Preparation of existing painted drywa...

Log Out | Topics | Search Moderators | Register | Edit Profile

Author Message Trevor Senior Member Username: trevorpan Post Number: 17 Registered: 04-2014 Posted on Saturday, July 09, 2016 - 12:39 pm:    Hi, I have a small bath remodel. All existing tile will be removed. The portion above the existing wainscot is a painted. What is the best way to prep this painted area for bonding? Sanding, chemical? Thank you, Trevor Trevor Pan http://www.trevorpan.com John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1677 Registered: 03-2002 Posted on Saturday, July 09, 2016 - 03:32 pm:    I'm not sure I understand exactly what you anticipate doing. Are planning to paint drywall that has had existing tile removed? Or, are you planning to install tile on existing painted drywall? (Or something else?) Trevor Senior Member Username: trevorpan Post Number: 18 Registered: 04-2014 Posted on Saturday, July 09, 2016 - 09:21 pm:    Hi John, Thank you much for replying. Pardon me for not being more clear. The enclosed rendering is what I want the final design to look like. I just want to ensure I'm getting the best bond of thinset to the existing drywall which has a semi gloss paint. Maybe it just needs to be cleaned with TSP or something? Thank you, Trevor Pan http://www.trevorpan.com Michael Chusid, RA FCSI CCS Senior Member Username: michael_chusid Post Number: 171 Registered: 10-2003 Posted on Saturday, July 09, 2016 - 10:55 pm:    If existing tile is being removed, and perhaps plumbing/lighting/cabinets ripped out, you will have lots of damaged surfaces to replace. Why not take the finishes down to the framing and and apply new backer board. Michael Chusid, RA FCSI CCS www.chusid.com www.buildingproduct.guru Trevor Senior Member Username: trevorpan Post Number: 19 Registered: 04-2014 Posted on Sunday, July 10, 2016 - 11:02 am:    Hi Michael, I have thought of that. Maybe it's better to just gut the whole thing. In that case I was planning on cement board at shower, and water resistant gyp board elsewhere. Now, in cases where it's not necessary to remove wall board, would you say its inadvisable to adhere new tile to a painted surface? My concern was the weight could peel the paint away. Wouldn't want to experience that fun call. however, there may be a way to do it I'm ignorant to. Thank you, Trevor Pan http://www.trevorpan.com Michael Chusid, RA FCSI CCS Senior Member Username: michael_chusid Post Number: 172 Registered: 10-2003 Posted on Sunday, July 10, 2016 - 02:44 pm:    Perhaps questions will help you arrive at conclusion. -Do you know if the existing drywall and joint treatments are water resistant types? -Any evidence of nail popping? - Are there multiple layers of paint? - Does the paint resist scraping with a knife? - Pull off by adhesive tape? - Is the wall flat enough to receive the large format tiles shown in rendering? - Is paint glossy? - Is it a lead-based paint? I have no good (no-good) answers: Since it is a small room, the time spent sanding and cleaning the painted surface is small; possibly less than the time to definitively answer your question. You will need to clean surfaces anyway due to demolition dust. Finally, consider applying wire mesh and a thick-set mortar base... You will have no difficulty bonding the tile to that. ;-) Michael Chusid, RA FCSI CCS www.chusid.com www.buildingproduct.guru Trevor Senior Member Username: trevorpan Post Number: 20 Registered: 04-2014 Posted on Sunday, July 10, 2016 - 03:50 pm:    These things are like an enigma ` I think I'll use the thick set at contractor's option, but tend towards ripping it all out and starting fresh. Thank you for the thoughts Michael - and super cool work on Caesarstone USA - Trevor Pan http://www.trevorpan.com Dave Metzger Senior Member Username: davemetzger Post Number: 648 Registered: 07-2001 Posted on Sunday, July 10, 2016 - 10:43 pm:    A related issue is not to forget the relationship of the existing switch boxes, outlet boxes, and door and window casings to the face of wall finish, i.e. the plane of the new tile. If the tile will project beyond the plane of the existing gypsum board, or the plane of the existing tile (especially if the new tile is mud-set), then the electrical boxes will need to be relocated within the thickness of the wall, so that switches, switch plates, and light fixtures will be mounted properly. Dewayne Dean Senior Member Username: ddean Post Number: 64 Registered: 02-2016 Posted on Monday, July 11, 2016 - 10:18 am:    I think there are extensions that can be added to electrical boxes that can be used after the wall plane is changed. Guest (Unregistered Guest) Unregistered guest Posted on Monday, July 11, 2016 - 11:02 am:    Contact the manufacturer of your tile setting mortar for proper preparation of substrates. They will be able to tell you what should be done for the painted gypsum board. J. Peter Jordan Senior Member Username: jpjordan Post Number: 901 Registered: 05-2004 Posted on Monday, July 11, 2016 - 11:16 am:    A reputable tile installer will probably recommend using cement backer board and thinset mortar rather than a mortar bed. You can install this over the existing drywall in 1/4- or 3/8-inch thickness of cement backer board. This gets you around any incompatibility with the existing finish. If you decide to remove the drywall, use 1/2- or 5/8-inch cement backer board. J. Peter Jordan, FCSI, AIA, CCS, LEED AP, SCIP John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1678 Registered: 03-2002 Posted on Monday, July 11, 2016 - 11:23 am:    If you were going to adhere tile over painted drywall, I think that as long as the drywall is in good condition, and the glossy paint is lightly sanded, and thoroughly cleaned with TSP (and rinsed of TSP residue) you could adhere to it without too much difficulty. But, is the small savings in time and cost worth it? Unless a lot of drywall remains, it seems like it would be just as economical to remove the existing, and you'd have better quality. I've done a lot of remodeling myself over the years, both on my own house and as a contractor. My rule of thumb is that "saving" construction in place in an effort to save time or money is unlikely to actually do so. There so much fussiness: as pointed out above, maybe the new and old materials won't be flush; you have to do special prep work; you find out you need to do a lot of patching that's almost as time consuming as replacement; you realize less work can be saved than at first thought; you go to extra effort to save work in place, then need to tear it out for an unanticipated reason; etc. The list of pitfalls is long. Usually, starting with a clean slate saves effort. Dave Metzger Senior Member Username: davemetzger Post Number: 649 Registered: 07-2001 Posted on Monday, July 11, 2016 - 11:44 am:    John's nailed it. The older I've gotten, the more I've realized how much the KISS principle applies. Dale Roberts CSI, CCPR, CTC, LEED Green Associate Senior Member Username: dale_roberts_csi Post Number: 123 Registered: 10-2005 Posted on Monday, July 11, 2016 - 12:08 pm:    In looking at rendering, it appears to be a large format tile? In the wet area I would definitely recommend cement backer board or mortar bed (think scratch and brown coat). If this is under 8 x 8 you can bond the tile directly to the gyp board. In that case I would recommend either scarify the substrate or if it is sound and intact use one of the manufacturer’s multi surface bonding primers. If this is a large format heavy tile then you have to ask can the gyp hold the weight of this material up without delaminating. It most cases you would be ok, but it is definitely not the best substrate. I would recommend R&R and again either Cement Backer Board or mortar bed would be appropriate. If you want specific product recommendations and a detail please email me. DaleRo@CBPmail.net Sheldon Wolfe Senior Member Username: sheldon_wolfe Post Number: 919 Registered: 01-2003 Posted on Monday, July 11, 2016 - 04:31 pm:    I love discussions like this; they remind us how difficult construction - and our jobs - can be. You start with what appears to be a simple task, it quickly becomes a long list of questions, then moves on to a discussion of options, seasoned with sage advice. Yet most of our non-specifier peers think what we do is boring! Trevor Senior Member Username: trevorpan Post Number: 21 Registered: 04-2014 Posted on Monday, July 11, 2016 - 05:32 pm:    Wow, thank you all for some more insights. I had asked a drywall manufacturer, they said that 5/8" can hold 6-8lbs sf. So, I thought we'd be ok on the wall. At the shower, I've got 1/4" cement board, maybe ought to thicken that up to 1/2" as mentioned. I'll keep you posted on how it goes. May end up costing too much, and have to go with a wainscot... Which leads me to a BIM question. Does anyone use a cost spreadsheet with their models? Have been looking into quantifying materials as the model is produced... that way I know from a dollar standpoint where the project is. Just starting out. Trevor Pan http://www.trevorpan.com Dale Roberts CSI, CCPR, CTC, LEED Green Associate Senior Member Username: dale_roberts_csi Post Number: 124 Registered: 10-2005 Posted on Monday, July 11, 2016 - 06:15 pm:    Hi Trevor, ¼” Cement Backer Units (CBU) can go over solid backing. ½” CBU can go over open framing. Most direct bond tile installations weigh 5 lbs. to 7 lbs. per S.F John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1679 Registered: 03-2002 Posted on Tuesday, July 12, 2016 - 04:12 pm:    Be wary of costing based on very small projects like a bathroom. Usually, only one mechanic fits at a time inside, meaning inefficient crews; there's no economy of scale, it may actually be the reverse if the work of one trade takes only part of a day; and scheduling is hard, for both of the reasons just mentioned. I would simply ask some quality general contractors what a gut remodel bathroom takes in their area. Here in the Boston area (I've got one of these myself that I'm starting to plan), a gut remodel bath is in the high twenty- to low-thirty thousand dollar range. We are in one of the highest cost US markets here, so hopefully you can do it for less than that.