Is painting the plasterboard/drywall beneficial?

TerrorFiend · Post by **TerrorFiend** » Thu Aug 26, 2004 9:53 am

Is it, or is it not worth putting a few coats of paint on a wall that will be covered up before the project's completion?

I've heard that painting concrete blocks can reduce TL by a few decibels and was wondering if the same applies to plasterboard.

giles117 · Post by **giles117** » Thu Aug 26, 2004 9:58 am

Maybe it does, but I never wasted a drop of paint for 1 db of Suppossed Tl when I put up my room and have 0 regrest. LOL

I didnt even waste the time to mud the place. After all the layers of drywall are offset.

What I did do was run acoustical sealent on the final layer at the seams and the edges.

knightfly · Post by **knightfly** » Thu Aug 26, 2004 3:20 pm

Painting - marginal at best, except for a really porous material like block or brick.

Mud and tape really should be done each layer, because drywall is tapered along the long dimension, so that fasteners can be deep enough NOT to stick through the finish - in an inside drywall layer, NOT mudding these joints will leave a slight void (air pocket) along the length of the joint, which will slightly weaken the wall. I've not seen specs as to how MUCH this affects TL though - since it (sort of) starts to create an extra leaf in the wall at the void, I would think a slight loss in bass isolation with a slight improvement in midrange isolation would be what happens.

This must not be too serious, or Bryan would be noticing it; still, why take chances... Steve

z60611 · Post by **z60611** » Thu Aug 26, 2004 4:50 pm

Not mudding the first layer of a 20'x8' two layers of gypsum wall would leave an air space in the wall that is (8' + 8' + 20' + 20') x 4"x 1/4" = 672 cubic inches. The first thing I'd be worried about is that if there are any defects in any of the second layer, such as a bad tape or a popped screw that traverse any part of this 672 cubic inches, then suddenly you have an air channel to any air gaps or holes in the first layer. The first layer isn't mudded or taped, so it's got air gaps between the panels all over the place that this channel is guranteed to connect to. So basically by not mudding or taping, you've created holes through the wall. On average these holes would be 1/8" wide by the 4' + 8' + 4' border of the panels. So that's (20' + 8' + 8') * 1/8" = another 3 square feet of holes. At this point I'm not sure about the physics, but clearly the TL of the wall is limited by the second layer's taping and holes around the screws. The mass of the first layer may be acting, at least near the edges of the panels, more as a damping rather than a mass that the sound has to travel through. Also, on the borders of the second layer of drywall, covering that same 3 square feet of holes is only a thin layer of tape and mud, which has to be less TL.