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Xtreme Bedding Compound: (VDW 480 Trass Bedding)


The PHNA Xtreme Bedding Compound is a high-strength, highly-plastic modified, frost-resistant drainage mortar for the laying of natural stone, slabs, tile, and concrete pavers.

  • Highly water-permeable
  • Frost and de-icing salt resistant
  • No efflorescence despite rapid hardening
  • High-quality plastic coating resists capillary effect
  • For light to heavy traffic loads
  • Compressive strength up to 5500 psi
  • Eliminate the need for a concrete sub-slab
  • Can be grouted 24 hours after installation
  • Compatible with radiant heating/snowmelt systems

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SKU: GFTK480EBC Category: Brand:

VDM 480 Mortar: What Is a Mortar Bedding System? 

The construction industry has witnessed a significant transformation over the years, and this is primarily due to the emergence of new building materials and techniques. One material that has gained popularity in recent years is Trass Bedd VDM 480 bed mortar. VDM 480 is a high-quality plastic-modified jointing compound that contains trass for drainable bedding mortar. This type of mortar is known for its superior water resistance, durability, and strength when compared to other methods. 

Trass VDM Bedding mortar is a high-quality, pre-mixed, cement-based mortar that contains volcanic ash known as “Trass.” Trass is a natural pozzolan formed by the volcanic ash of Mount Vesuvius. Trass has been used for centuries in construction due to its exceptional properties, including high water resistance and strength. 

GFTK 480 mortar bedding system

Benefits of Trass VDM 480 Mortar Bedding


Highly water-permeable

Being permeable means that water will flow through the compound.
This is especially important to have in freezing and thawing climates.
This keeps the stones dry while reducing water runoff from rain or irrigation systems, which allows water to drain into the ground. This water soaks into the earth, recharging our groundwater and slowing erosion.

freeze resistant

Frost and de-icing salt resistant

This Bedding System is frost and de-icing salt resistant, due to its permeable nature. Water and other solvents will flow through it making it cleaner and allowing the stones to stay dry and worry-free.

open after 24 hours

Can be grouted 24 hours after installation

This System sets up quickly once allowed to dry.
With quick-drying, projects can be completed faster allowing for more jobs with better quality to be completed. This means you can get on to the next project faster.

underfloor heating

Compatible with radiant heating/snowmelt systems

This Bedding System is suitable for use with under surface heating. While also being permeable, allowing surfaces to dry and be warm without shifting or cracking.

Technical Data:

Application Time

  • Approx. 1 hour at 20°C | 68°F* application temp.
  • *Quick hardening at higher temperatures and slow hardening at lower temperatures.

Application Temperature

  • 5-25°C | 41-77°F (Do not lay onto frozen ground.)

Material Requirement

  • Clean 1/8″ – 3/8″ crushed aggregate mixed at 1:4 ratio
    • 1 part Xtreme Bedding Compound to 4 parts aggregate.
      • (approx. 220 lbs. aggregate per each 55 lb. bag of bedding compound)
  • *A mixing ratio of 1:6 is possible and suitable for light pedestrian loads

Water Addition

  • Approx. 11 liters | 2.9 gal. of cool, clean water per 25 kg | 55 lb. bag of mortar mixture

Compressive Strength

  • 2900 – 5500 psi at 3 and 28 days (dependent on filler material and mixing ratio)

Flexural Strength

  • Approx. 1015 psi


  • Cement, according to EN 197, Trass, according to DIN 51043, and special additives

Storage Life

  • 1 year if stored unopened in sealed and undamaged packaging.
  • It must also be kept dry and frost-free.

Xtreme Adhesion Elutirant Mixing and Installation Instructions

1. Construction Site Requirements

  • The subsurface must be made load-bearing, firm, and water-permeable.
  • Ensure drainage through permeable subsoil or a sufficient drainage gradient.
  • Water impermeable load distribution layers, such as areas with house utility connections or any slab coverings that are laid, must have a slope of at least 1.5–3.0%.
  • In case of any watertight outdoor areas and levels where water flows or partial puddles form,
    it is recommended to install a suitable capillary-breaking drainage mat.
  • Ambient and substrate temperature should be 41-77°F, and the process should be carried out in dry weather.

2. Preparation

  • 1 volume part Xtreme Bedding Compound
  • 4 volume parts suitable aggregate (i.e. 1/8″ – 3/8″ clean crushed or rolled grit/gravel)
  • 11 liters | 2.9 gal cool, clean water per 25 kg | 55 lb. bedding compound
    – Make a note of wet/damp aggregate and reduce water consumption accordingly.
  • Using a compulsory mixer or gravity mixer, mix the Xtreme Bedding Compound in a ratio of 1:4 with suitable aggregate and water.
    • Mix so that it becomes earth-moist; the total mixing time 4–5 minutes.
  • First add the aggregate and approx. 75% of the water to the mixer,
    • followed by the Xtreme Bedding Compound.
  • Little by little, continue to add the remaining water to the mixture until the mortar is slightly shiny and can be formed into a loose ball.
  • For smaller batches, mixing can be completed in a wheelbarrow or mortar tub.
  • These methods may require a longer mixing time to achieve a homogeneous mortar.
  • After mixing, the mortar is ready for immediate use. It is recommended to use the entire bag of bedding compound when possible, but for smaller batches, precise quantities should be weighed out.
  • Expect approx. 2.5 – 2.7 ft3 of coverage per unit mixed at a 1:4 ratio.

3. Application

  • Apply the mixed bedding mortar manually in layers of minimum 1.5″ and maximum 4″ thickness.
  • In the case of pavers or stones that are uniform in thickness, the bedding mortar can be leveled to the required layer thickness using screed bars.
  • The underside of paving units needs to be pre-treated with our Xtreme Adhesion Elutriant (vdw 495)
    and set at the correct height before hammering into place with a rubber mallet or dead-blow hammer.
  • The joint area must be water-permeable and therefore also free of Xtreme Adhesion Elutriant universal bonding bridge.
  • Post-treatment:
  • The bedding mortar must be protected from drying out too quickly, and therefore avoiding excessive heat.
  • After installation, the bedding mortar must be protected against drying out for a sufficiently long period, but at least 24 hours.
  • Covering with a tarp may be necessary for this time.
  • The surface should also be covered in the event of adverse weather, such as sustained rainfall.

4. Important Information

  • The surface can be walked on after 24 hours or after the mortar has hardened. Grouting can also be carried out at this time.
  • Full resilience will be reached after 7 days, but vehicular areas should not be opened to traffic until the grout has also sufficiently cured.
  • Please refer to the datasheet of the grout used for this information.

Weight 55 lbs

Begin Your Project journey at our showroom

Visit our 5,000 square feet indoor hardscape materials showroom in New Holland, PA where you will find hardscape layouts, outdoor kitchen ideas, patio paver designs, patio lighting features, and our high-quality patio furniture all on display. Find the colors and textures that best complement your style, and a guide to help you choose the best combinations for your hardscape project in New Holland, PA. Here you will find hundreds of hardscape materials on display along with a full display of backyard and patio ideas.