Cumaru is a very dense, very hard wood. Use of some specialized or higher grade tools may be necessary for good results. This page will give you an overview of handling and building suggestions that will help you achieve excellent results when building your Cumaru deck.
CUMARU DECKING INSTALLATION
Cumaru is a very dense, very hard wood. Use of some specialized or higher grade tools may be necessary for good results. This page will give you an overview of handling and building directives that will help you achieve the best results when building your Cumaru deck.
Prior to Installation
Always check with local building codes and an architect prior to constructing. Follow all building codes that apply in your area. Since there are many different variables one can encounter on an installation project, it is your responsibility to test the material for suitability for your project prior to constructing. Follow all manufacturers' installation instructions for the individual products used on the project. If any building codes or manufacturers installation instructions contradict or differ from information provided by AdvantageLumber.com, contact us for written clarification prior to starting your project.
Application
Our Cumaru decking is air dried for outdoor use. Air dried Cumaru lumber is suitable for many outdoor applications such as decks, siding, benches, docks, playgrounds, flower boxes, or other outdoor furniture.
Standard & Pregrooved Decking
Our standard and pregrooved decking are both great choices for many outdoor deck and dock applications.
Tongue & Groove Porch Decking
Tongue & Groove Porch Decking is for use under covered porches & covered patios only. Installing tongue and groove on a deck without a roof covering the deck surface will cause problems such as allowing excessive water to collect and cause the material to cup, swell, and buckle.
Storage and Handling
Cumaru decking should be allowed to sit where it will be installed for 7 days prior to installation in order to get acclimated to your local temperature and humidity levels. DO NOT store the decking directly on the ground, or directly on top of a concrete surface. DO NOT store the material for more than 30 days prior to use without first consulting with a sales rep at advantagelumber.com that your storage conditions are optimal. The decking should be elevated at least 12" off the ground during acclimation. To ensure the bottom boards are well ventilated, place the decking on top of blocks of wood. DO NOT cover decking material with plastic or a tarp during this acclimation period. Covering with a tarp/plastic will trap moisture in and cause stability issues. Covering the top of the pile with a sheet of plywood to shed the water is recommended. Keep material dry until installation. Also keep stickers (or wood shims) between layers of boards to allow proper air flow (see image below). DO NOT store the material in a garage or any other enclosed area.
Framing and Span Requirements
| Decking Dimension | Maximum Joist Spacing |
| 1x4 | 16" |
| 1x6 | 16" |
| 5/4x6 | 24" |
| 2x6 | 32" |
Deck Pitch
Ensure the deck substructure is pitched away from the house to allow for adequate water runoff. We recommend a minimum pitch of a 1/4" per 10 ft. for proper drainage on Standard and Pregrooved decking. For Tongue and Groove decking, a more aggressive pitch is recommended. We highly recommend using a 1/4" per foot slope. Framing material should be installed with the crown up (humps up) to aid in water draining off the surface material. Framing lumber can crown 1/8" or more, and may lead to standing water. Any standing puddle of water can cause surface decking to cup.
Gap Spacing
When installing Cumaru decking, be sure to leave a gap between deck boards of 3/32". The difference in gap spacing is to ensure that the decking has room to expand and contract depending on the material used and the environment where it is installed. This also allows for proper air circulation. Average shrinkage is approximately 1/8" on 4" wide boards and 1/4" on 6" wide boards. Shrinkage may vary depending on climate, installation site, and method of use.
Ventilation
Installing hardwood decking above a concrete pad is NOT recommended. Hardwood decking should never be installed directly over concrete due to moisture retention. Any hardwood decking installed over a new or aged concrete pad will cause the deck boards to cup and/or crown.
Cutting & Drilling
Due to the very hard nature of Cumaru, premium carbide tipped saw blades are recommended for cutting. Brad point drill bits or fostner bits provide cleaner holes than standard HSS twist bits.
End Sealing
Our Cumaru decking is shipped with the end grain sealed with a clear wax to prevent any end checking. Fresh cuts should be sealed within 24hrs with end grain sealant. We sell end grain sealant by the quart, which is typically enough for 500 sq.ft. of decking. The end grain sealant is simply applied with a paintbrush and dries clear. DO NOT apply end seal to the surface of the decking. Any sealant that gets on the surface should be wiped off immediately.
Fastening
Use only stainless steel fasteners to fasten hardwood decking or dimensional hardwood. Use of fasteners or screws made of anything other than 305 or higher grade stainless steel will cause unsightly staining and discoloration to the wood around the fastener and the fastener could corrode and fail prematurely. When fastening deck boards pre-drilling is required. Pre-drill all your holes with the appropriate sized drill bit for your screw size. Failing to predrill can cause the wood to split which can cause irreversible damage to the deck boards and make the boards come loose over time.
The use of Ipe Clip® hidden deck fasteners to fasten the deck boards is highly recommended. Ipe Clip® hidden deck fasteners keep the deck surface blemish free. This deck fastening system also allows the wood to expand and contract on its width without putting undue shear pressure on the screws when wood expands/contracts. Using Ipe Clip® hidden deck fasteners instead of face screwing can help keep water from penetrating the surface of the wood. Ipe Clip® deck fasteners also helps keep the deck surface splinter free. If you choose to install decking using Ipe Clip® hidden deck fasteners, please refer to and follow the installation included in the system's packaging.
Finishing
Because of Cumaru's natural density and alkaline characteristics, many oil and water based finishes will not dry properly when applied. We recommend that you test any product on several sample boards to determine compatibility. The finish we sell and recommend is Cumaru Oil?. We do not recommend the use of other finishes. Applying a finish approximately every two years (depending upon your local climate) can help keep the beautiful dark brown color. If you decide to let your deck weather, it will turn a silvery gray similar to teak. We recommend that you apply a coat of finish initially after deck installation, regardless of the final color desired. This can help ensure that the Cumaru retains its oils and stability. For low ventilation applications, we recommend finishing deck boards on all four sides prior to installation but after acclimation.
Gluing
If the need arises to glue your Cumaru, waterproof glues, such as Gorilla brand polyurethane can be used with satisfactory results for gluing plugs into deck boards. Epoxy glues are also very suitable and can be dyed to black, brown or other colors to match your Cumaru deck. Epoxy produces a very strong waterproof bond, particularly important for gluing posts.
WHICH DECKING PROFILE IS RIGHT FOR YOU?
Standard & Pregrooved Decking
Our standard and pregrooved decking are both a perfect choice to be installed on outdoor decks and docks. When installing outdoor decking be sure to leave a gap between deck boards of 3/32" for air dried material or 1/4" gap for kiln dried material. The difference in gap spacing is to ensure that the decking has room to expand and contract depending on the material used and the environment where it is installed.
Recommended Method
Ipe Clip® Method: The Ipe Clip® system uses high strength plastic clips that insert into slots cut into the edge of the deck board which then rests on top of a joist. A stainless steel screw (supplied with each Ipe Clip® fastener) is then screwed down into the joist. We recommend the Ipe Clip® system as many other fastener systems install from the bottom side of the deck, requiring screwing into the bottom of the deck board. With the Ipe Clip® system no screws or holes show from the surface.
Optional Methods
Face Screw / Plug Method: Countersink 3/8" holes into face of deck boards. Predrill 1/8" pilot holes completely through the deck boards. Screw the deck boards down with stainless screws. 3/8" Cumaru plugs are then glued into the holes with waterproof glue (i.e. Gorilla brand glue, Epoxy, etc.) Plugs are then knocked off with a chisel and sanded smooth with 80 grit sandpaper ( a round orbit sander works great). We manufacture Cumaru plugs in 3/8" diameter with a small taper.
Finish Screw Method: Stainless steel #7 or #8 trim head screws are screwed into the face of the decking. Recommended two per joist. The trim head screw is very small and only slightly noticeable. Torx drive screws will strip out less than square drive.
Tongue & Groove Porch Decking
Enjoy Your Deck Year-Round... Decks are not just for summertime anymore! We now offer our customers Tongue & Groove Decking in four unique species. Our T & G decking is the perfect option for any covered porch. So forget about only enjoying your deck in the summertime. Give yourself a deck that you can love anytime of the year. T&G decking has no gap spacing in between the boards after it is installed, similar to interior hardwood flooring.
T&G decking will need to be installed directly on top of the floor joists, not on a sub floor as the material will need cross ventilation underneath it. The material will need to be under cover and have a pitch to allow for drainage. For installation we suggest that you pre drill a hole on a 45-degree angle where the tongue and the face meet, you will see a slight v-groove in this corner. Then, on that same 45-degree angle drive a trim head screw through the pre drilled hole, through the deck board into the floor joist. We carry a large variety of stainless steel trim head screws that a perfect for this application. The trim head screws are required because the head will sink into the corner where the v-groove is. This sinking action will allow the next deck board to slide into place and will perfectly conceal the previously installed screw head.
Advantage Trim & Lumber Co. provides this information as possible suggestions only and will not be held liable for your project's suitability or should you choose not to obtain the required permits, or if you fail to comply with all zoning ordinances and building codes.
Conclusion
If you have any questions, contact us for written clarification prior to starting your project. By purchasing material from AdvantageLumber.com, you agree to comply with our Terms & Conditions.