EIFS – Floor line joints

A situation may arise where a designer, home or building owner doesn’t want to use joints at floor lines for aesthetic reasons.

Some materials expand when faced with temperature variations, and wood is one of them. When two floors meet on the exterior wall of a building or home with wood framing, floor joints are usually installed to prevent the expanding between floors and subsequent cracking of the Exterior Insulation Finishing System lamina. Often, floor line joints are necessary but there are certain times you may be able to avoid using them or be able to utilize other methods.

Factors that affect the expansion of wood

• Seasonal climate of the area.
• The size of the wood.
• The species of the wood.
• The amount of moisture absorbed by the wood (the moisture content of wood is rarely constant. A piece of lumber may arrive from the source with a particular moisture content, but then dry and shrink after installation. If it comes in any contact with water in the future, it will absorb a lot of it).
• The direction of the grain of the wood.

Force direction in an EIFS wall

The combination of shrinking and expanding wood as well as rim joists at the floor line will create a compression force that is constant and directed at the floor line. The EIFS itself is able to absorb some of this force, but not all of it. A sealant joint placed at the floor line will give the wall the flexibility it needs, otherwise the combined stress factors will lead to cracking or delamination.

Sometimes aesthetic reveals (or “aesthetic joints”) are placed horizontally across an EIFS wall, but these are not adequate floor line joints. Aesthetic reveals are just for decoration, and don’t offer the wall any movement. The type of joint needed at floor lines is a durable sealant joint that can allow for movements up to and larger than a quarter of an inch.

These sealant joints are not only suggested by manufacturers of EIFS, they’re often required.

Floor line joints = only EIFS?

For the most part, floor line joints are semi-unique to EIFS, as it’s generally seamless. Other wall claddings have enough horizontal seams to allow for expansion and shifting within the wall of he building on their own.

If floor line joints are not used

If joints are not going to be used, or they are not already in place on a pre-existing EIFS wall, there are some ways to avoid future cracking.

• Strengthen the lamina: A stronger lamina will not crack as easily if no floor joints are used. One could achieve this by using a stronger, heavier reinforcing mesh.
• Avoid seams at the floor line: If the EIFS foam completely covers the floor line and does not end there and continue as a separate piece on the next floor, the foam will keep the floor line stronger.
• If the wall has not cracked: On a pre-existing wall without floor joints, the lamina may have held up for a period of years without cracking. If it isn’t broken, don’t fix it.

EIFS with drainage

Both the options of letting water run down to the bottom of the wall for draining or draining water at each floor line are available. EIFS with drainage prevents a complicated situation, and each material, including whichever water-resistive barrier as well as the individual drainage components of each system must be taken into consideration when determining whether and how to use floor joints.

Moist climates versus dry climates

In moist climates when the lamina cracks, water intrusion problems become a serious concern. This water intrusion has a domino-like effect – if water gets into the wall and it cracks, the crack will become larger because of the absorption into the wood, which swells and makes the crack larger, allowing for even more water intrusion.

In dry climates, water intrusion issues are less significant, and if cracks occur they are easier to repair using expansion joints.

If aesthetics are the only reason using floor line joints is seemingly debatable, a floor line joint can be created and still covered with a separate piece of foam, coated normally to blend into the rest of the EIFS wall. This hidden floor line joint will still function normally because the foam piece covering it is not attached to the wall above or below.

However, despite the risky attitude towards floor line joints that is found with some people for design purposes, all one has to do to convince them otherwise is refer to the EIFS manufacturer’s instructions. If they require floor line joints, which they more than likely will, not using them will void the manufacturer’s warranty and the designer, building or homeowner will pretty much be out of luck if the EFIS cracks due to the thermal shifting of the wall materials.