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boxy_brown 03-24-2010 11:17 AM

cutting expansion gaps in underlayment
Hello all. This is my first post here and I'm a diy newbie so please bear with me. I recently bought a house and all of the carpeted flooring was destroyed, and needed to be removed. I also removed some particle board underlayment, under which are wide planks running over the joists. I am planning on putting laminate flooring down in about half of the house, so I chose a smooth plywood underlayment to put over the planks. When reading up on how to do this, I thought the instructions said only to put expansion gaps at the edges of the room, but now everything I'm reading says to put the gaps in between each sheet.

My question is, is it acceptable to use a saw kerf to insert these gaps after the fact? I don't see why not. The only problems associated with this that I can think of would be getting the exact right height on the blade so I don't cut into my planks, and the fact that I wouldn't be able to cut the gaps all the way to the walls.
Any suggestions on this?

oh'mike 03-24-2010 12:31 PM

You didn't mention what kind of "smooth plywood" you put down.

I usually butt the sheets -tight -with out a gap--never had a problem--plywood is quite stable.

boxy_brown 03-24-2010 12:39 PM

I'm not even sure what exact type it is. It came reccomended from the lumber yard as being the best type for a floating laminate floor.

So you don't think the gaps are necessary at all? One friend of mine said he thought the gaps were more for new construction where the house may settle (my house is 40 years old). But most every "how to" resource I look up recommends anywhere from 1/32 to 1/4 of an inch gap in between all the sheets.

oh'mike 03-24-2010 01:05 PM

I've been remodeling for 17 years--and setting tile(which is very unforgiving)

I've never had a problem--nor have I heard that underlayment must be spaced----

Underlayment is used for peal and stick tile--what would that job look like if 'expansion ' joints were used?:laughing:

I don't know any thing except my own experience--I don't space the sheets--never had a problem.


rusty baker 03-24-2010 06:17 PM

Some flooring installers say to leave a gap. But I have installed underlayment for vinyl for over 30 years, and have always filled any gaps with floor fill. I've never had a problem.

boxy_brown 03-25-2010 09:40 AM

Yes, most instructions I'm finding online say to leave a gap, and then fill it with a floor leveling compound.

Thanks for the advice guys. From what I'm reading here I think it will be ok to leave the floor as is.

bernieb 03-27-2010 04:54 PM

My two cents
You're probably going to be using a roll out eighth inch foam pad ,so don't worry about the plywood spacing. When this laminate flooring first came out the sales person told me to use contact cement the floor down and also in the joints........well I did, and got so high from the glue, even with the windows open, but..............12 years later the floor seams are still tight and you can't see the board seams. I put laminate flooring in my house with the pad, but I wish I had put in real wood. Laminate flooring really hates water and it will self destruct with it,plus if you have track in sand .......I give it a year. 72 yearsold and I don't have two cents.....haha

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