You have enjoyed many summers of fun in and out of your inground concrete pool but now the pool has aged and needs some repairs to the plaster lining. Plaster can become stained, etched, pitted, chipped or cracked over time but what can you do about it? Learn how to repair swimming pool plaster and whether you need to re-plaster the whole pool or repair those chips and cracks.
Damage to plaster can be repaired by the average home handyman. If there are only a few small chips or cracks in the plaster lining it makes sense to repair them before they get worse. You can repair these problems without draining the water by using waterproof plaster or marine epoxy compounds.
If the pool has several damaged spots and hollows under the plaster surface you will need to drain the pool to fix these problems.
If much of the pool is stained, cracked, chipped, etched, hollow or flaking you will probably need to completely re-plaster the whole pool which is a job best left to professional pool builders.
Table of Contents
What is Pool Plaster?
Concrete swimming pools are built with a concrete and reinforced steel shell about 30 to 45cm thick and are commonly lined with a white plaster to waterproof and finish the inside of the pool.
The plaster is usually a mixture of white cement and fine white limestone sand with a small amount of calcium to accelerate the drying process.
The plaster is white and the pool will look light blue when filled with water. Some people have a color additive mixed into the plaster to give the pool a deeper blue or a custom color.
What causes cracks in pool plaster?
Are cracks in pool plaster normal?
Yes small hairline cracks in pool plaster are normal due to the expansion and contraction of the pool surface which is caused by the water heating and cooling with the changing seasons. Larger cracks are not normal and indicate a more serious problem.
Can you patch & repair swimming pool plaster?
If there is a bad patch of plaster that has stained, etched or cracked you can chip it out and replaster the site. If the site is near the surface or in the shallow end you should be able to perform the task without draining the pool or maybe draining the pool down to the bottom of the skimmer box.
Purchase a plaster mixture that works underwater so that you can work it into the site and it will set in the water.
How do I fix a crack in my pool plaster?
You can repair swimming pool plaster cracks yourself.
Cracks need to be chipped out for the entire length of the crack and filled with new plaster. If there are many cracks or the cracks are large you will need to drain the pool so you can work the site.
How Long Does Plaster Last in a Swimming Pool?
Typically a plaster lined swimming pool will last 10 to 20 years depending on usage and how the pool has been looked after. Over time plaster will lose its clean, white appearance and build up a dullness and accumulate etches, pitting or stains. Most people realise and accept this is the normal aging of the pool surface but other pool owners want their pool to look great all the time so they choose to have the pool renovated more frequently. Hotels, apartments and other community properties will more frequently renovate their pools to uphold their high standards of maintenance and presentation.
How often should I Replaster my Pool?
This is entirely up to you and depends on the condition of your pool. All materials, including plaster, will deteriorate and show signs of wear as they age. On average, you should get 15 years usage from a plaster lined pool before you need to renovate it. If you have neglected your pool for a few years and it has had a few algae blooms, unbalanced water chemistry or other issues maybe it needs replastering sooner.
If you are planning to sell your home then replastering an old pool may add extra value to the house or at least make it more presentable for sale.
Should I Paint or Replaster my Pool?
The decision to paint or replaster your pool is a personal and financial choice. Painting will be the least expensive option but will last less than a new plaster lining. All pools need maintenance and eventually renovation so if you don’t want to have to paint the pool again in the future I recommend replastering it. With paint you will be repainting every 5 to 10 years but with plaster you will replaster every 10 to 20 years depending on how you have looked after your pool.
Can you paint over a plaster pool?
Yes you can. This is a common practice to rejuvenate the pool surface and change the color if desired. The plaster needs to be properly cleaned and prepared for painting to ensure the paint lasts the distance.
Do I have to acid wash my pool before painting?
Yes. Your pool surfaces must be clean, flat and dry so that pool paint will adhere to the plaster. I highly recommend an acid wash to remove all dust and dirt before painting.
Some people recommend lightly sanding the plaster surface to remove the polished smoothness which gives the paint better adhesion. Make sure you wash the surface afterwards to remove the dust. Please wear a mask when you do this to prevent breathing in the fine plaster dust particles.
Polish to Repair Swimming Pool Plaster
The option which I prefer is to polish the plaster surface instead of painting. If your plaster is still reasonably thick and in good condition but just has some staining, spots, pitting or hairline cracking you can use an angle grinder with a fine fibreglass flap disk to polish the plaster back to new again.
The grinding disk will remove a fraction of a millimeter of plaster to remove stains, dullness and any other minor imperfections to bring new life back into your pool. Wear a mask and wash down the pool to clean out the dust before refilling. This is the cheapest and easiest option that will give you at least another 5 years of usage before further renovation.
Fibreglass over Plaster
Another option is to have the pool lined with fibreglass over the old plaster. I had this done to one of my pools and it was very successful and looked great.
There are a few products available with brand names such as “Duraglaze”, “Fibreglaze”, etc. that are a fibreglass reinforced polyester laminate resin coating that is sprayed onto the plaster surface to transform your pool into new looking fibreglass pool.
This fibreglass coating has the following benefits:
- Non-porous so that stains cannot penetrate the surface.
- Resists algae which cannot deteriorate the surface.
- Smooth, non-abrasive and gentle on your skin.
- Makes balancing water chemistry easier as the lining does not react with water.
- Comes in a color range.
- Long lasting – 15 to 20 years before renovation.
- Comes with a 3 or 5 year warranty
How to Repair Plaster in an Empty Swimming Pool
If you have many cracks or weaknesses in the pool surface that you want to repair you will be better off draining or partially draining the pool.
Once you have drained your swimming pool the task is much easier but remember to be careful in the pool. It’s easy to slip and fall over or damage the pool surface.
The other thing to remember is summer is not the best time to empty a pool and replaster it because the plaster will dry very quickly leading to cracking. Wait until the fall or winter.
Check the Pool Surface
Firstly, you need to check the condition of the pool surface by visually inspecting the plaster. Use a marker pen to mark any damaged plaster that you want to repair. Don’t worry the mark can be sanded away if you don’t repair the site.
Next take the handle of a hammer or a piece of smooth wood and gently tap over the whole plaster surface to find any hollows. You will hear a hollow sound indicating there is a gap between the plaster and concrete shell. This is more common on the bottom surface but can also occur in the walls. Mark these hollow sections.
Usually you would want to chip out the plaster on the hollows and refill with new plaster. However, I have seen pools where the hollows are small and have been left alone. When the pool was full these hollow sites didn’t crack or cause any problems so it’s ok to leave them and refill the pool.
Chip Out the Repair Sites
After you have marked the pool where you want to make repairs chip out the sites with a chisel or small hammer power tool. Make the edges of the sites vertical and sharp not angled and smooth. This will help the plaster fill the gap and bond to the surrounding plaster. Please wear safety clothes, gloves, mask and eye protection.
Clean the Repair Sites
The chiseling process will cause lots of debris and dust in your pool. Sweep it down to the lowest part of the pool and clean it out. You can use your vacuum cleaner to vacuum each repair site to thoroughly clean it of dust. Next wash the repair sites and allow to dry.
Polishing the Pool Surface
I highly recommend you polish the pool plaster while you have the pool empty.
An extra process you can do is to polish the whole pool surface to make the plaster clean, smooth and white again. This is a simple process but works wonders on plaster pools to make them look new again.
Use an angle grinder with a fibreglass flap disk. These disks are designed to cut down fibreglass and come in different grades of coarseness. Buy a fine grade as we only want to polish and not cut into the plaster. Gently run the grinder over the pool surface to polish up the surface. This process will clean away any marks, stains, pitting, scaring or dullness in the plaster surface. The process is very dusty and takes hours of work but the results are worth it.
Please wear safety clothes, gloves, mask and eye protection. You may want to run a vacuum cleaner while grinding to capture most of the dust.
Mix the Plaster
Mix the plaster product according to the manufacturer’s instructions. You want the product to be a thick paste consistency that is easy to spread and stays in place.
Fill the Repair Sites
Spray the repair site with water as the plaster will stick better to a damp site. Spread the plaster over the site with a trowel making sure it’s firmly in the site with no bubbles under the plaster. If you have many repair sites you need to work fast because the plaster dries quickly.
You can respray each repair site with water if necessary to keep them from drying too quickly. If the repairs dry out quickly they may show signs of cracking.
As soon as you have finished the repairs you need to refill the pool as plaster cures better underwater than in air. Also the water exerts pressure on the plaster to keep it in place while curing and hardening.
Refill the Pool
Start filling the pool with the garden hose or truck in the water to more quickly fill the pool. As you fill the pool keep your repair sites damp with a spray bottle until the water reaches the sites. Once the water has filled over the repair the water will hold the repair in place and allow it to cure slowly.
How to Repair Plaster in a Full Swimming Pool
If you only have some minor chips, cracks or flaking in the plaster nearer the surface of the pool then you may get away with not draining the water.
You will need a mask and snorkel to see underwater. Chip out the damaged plaster and refill with new plaster. Follow the instructions as for repairing an emptied pool to chip out the damaged plaster. The plaster will fall to the bottom and needs to be vacuumed later.
There are two options as to what material you use to make the repair.
Plaster
Buy the waterproof plaster for use underwater. Mix up a batch following the manufacturer’s instructions on the label and patch the repair sites.
Marine Epoxy
Please wear protective gloves and glasses.
The best product comes with two strips of putty-like material that you mix together to form the patching compound. Once mixed it will dry rock hard very quickly so work fast to fill the holes or cracks and smooth it off with a trowel. You normally only have 10 minutes maximum before it begins to set hard. After a few hours it will be rock solid.
Please read our article on How to resurface the swimming pool
Conclusion
The average home handyman can successfully repair swimming pool plaster surfaces when there are only a few small chips and cracks. This will save you considerable money and lengthen the lifetime of your pool.
If your pool is old and has significant damage to the plaster lining. Call in the professionals to replaster the whole pool.
Your pool is a large investment and part of your home. Renovating the pool will maintain the value of your property.
