Suggestions on sealing drywall at floor?

[Beatles]

I am almost finished my live sound room, and firstlly, I'd like to thank all the people who have posted their questions and the answers that have been provided by the resident experts. I followed all the posts recommending how to build a studio, and did what the pros suggested....staggered studs, RC, rigid insulation, double drywalled (offset) and used acoustic caulking on just about everything that had an opening. Now here is my question. What would be the best way to seal the gap between the floor and the bottom of the drywall? There is about a quarter to a half inch gap. Should this also be caulked with acoustic caulking? Thanks again.

 

[Rod Gervais]

I am almost finished my live sound room, and firstlly, I'd like to thank all the people who have posted their questions and the answers that have been provided by the resident experts. I followed all the posts recommending how to build a studio, and did what the pros suggested....staggered studs, RC, rigid insulation, double drywalled (offset) and used acoustic caulking on just about everything that had an opening. Now here is my question. What would be the best way to seal the gap between the floor and the bottom of the drywall? There is about a quarter to a half inch gap. Should this also be caulked with acoustic caulking? Thanks again.

Yes it should - ideally you would have done this one layer at a time - but now just make sure to do a great job of it.

BTW - make sure to use backer rod - otherwise the joint may wel fail.

Rod

 

[Beatles]

Thank you Rod

I'm not sure what a backer rod is, but if you suggest it, I will do so.

 

[Rod Gervais]

Thank you Rod

I'm not sure what a backer rod is, but if you suggest it, I will do so.

Backer rod is a foam rod that comes in a coil - sort of like foam rope.

You place it in the joint before caulking - and it makes sure that your caulk joint is only 2 sided - which is what you need between 2 materials that will exhibit movement to any extent. A 3 sided joint will fail.

Rod

 

[Beatles]

Thanks again for your help Rod. Now that I understand, I can move forward.

 

[fraserhutch]

I was told long ago by an acoustician that you do not actually want to connect the wall to the floor. This way you also help minimize waves travelling from the floor to the walls. My walls do not actually touch my floor, and neither does my moulding. I left a 1/16" gap.

Don't know if you guys would agree, but it works for me.

 

[Innovations]

I was told long ago by an acoustician that you do not actually want to connect the wall to the floor. This way you also help minimize waves travelling from the floor to the walls. My walls do not actually touch my floor, and neither does my moulding. I left a 1/16" gap.

Don't know if you guys would agree, but it works for me.

he had half the answer. If you don't fill the gap it will be a flanking path for sound. That is what the accoustic calk is for. to fill the gap while being flexible enough to limit the sound travleing from the floor to the wall. Besides it is the sound traveling THROUGH the wall that is your primary concern.

Correct about backing rod. But the real purpose is to fill deep cracks so that the caulk has a relatively equal height/width ratio. A really deep blob of caulk is likely to separate from one side or the other.

 

[fraserhutch]

he had half the answer. If you don't fill the gap it will be a flanking path for sound. That is what the accoustic calk is for. to fill the gap while being flexible enough to limit the sound travleing from the floor to the wall. Besides it is the sound traveling THROUGH the wall that is your primary concern.

Correct about backing rod. But the real purpose is to fill deep cracks so that the caulk has a relatively equal height/width ratio. A really deep blob of caulk is likely to separate from one side or the other.

Well, now that I think about it, I believe he did have me caulk the joint between the wall and the floor, so I may have been mistaken in my original post. I am not 100% sure though - there was soo much to do and so many instructions I think it was the hardwood flooring thatshould not touch the wall. I wish I could remember for sure.... He was very adamant about the moulding not reashing the floor though.

 

[Rod Gervais]

Correct about backing rod. But the real purpose is to fill deep cracks so that the caulk has a relatively equal height/width ratio. A really deep blob of caulk is likely to separate from one side or the other.

Innovations,

Sorry sir - but you are mistaken - a deep blob with a two point joint will not fail if properly installed and jointed. But 3 point joints - especially with construction that will exhibit any movement - are headed for failure.

this is straight from doityourself.com:

Two-point adhesion:Sealants need to be applied so that they only adhere to the two opposing sides of a properly configured joint (usually created by using backer rod). If this rule is not followed (as in what is termed "three-point adhesion"), there is often a high risk that extreme and unforeseen stresses can be induced at certain points along the bond-line that can cause failure. The use of backer rod helps to insure two-point adhesion.

This from Sherwin WIlliams:

• Joints in excess of 1/2" in width or depth. If the opening is 1/4" or greater, for maximum performance, prevent three-point adhesion with backer rods or bond breaker tape. Three-point adhesion problems occur in cracks when the sealant adheres to the walls and the bottom of a crack, and a significant amount of flexibility is lost. Two-point adhesion – wall to wall in a crack – using backer rods or bond breaker tape offers the maximum flexibility and performance.

This on backer rods from Sashco Sealants - a sealant manufacturer:

It provides a "bond-breaking" surface at the rear of the joint or crack that prevents the sealant from establishing three-point adhesion (see "two-point adhesion") - which, if allowed to occur, can lead to early failure.

Here are links if you wish to read for yourself:

http://doityourself.com/energy/caulkingglossary.htm#Two-point adhesion

http://www.sashcosealants.com/home_improvement/library/caulking101.shtml

http://www.sherwin.com/pro/problem/problems/sw_pro_ps_int_ext_layout_7_7807_4157.jsp

If you'd like I could post the comments regarding this from the AIA (Architects Institute of America) tomorrow - I don't have that data today.

Now - if you have any information from reliable sources that would back up your statement - I would be happy to look at them - but shy of that, I stand by my statements.

Sincerely,

Rod

 

[Beatles]

Thanks again Rod. I picked up some backer rod at HD and installed around the perimiter of the room. I read your links and now have a better idea of how to do the caulking and understand the 2 point vs. 3 point joint.WIll be doing the caulking tonight. Glad I asked.

 

[Rod Gervais]

Thanks again Rod. I picked up some backer rod at HD and installed around the perimiter of the room. I read your links and now have a better idea of how to do the caulking and understand the 2 point vs. 3 point joint.WIll be doing the caulking tonight. Glad I asked.

Beatles,

Glad I could be of assistance.

Rod