Expansion Gap Question

[go_hercules]

Hardwood, engineered hardwood, laminate, and vinyl plank all require an expansion gap around the perimeter. I can understand this on a floating floor, but they require it even with nail down, or glue down. What I don't get is this: if the board is glued down, then to expand at the end of a row even a little, the glue joint would have to fail. I don't see how a glue joint could stretch a quarter of an inch and not fail. The same with nailing - for the end of the row to expand a quarter of an inch, the nail would have to break off. So I don't see how it makes sense to leave much of a gap if gluing or nailing. What am I missing???

 

[Floorist]

The flooring and subfloor both expand. in fact, all wood expands and contracts.

 

[go_hercules]

So then why leave a large expansion gap? Are you saying it's not necessary? And if it is necessary, then my question remains.

 

[Dan]

Expansion space is required at all vertical obstructions. Floorist is correct when he stated all wood expands and contracts. ( I prefer the terms shrink and swell.) This shrink and swell involves your whole home.

If you don't want to leave an expansion space because you don't understand how it is necessary, don't. Just don't expect to have a warranty from the manufacturer if their installation instructions are not followed.

 

[go_hercules]

I understand what you guys are saying, wood expands and contracts. Fine, but let's say you glue down on concrete. The only way for the wood to expand then would be for the glue to let loose. And if you nail down onto a wood subfloor, you are forcing the subfloor and flooring to move together. So if they are forced to move together, why do you need a large gap? I mean, either everything moves together (subfloor and flooring) or they don't. If they move together, then I just don't see the need for a large gap. And if they don't move together, then in a glue or nail down, something would have to let loose for one to move and not the other.

 

[DarisMulkin]

Your whole house expands and contracts with the temp changes. Some areas may do more or less. That is another reason for the gap.

 

[go_hercules]

Okay, maybe I am making the question too complicated. I will try one simple question to see if it helps: If glued-down wood on concrete expands one half inch over a long span, what happens to the glue joint?

 

[DarisMulkin]

probably nothing as it is the concrete that is moving. Wood has to go with it if anchored. Just my thoughts. That is why they have expansion joints and saw cuts in concrete. There are more than one type of expansion joints in concrete. Commercial installers have to know how to deal with each type.

 

[Ernesto]

Engineered moves more in length, solid move more in width. Glue down engineered over concrete really won't move much at all. At transitions with G/D on concrete I will typically only leave a 1/8 inch gap, fill it with some foam backer rod and use matching grout caulk over the backer rod.

 

[go_hercules]

Ernesto, is the backer rod and caulk stiff enough to prevent the movement you left with the small gap?

 

[Ernesto]

It flexes. You don't want it rigid.