Are you planning a house renovation and struggling with deteriorated lime mortar? We share our experience with lime mortaring and provide essential knowledge for DIY renovators like you.
Our guide covers the entire process, including important steps like wall clearing, render removal, stone or brick raking, and applying the mortar mixture. We emphasize the significance of breathable walls and the dangers of poor rendering or cement patches that can trap moisture and create serious damp issues.
We cover everything from costs to tips on lime mortaring. You’ll learn about the importance of proper materials and location-specific considerations that can extend the lifespan of lime mortar to over 50 years. We’ll also share our DIY knowledge and recommend a lime mortaring course for those who want to dive deeper into the subject.
Weather conditions and the curing process of lime mortar are essential aspects to consider. We’ll discuss the best practices for curing, such as hessian wrapping and proper moisture levels. We also provide tips for achieving a flat finish and maintaining the overall aesthetic of your walls, including techniques like sponging down, tapping down, and wire brushing.
- Did Our House Need Re-Mortaring?
- Could we Do It Ourselves?
- Choosing the right Materials
- Scaffolding and Site Accessibility
- Removing the Render
- Disposing of the Rubble
- Raking Out
- Examining the condition of the Stonework
- Waiting for a Weather Window
- Hessian or polythene Wrap?
- Mixing the Materials
- Wetting Down the Wall
- Applying the Mortar
- Sponging down or Tapping Down?
- Wire Brushing
- Hydrochloric Acid Wash
Did Our House Need Re-Mortaring?
Let’s start with determining if your house needs re-mortaring. Signs to look out for include crumbling mortar, insect ingress, damaged bricks or stones, cracks, wet bricks or stones, and efflorescence – that white powdery substance. In our case, we had ignored our mortar problem for too long, resulting in loose stones and noticeable cracks. It was clear that quick action was needed before our house value took a major hit.
Now, let’s talk about the impact of deteriorated mortar on the market value of your house. An experienced estate agent could easily spot the deteriorating mortar and how it negatively affects the overall appearance and structural stability of your property. Taking care of this issue is crucial if you want to maintain or even increase your house value.
Could We Do It Ourselves?
When we moved to France, our house was in desperate need of renovation. But without any tools, DIY knowledge, or understanding of what a well-maintained wall should look like, we were overwhelmed. Fortunately, our friends Lesa and Ted from Château de Montmagner were already lime mortaring experts, and they were kind enough to teach us the ropes through their course.
Our house had serious damp problems, largely due to the use of cement in previous renovations over 50 years ago. This led to cracked stones, water ingress, and a significant drop in market value. The poorly applied rendering only worsened the dampness. It was clear that re-mortaring was necessary to restore the house to its former glory.
Getting the mortaring right is crucial, as it can last for 50 years or more. However, if done incorrectly, it can leave the house in an even worse state than before. That’s why attending a lime mortaring course was invaluable for us. We gained a deep understanding of the importance of proper mortaring techniques and how it would impact the long-term durability of our walls.
It’s crucial to inspect the deteriorated mortar and assessing the overall damage and every job will kick up surprises many of which will be hidden until the mortar is removed.
If you get mortaring wrong, you can cause damp issues, cracks and make your house unsightly. Obviously, this will devalue a property and may require it to be re-mortared from scratch.
Choosing the Right Materials
One of the key considerations when using lime mortar is choosing the right color to match the exterior of your house. We’ll discuss different options for achieving the perfect color match and suggest alternatives to gray, such as NHL 3.5 blanche or white, which can offer a more sympathetic look.
In the past, tinting mortars involved adding clays, ash, and even spices like turmeric. However, nowadays, there are convenient jars of silicon-based colorants available that are less likely to discolor over time. We’ll explore these modern options and help you make an informed decision.
If your house has been subjected to poor renovation practices by cowboy builders, you may have encountered patches of cement on your walls. We’ll explain the importance of meticulously removing these patches, as they can have a visible impact on the interior of your house, even if the walls are thick.
Old houses often lack a damp course, requiring breathable walls. Cement patches on your walls can effectively strangle the house, leading to damp problems and other issues. We’ll delve into the significance of breathable walls and provide insights on how to create an environment where your house can “breathe.”
To further understand the three strength grades of natural hydraulic lime: NHL2, NHL3.5, and NHL5 set out in the European Norm EN459 talk to a professional. It could avoid serious damp issues and poor rendering outcomes.
Scaffolding and Site Accessibility
Let’s address the challenges of renovating an old house on a sloping site with moisture issues. Our site, for example, is situated on a slope, plus the soil can be moist due to surrounding springs and wells. This can pose serious damp problems for the house, requiring special attention during the renovation process.
The road leading to the house is extremely narrow and the area is best described as extremely rural.
One crucial aspect to consider is scaffolding. In our case, the fixed scaffolding available in DIY stores wasn’t suitable due to the slope and overhanging structure. We explore the option of hiring scaffolding, which currently costs around €20-30 per m² / per month. Considering the size of our house (12.5 meters wide and 6.5 meters tall), the estimated cost for scaffolding comes to €2,437.50. Fortunately, we had friends with a 5-meter tall tower, which saved us some expenses.
The ideal situation is to have the entire fascia of the property, or indeed the entire house covered in scaffolding. This is particularly true when using hessian or polythene wrap or when passing pedestrians need protecting from falling debris; after all you don’t want to close a road or have someone hurt.
When starting the renovation, it’s important to clear the area around the wall of any pot plants, benches, or debris that might hinder the progress. While our wall didn’t have ivy or vines trailing over it, many houses in France do, and clearing them can significantly impact the project’s cost. Additionally, dealing with ivy ingress during the raking-out process can slow down the renovation progress substantially.
Power lines, incoming internet, damaged guttering, chimney stacks, fences, trees, nesting birds, property boundaries and other obstacles can all cause problems and additional costs.
Removing the Render
The exterior of our old house had a coarse rendered or Crépi finish, which had started to detach and trap moisture. This not only caused serious damp issues but also provided an entry point for insects and lizards. It was an eyesore and significantly devalued the house. Removing the deteriorated mortar became a priority to restore the house’s market value and address the damp problems.
When it came to removing the render, we opted for a cost-effective approach. No power tools were needed; a simple spiked hammer from a Brocante did the trick. It’s good to know that you don’t always have to invest in expensive equipment.
While the typical removal costs for render range between €25 and €60 per m², the actual expenses may vary depending on factors such as the condition of the render and the underlying brick or stonework. If you’re dealing with brick surfaces, the process is usually easier than with stone, as power tools can be used and the render might come off in sheets, simplifying the removal process.
70m² x 60€ per m² = €4,200
We took around 45 minutes per m² to remove the render.
(NB. We used hand tools and it was very deteriorated)
If you’re considering lime mortaring as an alternative to lime rendering, it’s important to understand the benefits. Lime mortar allows for breathable walls, preventing moisture from being trapped, and allowing the walls the breathe more easily. Additionally, lime mortar can be color-matched to the exterior, maintaining the original aesthetic while offering a durable solution.
If you are considering re-applying a lime-render it is important to understand that you may still need to re-mortar first. The lime render can finally be applied with a modern spray gun.
Disposing of the Rubble
One of the first things to consider is the removal of rubble and waste disposal. In our case, we had to make multiple trips to the recycling center due to the amount of debris generated.
Cost considerations are also important when it comes to mortaring. While some quotes may include clean-up, others might not, so it’s essential to factor in potential additional costs.
We were fortunate enough to have a van with a tow bar, but keep in mind that skips may not be readily available in all areas. It’s important to factor in the cost and labor involved in this clean-up process, as it can be a significant addition to your renovation bill.
In addition to general waste disposal, there may be specific items that require special handling. For example, we had an asbestos chimney outlet that needed to be removed. While our recycling center provided free special sacks for this purpose, it’s worth noting that in other areas, this type of waste disposal may come at an additional cost.
Check your quote covers waste disposal as although it often assumed, it be a hefty additional charge or a huge mess for you to clear up afterwards.
Raking Out
The first step in re-mortaring is the raking out process. While power tools like disc cutters and drills can be used on brickwork, we recommend using a hand-held spike or a hammer and chisel for stonework to prevent damage to the stones. In our case, the mortar was so soft that a stiff plastic brush was sufficient to sweep it out. We advise raking out to a depth of 15mm, but if the material remains nothing more than sand at this depth, consider going deeper. We also demonstrate the use of a compressor and air gun to blow loose aggregate out of the joints, ensuring a clean surface for further work.
One particular area of our wall was home to a nest of bees, luckily we’d had a professional remove the hive from the inside the previous year. We’d temporarily blocked the hole until we could begin re-mortaring. Bee’s, insects and lizards dig out the mortar and create nests. Some of these creatures need specialist removal. In the barn is a swallow’s nest. All this need taking into account.
Raking out the deteriorated mortar not only allows for a fresh start but also reveals the true condition of the wall. We share insights into how we discovered missing stones and identified areas where moisture and damp had penetrated, causing damage. By understanding the root cause of the damp, you can effectively address the issue to protect your walls in the long term.
Typically, the cost ranges from 25€ to 60€ per m², with brickwork being cheaper due to the use of power tools. However, when cement has been used on stonework, the cost may be closer to 60€ per square meter.
70m² x 60€ per m² = €4,200
We took around 45 minutes per m² to remove the lime mortar.
(NB. We used hand tools and it was extremely deteriorated)
Rooted Vegetation
Additionally, factors like weed and ivy ingress can significantly impact the cost and timeline of the project. If you’re dealing with serious weed or ivy ingress, it can cause extensive damage and delay the raking out process. We emphasize the need to address and remove any rooted vegetation before proceeding further. When ingress becomes an issue, there will be a knock-on effect throughout the restoration. Walls will be left unstable, more mortar will be needed, labour times will increase dramatically and costs will measurable increase. Often, damage can be so extensive, you are effectively rebuilding a wall from scratch.
Typical labour costs with rooted vegetation ingress 80€ to 120 per m²
We recommend working from top to bottom during raking out, but in our case, blowing loose aggregate out the joints using a compressor and air gun allowed us to perform it in a random manner. Raking out not only reveals the condition of the wall but also identifies missing stones and the sources of moisture and dampness.
We highlight the importance of checking if rubble disposal is included in the quote to avoid any surprise expenses.
Examining the condition of the Stonework
When embarking on a house renovation project, it is crucial to evaluate the condition of your stonework house. Years of cowboy builders and bodge repairs can lead to missing stones, damaged blocks, and long cracks that result in leaking gutters and mold caused by flooding. Cracks from a broken and previously repaired roof beam can also be present. In addition, you may discover holes caused by insects, lizards, and rodents, which become obvious once the mortar is removed.
Budgeting for replacement stones is essential, especially if they need to be sourced off-site as it can be time-consuming. Loose stones are also a common issue, which may require overnight re-insertion. However, it is important to note that once a house is “raked out” for re-mortaring, it becomes quite unstable, so precautions must be taken to avoid a collapse.
Ideally, re-mortaring should be done from the top down to prevent dropping mortar on your work. However, if your walls are particularly unstable, working bottom up may be necessary to alleviate extra weight.
With everything “raked out”, it is an ideal time to trace problems such as cluster fly ingress or drafts around windows.
There is absolutely no point in re-mortaring a house if you are not going to fix issues that caused mortaring problems such as leaking guttering or missing roof tiles. These issues can be addressed whilst the scaffolding is in place. Be prepared for additional costs and repairs found whilst examining the stonework.
Unexpected Costs
We had 12.5 meters of aluminium gutter needing replacing (material costs approx 350€), luckily we had a large stack of spare slate tiles. Three rows of roof tiles needed removal, new tiles had to be sourced and re-laid, joints soldered and checked for leaks bracket. Even the down pipes had to be drilled and bonded into granite stonework. This definitely wasn’t a job for the inexperienced or those scared of heights.
Typical aluminium gutter installation charge 40€ to 60€ per m. NB. Add broken tiles to this.
Typical installation for a 12.5 meter house would be would be €750.
Waiting for a Weather Window
Before you start the re-mortaring process, it’s crucial to consider the curing conditions for lime mortar. The optimum temperature range for curing lime mortar is 15-20°C, with a relative humidity of 55-85%. Additionally, you should avoid direct sunlight, rain, or frost during the first 72 hours after mortaring.
The minimum temperatures for lime mortaring is 5°C and the absolute maximum is 30°C.
Why is my mortar turning white?
When lime mortar is drying too fast it turns white.
To ensure proper curing, your lime mortar should be kept damp for a minimum of 10 days. This should be done over the weekends and holidays as well.
This prevents the mortar from turning white, as the lime is drawn to the surface during the carbonation process. You can achieve this by using a garden hose with a spray head or a handheld sprayer. However, be careful not to saturate the new work.
If you’re wondering when to undertake this project, spring and autumn are typically the best seasons for mortar work. In Central France, where we are located, summer temperatures can reach up to 45°C, while winter temperatures can drop to -10°C. It’s also important to note that lime mortar takes around 90 days to fully cure.
If you are employing professionals make note of holiday sessions, as walls may need regular attention during these periods.
Weather windows affect weather a wall needs to be wrapped, insulated, or maintained moist.
Hessian or polythene Wrap?
Wrapping a wall with dry hessian or polythene wrap helps to prevent frosts cracking, while it dries.
During the summer months use a hose with spray head to keep the area from drying too quickly.
Allow 110€ per + delivery per 46 meter x 72″ wide 8oz roll of hessian wrap.
Typical wrapping costs are €25 to €40 per m².
Mixing the Materials
Before getting started, you’ll need the right materials and equipment. Builders sand and lime mortar mix are the key ingredients for a successful project. You’ll also need a cement mixer, and while you can find affordable options starting around €250, it’s important to check if it’s hire included in any quotes you receive. Luckily, we already had our own.
Finding the correct mixture may require some trial and error, as it takes experience to achieve the desired consistency.
We are using a 3 to 1 mix (by volume).
3 Builders Sand (Orange in colour) – 25kg
1 Lime Mortar (Chaux Saint Astier NHL 3.5 pure blanche EN 459-1) – 25Kg
Check materials are included in quote.
For our 70m² wall we’ve used 6 sacks of Lime and 36 sacks of Builders Sand.
We are not using a colorant, although they are available from companies such as Sika.
The mixture should tumble correctly in the mixer and shape into a sticky dough ball-like structure in your hand.
Once you have everything you need, the next step is to mix the lime mortar. This process involves carefully measuring and combining the builders sand and lime mortar mix in the correct ratio. The mixture should be thoroughly blended using a cement mixer until it reaches the desired consistency.
Wetting Down the Wall
It’s important to understand the significance of keeping the walls damp during the mortaring process. This ensures decent mortar adhesion and prevents rapid drying. To achieve this, start by brushing down the walls to remove any loose aggregate. We use a compressor and air gun.
Then, grab a garden hose with a spray head or a handheld sprayer to keep the walls moist. It’s crucial to keep the hose nearby as Lime Mortaring takes time, and the walls will constantly need dampening down. Remember not to saturate the walls or the mixture.
Lime Mortaring
With your lime mortar ready, it’s time to start applying it to your walls. Whether you’re working with stone walls or brick walls, the process remains the same. Begin by filling any air gaps and securing loose stones with the lime mortar. Apply the mortar in a flat finish, ensuring a strong bond between the mortar and the existing wall. To achieve a neat and professional look, you can use techniques such as sponging down, tapping down, and wire brushing to smooth the surface. How much mortar you apply affects which tools you use, the time taken, the affect achieved, the drying time etc.
Assessing the condition and more importantly the style of your walls is crucial in determining the best approach for re-mortaring. Whether you have regular-shaped, nicely dressed stone faces or a mix of broken shards and scraps, the construction method will play a significant role in the time it takes to mortar the wall and the type of finish you can achieve.
When it comes to applying mortar, it’s vital to pay special attention to filling all the air gaps and securing any loose stones. Depending on the complexity of your wall’s construction, this process can be time-consuming but necessary for a lasting result.
Considering your desired finish is an important step in the process. While some may prefer a more exposed stone face or even a raised mortar effect, achieving these results can be challenging if your wall is crudely constructed or deformed.
In terms of costs, the typical range for applying mortar is around 80€ to 120€ per m². To give you an idea, if you have a 70m² wall, the estimated cost would be €8,400.
We took on average 50 minute per m² to apply the lime mortar.
Sponging down or Tapping Down?
When it comes to achieving a flat finish, there are different techniques you can use.
At around 2 to 3 hours after applying the mortar, you can use a heavy-duty wet sponge to achieve a flat and even finish on the mortar. This technique not only cleans the faces of the stones but also saves you time.
Alternatively, you can opt for tapping down, which requires a stiff bristled hand brush commonly used for sweeping the floor. By tapping the wall approximately 4 or 5 hours after application, you create a stippled effect on the surface. Tapping down helps push any soft mortar into tiny air gaps, ensuring a seamless blend with the stones. It can also be effective in smoothing out small dents and ridges in the mortar.
One of the advantages of tapping down is that it reduces the amount of excess lime and sand on the face of the stones. Tapping down can also reduce any cracks that may have appeared caused by shrinkage during the drying process. This means less work during the wire brushing stage, saving you time and effort.
Before deciding which technique to use, it’s always a good idea to check with a professional and see what method they recommend for your specific project. Maybe even a combination of both?
Regardless of the technique you choose, it’s important to remove excess lime and sand from the face of the stones, reducing the amount of work required during the wire brushing stage. This will ensure a clean and professional finish for your lime mortaring project.
Typically taping down and sponging down are included in the quote, but check with your professional.
We took around 45 seconds to 1 minute per m² to tap down the lime mortar.
(NB. We used wooden handled stiff brush)
Wire Brushing
Now, let’s dive into the proper technique for wire brushing. It’s crucial to start from the center of each stone and work outward, ensuring even coverage. By angling the brush at 45° and sliding it across the stones, rather than scrubbing, you can prevent them from becoming overly shiny. If needed, a wire brush can also be used to flatten the surface of the mortar and perfect any uneven areas.
As always work from the top down and at the end we use an air line to blow off any excess loose debris.
Check with your professional if they wire brush.
We took around 10 to 15 minute per m² to wire brush the lime mortar.
Hydrochloric Acid Wash
CAUTION: THIS TREATMENT SHOULD BE USED CAUTIOUSLY, AS ACID MAY DAMAGE THE SURFACE OF SOME CALCIUM SILICATE BRICKS AND LIME MORTAR.
To prepare the surface for lime mortaring, it’s crucial to thoroughly clean the stones or bricks. We recommend using a 1:20 Hydrochloric Acid and water mix to scrub the surface and then rinsing it with clean water. Repeat if necessary. Do not soak the wall.
However, be cautious as this treatment may damage the surface of some calcium silicate bricks and lime mortar.
Alternatively, for bricks, a 1:10 solution of the acid can be used.
We took around 2 minute per m² to apply and scrub down the acid.
If you’re uncertain, consult a professional before proceeding with the hydrochloric wash.
How Much Did We Save?
| Professional | DIY | |
| Scaffolding – 12.5m x 6.5m | €2,437.50 | €0 |
| Render Removal – 70m² x €60 per m² | €4,200 | €0 |
| Raking Out – 70m² x €60 per m² | €4,200 | €0 |
| Applying Mortar – 70m² x €120 per m² | €8,400 | €0 |
| Hessian / Polythene Wrap – 70m² x €40 | €2,800 | €0 |
| Materials – check quote | €0 | €217.80 |
| Guttering | €1,100 | €350 |
| Total | €23,137.50 | €567.80 |
Costs Per Square Meter
| Per m² | Per m² / Per month | |
| Site Clearance | €25 to €60 | |
| Scaffolding | €20 to €30 | |
| Render Removal | €25 to €60 | |
| Raking Out | €25 to €60 | |
| Raking Out (with root ingress) | €80 to €120 | |
| Applying Mortar | €80 to €120 | |
| Hessian Wrap | €25 to €40 |
As shown in the tables above, we have managed to saved over €22,500 by making smart choices such as timing our project and borrowing scaffolding. One key factor in our cost savings was the decision to take on the mortaring ourselves. By doing it DIY-style, we were able to cut down on labor costs and gain valuable hands-on experience.
We also had an incredibly dangerous chimney that needed removal, we expect a professional would have charged in excess of €10,000, to remove that.
The Future for Our House
It’s crucial to highlight the importance of proper guidance and learning from experts. We are immensely grateful to our friends at Château de Montmagner, who taught us the ins and outs of lime mortar. Their expertise and guidance were instrumental in our successful renovation.
With the right knowledge and techniques, you can avoid hefty labour expenses and complete the project yourself. This not only saves you money but also gives you a sense of accomplishment and personal connection to your home.
Not only did the DIY lime mortar route help us save money, but it also had a transformative effect on our property. When we first purchased our home, the render was falling off, and the house had been on the market for an extended period. But now, thanks to lime mortaring, our house looks bright and fresh, and we are confident it will last for many more decades to come.
Does Lime Mortaring Add Value to a House?
We are excited to share that our house’s value has skyrocketed since undergoing the lime mortaring process. We believe it will at least double it’s value, and it’s a testament to the incredible impact fresh lime mortaring can have on a property.
Can Poor Mortaring Cause Damp?
Unlike cement mortar, which can seal in existing moisture and cause dampness, lime mortar allows the walls to breathe, preventing damp issues.
Choosing cement to re-mortar a lime wall will have lasting consequences. Unlike modern brick walls lime mortared walls do not have cavities and have to breathe, the use of cement will cause far reaching and long-lasting issues. Instead of curing a problem, the cement could in fact make it much worse by allowing more damp in and sealing it there.
Understanding the difference between cement and lime mortar is vital for achieving structurally sound results in your renovation work. Frost can cause cracks in the mortar causing cracks, these can lead to insect infestations, mold and further degradation. A regularly maintained lime wall can last a lifetime.
Failure to eradicate air-gaps and seal cracks whilst mortaring can allow pockets of moisture and insects into walls. It’s vital to eliminate all voids by using ensuring the mixture isn’t too dry whilst applying and tapping back firmly.
How Long Does Lime Mortaring Take?
Let’s get started with an overview of the time it took to complete this DIY project. From removing the original render to raking out and applying the new lime mortar, it took approximately 182 hours to cover a 70m² area. Keep in mind that this doesn’t include additional tasks like runs to the recycling center, site clearing, scaffolding setup, material purchasing, gutter fixing, and finding replacement tiles and stones. These little extras can easily double or even triple the total time spent. With that in mind, on average, we spent around 5 to 7 hours per square meter.
So, if you’re considering a DIY renovation project and want to learn more about lime mortaring, you’ve come to the right place. Join us on this informative journey and discover how fresh lime mortar can be a game-changer for your DIY renovations.
Lime Mortaring: Essential Knowledge for DIY Renovators
