Yes, all seams should be treated. The best method is to treat with wedi joint sealant. In cases where waterproofing is not needed such as on a floor outside of a wet area, wedi self-adhesive, alkali resistant fiberglass mesh tape or wedi sealing tape, can be installed using modified thinset mortar to provide a continuous bonding surface. In wet areas wedi joint sealant is the recommended application. Do not add any mesh in the bed of wedi joint sealant except where you need to apply sealant over off angles and transitions. Here you want to use the mesh to provide a better surface for the sealant application. Mesh or any other tape, when added in joint sealant or thinset mortar, does not add additional protection against movement. Tears due to movement happen as cohesive failures between a substrate and the directly bonded material (joint sealant or thinset mortar). Once this is done, the failure cannot be reversed by any presence of mesh or tape. Sealing tape of mesh embedding in thinset will render the flexibility value of such tapes or meshes useless as they are packed into an inelastic material. Mesh and tape usually add only disadvantages such as difficult to tile over higher build up in corners and transitions, or the possibility of water intrusion along mesh lines or through thinset mortar underneath a tape.
Mesh, in the perception of some manufacturers, supposedly acts as “rebar “ or reinforcement for sealants. The perceived benefit would be a better protection against movement. Physics and testing, however, show a much different picture: movement of concrete or wood substrates capable of tearing on sealant to a point at which the mesh is reached or may go into action will have caused tremendous damage by that time. The embedding of mesh in two layers of sealant provides for a sealant bed of a minimum of 1/8”. Sealants of wedi’s class have an elongation potential of about 200-250%. This means they could in this case stretch to about a 1/4” - 5/16” before breaking. The mesh may now prolong this effect. But once a seal or seam is pulled apart by a 1/4” , tremendous damage is done to any installation including wedi systems, mud bed/ liner showers, sheet membrane covered shower products. Therefore it is highly unnecessary to add mesh and the recommendation to add mesh is misleading installers to trust in a perceived benefit that cannot materialize.
When installing the wedi Subliner Dry sheet membrane systems you would want to use the wedi waterproof sealant tape to treat seams or you may overlap the membrane sheets by 2”, thinset mortar applied between overlaps or under sealing tape . However, wedi joint sealant will later be spread and sealed over any exposed seam so water may not wick into thinset mortar between membrane sheets. , follow wedi installation instructions accordingly. To avoid excess thinset mortar at seams and transitions or terminations of our membrane, it is recommended to fold the membrane edge back by 1” and tape into positions. Use joint sealant to glue the edge area down , then seal over the area with joint sealant again.
When working with wedi shower systems, there is no substitute for wedi joint sealant, a sealant and adhesive made under wedi license- and developed by wedi. One of the key important points in a successfully waterproofed shower installation is to safely seal protrusions and installations going through the waterproof walls. Shower valve, shower head , body showers and many other items are very often not appropriately sealed into the system. Water, running below the tile kevel through thinset mortar will find these areas and may easily leak outside the shower. Once the water has exited it may start to compromise the subfloor and/ or framing outside the waterproof shower enclosure. Once the wood structure starts warping or swelling it will start to destroy the shower and previously waterproof installations from the outside going in. It is extremely important to use sealing products such as wedi’s Flexi Collar ( Valve or Shower Head) to address these issues safely. The plumber, when installing seals on his own , will not install protection against the water running behind the tile.