6 Common Indian Sandstone Paving Problems [And How to Fix Them]

When it comes to landscaping, it’s no lie that Indian sandstone is a popular and effective choice of natural stone to use.

The variety of colour and choice of finish that Indian sandstone offers really can enhance your garden, whether it be for patios, pathways or outdoor dining.

That said, it doesn’t come without its problems. Below are the main problems you can have with Indian sandstone paving and how to fix them to keep your paving looking the part.

Common Problems with Indian Sandstone Paving

If you have any of the issues below, there may be fixes you can try yourself. However, if you’re struggling, it may be best to call a professional.

Voiding – uneven mortar spread underneath the Indian sandstone giving a ‘stained’ appearance 

Cracking due to butt jointing  

Delamination 

Green staining due to algae 

Yellow or red staining due to moisture absorption 

Uneven or bumpy surface due to incorrect placing 

Voiding Between Paving Staining Indian Sandstone 

Indian sandstone is laid upon a mortar mix of sand and cement, upon which the mortar base should be evenly spread out and flat.

Sometimes, landscapers use the ‘dot and dab’ method instead of evenly spreading the mortar, meaning there are gaps (or ‘voids’) underneath the paving that can trap moisture or water.

This will cause reflective staining on the sandstone paving to give it a dotted stained appearance. 

How to Fix 

• Before taking them up, try a basic clean using soapy water with a light power wash to temporarily remove the stains.
• To ensure the stains won’t come back, take note of affected tiles and gently take them up using a specialised paving tool or screwdriver, taking extra care not to damage tiles. 
• Observe the mortar to see if it looks like it has been ‘dot and dabbed’. If so, apply fresh mortar mix and evenly spread it out. Appropriate mortar mix for Indian sandstone paving is 4 parts sand to 1 part cement, slightly damp. 
• Reinstall slabs onto new base and seal. 
• If all your tiles are stained, its worth contacting the landscaper who carried out the job to have a good complain – this isn’t how they should have installed it! 

Cracking Due to Butt Jointing 

Cracks in your Indian sandstone could be present for a couple of reasons, but ‘butt jointing’ will be the most likely cause.

Butt jointing is the name given when paving slabs are installed too close together and ‘butt up’ against each other.

Indian sandstone paving slabs should be placed 8-10mm apart, as this gap allows for the slabs expanding when any changes in temperature or weathering occur.

If this gap isn’t left, they can impact against each other and crack, ruining your paving effect. 

How to Fix 

Unfortunately, this can be difficult to fix, but it isn’t impossible: 

• Remove any debris from the cracks you want to fix with a small brush or outdoor vacuum.
• Buy a resin jointing compound suitable for natural stone, which is also suitable for porous stone, such as Toupret Murex or Sika Fastfix.
• Using a scraping tool, gently fill the cracks and remove excess filler and allow at least 24h to dry. 
• If your Indian sandstone paving slabs are all too close too each other and keep cracking, contact the landscaper that placed them. 

Delamination of Indian Sandstone Paving 

Since Indian sandstone paving is completely natural, its unfortunately vulnerable to weathering no matter how hard you try to care for it.

One aspect of Indian sandstone weathering is delamination, the general term given to the flaking or ‘spalling’ of natural stone.

This happens with Indian sandstone when too much moisture content gets within the pores of the paving, which results in crystallisation and freezing action, eventually weakening the paving. 

How to Fix 

Natural weathering will affect your Indian sandstone over time, but there are a couple of precautions you can take to reduce the rate of delamination:

• Try and keep your sandstone dry – avoid unnecessary chemicals or washing often.
• If you do wash your sandstone, make sure to do it lightly, as pressure will weaken the integrity of your sandstone further – a powerful water wash on Indian sandstone is a big no! 
• Following on from this, avoid aggressive cleaning – unnecessary pressure will weaken your sandstone. 
• Sealing your sandstone can help, but avoid sealers or fillers with high water content, as this will increase moisture penetration within the sandstone. 

Green Staining Due to Algae Growth

Algae growth on your Indian sandstone paving is another natural aspect of sandstone, as natural stone is perfect for harbouring and growing many algae species.

Wet or moist paving result in rapid growth of algae which then thrive of the moist conditions, and this is difficult to avoid.

It might be natural, but it can be fixed too. As well as this, you can reduce the rate of algae growth too, meaning you shouldn’t have to worry about it too much in the future. 

How to Fix 

• Remove any heavy algae with a scraping tool, taking care not to scratch the stone too much. 
• Carry out a full, light-pressure clean of your Indian sandstone paving with a power washer. Instead of using any chemical cleaning treatment straight away, use warm, soapy water. 
• Once this is done and the sandstone paving is dry, re-clean but this time use a light bleach mixture (this can easily be done by making sure the solution is 30-40% bleach and the rest water). 
• Leave the mixture to sit for half an hour to an hour and gently scrub areas that are heavily affected with a sponge. 
• Wash away the bleach solution after this time with water to prevent discolouration. Repeat this every few months to prevent build up. 

Yellow or Red Staining Due to Moisture Absorption 

As you will now know, the key difference with sandstone compared to a lot of natural stone is that it is highly porous, meaning that moisture can lead to a few problems.

One of the key problems caused by moisture is either yellow or red staining, which is due to high moisture content driving iron oxidation within the sandstone.

When these iron minerals oxidise in the sandstone, they start to absorb into the stone itself, resulting in visible coloured stains (usually yellow, but red too when the stones iron content is high). 

How to Fix

• Firstly, avoid bleach cleans or high pressure cleans, as this can worsen your sandstone and bleach can react with rust. 
• Buy low percentage (<10%) hydrogen peroxide solution and pour over areas that are stained, making sure not to flood the area. 
• Gently rub the hydrogen peroxide into the stains with a spare paint brush or something similar (as long as it isn’t rough or sharp). 
• Let it sit for a day or two and then rinse. 
• If you want to go the extra mile or if your stains are really bad, acquire some acid-free rust remover that is suitable for Indian sandstone. This can be costly but can be effective too. 
• You can also try applying sealer, but this will struggle to get rid of the stains. It will, however, likely reduce the amount of staining in future. 

Bumpy or Uneven Indian Sandstone From Incorrect Placing

This is very much an issue caused by your contractors if it is the case, but incorrect placing of your Indian sandstone paving can cause it to become uneven or bumpy over time.

This can happen when some slabs are not placed the right way up, as the side that will face upwards will be a lot smoother ad better-finished than the underside will be.

So, if you notice that some slabs are uneven or bumpy then its likely they are not placed the right way up. 

How to Fix 

This can be difficult if your entire area is bumpy or uneven, but if its just a few, you can sort it yourself:

• Carefully try and see within the cracks to double check your Indian sandstone pave is the wrong way up first – there’s no point taking it up if not. Check whether it is the right way up with the image below. 
• If so, use a chisel or a similar tool to carefully bring the slab up. 
• Clean the slab with a light jet wash followed by a gentle sponge wash with diluted bleach solution and allow it to dry. 
• Using adhesive suitable for natural stone, replace the slab into its slot and leave it to set, making sure to apply some sealer 24 hours after. 

FAQ

When it comes to Indian sandstone paving, there are still some common questions people have, so we’ve answered a few of them for you with our professional opinion: 

Should I Seal my Indian sandstone to Avoid These Issues? 

Sealing can help with issues such as staining or cracking, but not always.

Moisture will find it difficult to get into sealed Indian sandstone once its sealed, but it also means it can trap it and cause more issues. If you’ve just got yours laid, it’s best to seal it, but not if its been around a few years. 

Is Jet Washing Actually Okay for Indian Sandstone? 

Not on high pressure no, as this can weaken the sandstones integrity.

A light wash can be beneficial, however, especially for rinsing away any products you apply. 

Will Bleach Damage the Stone over Time? 

If it is used often and in high concentrations then yes it most likely will.

However, if it is used in diluted form, for occasional cleans, and rinsed off thoroughly, then damage can be avoided.

Bleach is also excellent for other Indian sandstone problems as discussed above.