1,000 sqft of concrete slab, then tested once every 1,000 sqft after that. Compare the test results to the requirements/specifications of the selected vapor retarder as well as the finish flooring to be installed above the Warmboard panels.

Generally, an acceptable test result will be: < 3 lbs/1,000 sqft/24 hrs.

2) ASTM F2170-19A: RELATIVE HUMIDITY PROBE

Relative humidity moisture tests using in-situ probes return quantitative values for the moisture content within the core of a concrete slab. The in-situ probe measures the relative humidity of the slab at 40% of the slabs depth (20% for suspended slabs).

This test is more expensive in comparison to the Calcium Chloride test, but provides a more thorough evaluation of the slab condition. Instructions are provided in the test kit and can be found in documentation provided by the ASTM. This test should be conducted three times in the first 1,000 sqft of concrete slab, then tested once every 1,000 sqft after that. Compare results to the requirements/specifications of the selected vapor retarder as well as the finish flooring to be installed above the Warmboard panels.

Generally, an acceptable test result will be: <80%

3) ASTM F2659-23: ELECTRONIC MOISTURE METER

Non-destructive electronic moisture meters are an effective way to evaluate the surface conditions of a concrete slab. Use this process to determine testing locations for ASTM F1869-22 and ASTM F2170-19A test methods.

As the test measures only surface conditions, it will not offer a reliable insight to slab conditions. Instructions for this test can be found in documentation provided by the ASTM.

This test should be conducted three times in the first 1,000 sqft of concrete slab, then tested once every 1,000 sqft after that. One test consists of three to five readings within a 1 sqft area at each location.

4) ASTM D4263-83: PLASTIC SHEET METHOD

While this test indicates the presence of capillary moisture in a slab, it offers little information on the extent of potential moisture issues. To begin, place an 18″ x 18″ clear plastic sheet on the slab and tape down on all sides. Do this once per every 500 sqft of the slab. Do not allow the sheet to come in contact with direct sunlight or excessive heat.

After 16 hours, remove the plastic and examine both the sheet and concrete for signs of moisture. If there is condensation on the sheet or the concrete appears darkened, moisture is present in the slab.

  • This method may yield a false result in cool conditions should the concrete retain moisture and fail to condense on the plastic.

Slab Assemblies

Vapor Retarders Above Slabs

Regardless of whether or not moisture tests were successful or an underslab vapor retarder is present, Warmboard always recommends applying a Class I vapor retarder above a concrete slab before installing Warmboard panels.

Since the conditions of slabs can change over time (for better or worse), it is best practice to protect against possible moisture intrusion in the slab.

As defined by the The ICC, a Class I vapor retarder has a permeability rating of < 0.1 perms. Various liquid vapor retarders, as well 6- or 10-mil poly sheeting, meet this specification. The Technical Data Sheet (TDS) for a vapor retarder will generally note its permeability rating.

Vapor retarders have their own specific installation requirements. Ensure slab conditions meet the requirements from the vapor retarder’s TDS. Apply the selected vapor retarder before moving on with the rest of Warmboard panel assembly. If using poly sheeting, overlap the seams 24″ between sheets.

Recommended: Direct Fasten

For slab applications, the basic assembly method is to fasten Warmboard-R directly to the slab. This method is best when there is existing insulation beneath the slab.

After installing the selected vapor retarder, continue with the Warmboard-R installation fastening to slab using split drive anchors, powder actuated fasteners, or concrete screws.

Use a minimum of 9 fasteners per full panel, using a pattern of 3 rows of 3.

Warmboard-R-slab-direct-fasten

  • The slab MUST have sufficient drainage from rain and snow at all times. Failure to provide sufficient drainage will void any product warranty.

Alternative: Insulated, Warmboard-R On Floating Subfloor 

With the growing demand for energy-efficient and sound proofed flooring products, it’s increasingly common for contractors to float flooring and subflooring assemblies.

An established subfloor assembly, which can be suitable with Warmboard-R panels, consists of the following:

  1. High strength rigid foam insulation is laid across the slab. In place of a vapor retarder, tape all the seams between the foam sheets to generate a continuous surface. 
  2. Two layers of plywood (1/2″ minimum) are placed above the insulation. The top layer is glued and then screwed perpendicular to the lower layer.

Warmboard-R can now be installed onto the newly built subfloor following the instructions for subfloor applications. Fasteners for the subfloor, Warmboard-R, and flooring should be sized as to not puncture the insulation and tape.

Warmboard-R-slab-on-floating-subfloor

  • The slab must have sufficient drainage from rain and snow
    at all times. Failure to provide sufficient drainage will void
    any product warranty.

Fastening to Slab

Fastening to Concrete

Pay close attention to the Panel Layout in the plan set while selecting panels to place. Align the panels as you place them by using the alignment pins supplied in the install kit. Fasten each panel before moving onto the next. Any drilling should be done with the Warmboard panels in place (drilling the slab before placing the panels is not recommended). Due to the number of fasteners necessary, using a rotary hammer and SDS bit is recommended when drilling the slab.

Holes for anchors should be deeper than the required fastener embedment. Check your fastener‘s installation instructions to be sure of hole depth. Be sure to keep the bit and hole clear of debris while drilling. Finally, use a shop vacuum to remove the remaining dust from the holes.

METHOD 1 Split Drive Anchors (Flat Head)
Requires drilling each hole.

Use a sledge hammer to drive the anchors into the slab through the holes drilled for the fasteners. This option is recommended.

METHOD 2 Concrete Screws
Requires drilling each hole.

Simply drive the concrete screws into the slab through the holes drilled for the fasteners. Concrete screws are known to bind on excess debris. Ensure the holes are clear as possible before install. For a higher price point, some companies produce heavy duty (HD) concrete screws which reduce the likeliness of a screw stripping out the concrete.

METHOD 3 Powder-Actuated Fasteners
Does not require any drilling.

Drive these fasteners directly through the panel into the slab below. Select a fastener without a washer in order to maintain a flat panel surface. This fastener type may not be the best choice for older slabs as concrete hardens over time.

This option is recommended.

  • Flat Head Split Drive Anchors will save you many hours of labor, but may be difficult to find in retail locations.

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