How to prepare interior walls for smooth finish?

[Gus241]

Hi guys,

I've been crawling through previous posts but haven't been able to find the answer relevant to my inquiry.

I was hoping for some advice from the wise heads here regarding a cost-effective and efficient way to prep interior plaster walls for painting. The previous owners slapped on one or potentially two coats of paint on top of the previous paint, with minimal prep. You can see this through the paint in the form of way too many lumps, bumps, paintbrush marks, and dirt underneath the paint or present at key eye level.

Based on my research, I've tried skim coating with Gyprock's topping compound, and it's definitely given me the best results in terms of smoothness and workability. However, it's not the most cost-effective when you're trying to cover about 100 square meters of interior space, and it leaves a significant amount of mess to clean up, which the finance minister isn't overly happy about.

A friend of mine suggested sanding the walls with 180 grit paper first, followed by three coats of sandable acrylic undercoat, a final 240 grit paper sand, and then finishing up with the desired paint. This idea sounds good and easy to manage and clean up while tackling one or two walls prep every second day.

I'd love to hear your thoughts and see some photos for reference. The paint feels like sandpaper with a lot of grittiness. I totally understand that certain chips and holes will need filling and sanding regardless to achieve a smooth finish.

Thanks in advance

[Jason]

Welcome to Bunnings Workshop @Gus241.

You've come to the right place. We have loads of experienced renovators in the community who are passionate about sharing their projects and experiences. 

Let me tag some wonderful members to kick off the discussion for you:

@EleventhCoastal, @kendallmac, @OurSweetRetreat, @Acewoodhome, @sharnpaterson, @prettyliving, @Renowayoflife       

One of our resident Bunnings D.I.Y. experts will also be happy to assist as soon as possible.

Jason

[kendallmac]

Hi Gus,

Great question! The way I see it, you have 2 choices. You can persevere with learning all about topping compound and plastering methods (and let me assure you, you’ll need a few goes at it) or you could find a well referred Plasterer in your local area to set this for you. In my opinion, plastering is one of the hardest things to get right in a DIY campaign as the results are so visible and once you’ve painted, there’s no going back. 

Find someone who will give you a cash price up front and tell you how long it will take and what’s involved. Even if you need to spend a few months saving, it’s money well spent. Then you can paint those walls, knowing all you need to do is give everything a light sand before you start. 

Good luck!

Kendall 

[Gus241]

Thank you, Kendall for your response And a whole-heartedly agree with you. Unfortunately being based in Sydney and it is extremely difficult to find good  trades, let alone who could do tricky jobs like these.

Majority of the trades I've dealt with either are looking for straightforward jobs or they're going to charge you inconvenience costs in addition. It doesn't help when you are living in the house and have to move furniture for these guys. Using an example of a painter who want us to move all the furniture out of the house for him to paint the house, which I guess it's not going to happen.

Anyway, I will persevere and learn a new skillset which is one of my goals for this year. I think majority of the house i can get away with a good sand but I really want to try my hand on skim coating which has been pretty good but time consuming. 

If you were in my situation, and outsourcing the job to a plasterer is not possible. What will be the next step whilst balancing cost efficiency and effectiveness? 

Thanks again for your response. 

[OurSweetRetreat]

Hi Gus, 

I feel your pain! We live in a an older character home which has been subjected to many layers of paint over it's lifetime, including I suspect a quick paint job by our previous owners prior to them selling. 

I have painstakingly worked my way (still working my way) around our home and have resorted to sanding with 120 - 180 grit sandpaper first and of course patching any major defects where necessary. If you don't already have one, I'd recommend purchasing an Orbital Sander and Vaccum Attachment, I have an upmarket one with a hepa filter which I like to use especially for tasks inside, but for a budget friendly option the Ryobi Orbital Sander and Vaccum are both great and will help cut down the time of hand sanding and also limit the dust flying around your home. You will be surprised how smooth the walls will be with a light sand. You will obviously need to patch and sand any major defects but a light sand will definitely remove that sandpaper like finish and stroke marks you are talking about. Also when it comes to painting the right roller will leave somewhat of a uniform stipple like texture to the walls as well. And I'd recommend a low sheen paint for the walls (Dulux wash and Wear is great) and Semi Gloss Aquaenamel for the Trims. I just refresh our master bedroom window trims this week and a light Sand and two coats of the Aquaenamel and it's never looked better. I hope that's helpful. Regards, Danielle. 

[EricL]

Hi @Gus241 

My apologies for the late reply. I suggest investing in a Ryobi 300W Random Orbital Sander ROS300-S or similar larger tool used for sanding plasterboard walls. Using mechanical aids should reduce your sanding time and allow you to go faster. My best advice is to invest in the best possible roller your budget will allow you to. Make sure to clean the roller very well as any paint residue left on it will reflect on your wall surface. I also recommend investing in an Ozito 1250W 20L Wet And Dry Vacuum to greatly reduce the amount of sanding dust that you'll need to tidy up. 

Please remember to wear personal protection such as gloves, goggles and a 3M Medium Paint Project Reusable Half Facepiece Respirator.

If you need further assistance, please let us know.

Eric

[Gus241]

Hi guys! Thanks for for all the responses so far. Really appreciate your input in terms of tools. Majority of them are being used during the process.

I'm still interested to hear opinions regarding what would be the an efficient way out of these two techniques I'm trying to use:

- sand with 180grit, skim coat, followed by light sand with 240grit, primer and 2x top coat, Time consuming but has been providing the best results.(the progress photo attached)

Or 

Decent sand with 240grit, 2 to 3 coats of sandable primer, light sand in between followed by top coat.

I'm not expecting professional like results but at the same time if I can achieve 80% correction I'll be extremely happy with that.

 

[JacobZ · Accepted solution]

Hi @Gus241,

As the issue is more about the texture of the existing paint than it is about knicks, depressions or holes in the wall, skim coating might not be required. 

As you have already seen, skim coating the walls will definitely give you a good result, and you can always go back to that approach if you are not getting the desired result, but it might be more than what is necessary. If there was a small section you could test on, I would give the second approach a try and see what you think.

Having worked with a number of painters and plasterers, the main thing you need to focus on is sanding between coats. Whether it is plaster, primer or paint, a light sand to ensure the surface is flat will make the next layer look much better. Use a pole sanding tool such as this Rocket 230mm Giant Sanding Tool or Hyde 225mm Radial Sander Plaster Tool. If you were happy to spend a bit more money, this Full Boar 750W 225mm Drywall Sander, which can be directly connected to a wet and dry vac or dust extractor to keep the dust down, would be even better. Trust me, they make things so much easier in terms of both efficiency and wear and tear on your body. 

I would start by giving the existing paint a sand with 180-grit before applying the primer. 

Once sanded, apply a coat of primer, allow it to dry for the recommended recoat time, then give it a light sand with 240-grit. At this point, you can assess the flatness of the wall. If you are not happy, add a second coat of primer.

Once the primer is dry, give it another quick sand with 240-grit before applying your paint.

I think this approach would yield a fantastic result, but if you are not happy with it, you can always go back to the skim coating approach.

Let me know what you think.

Jacob   

[Gus241]

Thank you, Jacob, great advice!
Bit of an update - Tried this approach on a small area, and results are fantastic given the time being spent. I used 14mm nap for primer application, and then utilised 10mm for paint application. However some wall will require a skim coat due to major indents - do you have any suggestion for a topping compound in bigger bucket appropriate for skim coating? 

Thank you again. 

[EricL]

Hello @Gus241 

I propose looking at the Gyprock CSR 15kg Easy-Finish Topping Compound and the Gyprock 15kg Gold Topping Compound. I suggest downloading the Residential Installation Guide from the Gyprock website. 

If you need further assistance, please let us know.

Eric