High Water Table Solutions

Conservation-Friendly Approach

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What Is a High Water Table?

High water table occurs when the level of groundwater rises to or near the surface, saturating the upper soil layers. The water table represents the upper surface of the soil, where the pores and fractures of the ground are filled with groundwater. This occurs due to excessive water accumulation beneath the ground, often from heavy rainfall or water seeping down from higher elevations into the surrounding soil.

High Water Table Impact on Old Buildings

Old buildings, especially those constructed before the 1870s, often lack a damp proof course (DPC). A DPC prevents dampness from rising up the walls. When there’s no DPC, the bottom of the wall is directly connected to the water table, which acts as an unlimited water supply.

Here’s how high water table affects old buildings:

Rising damp: the height of the water table plays a crucial role in the development and intensity of rising damp. Without a DPC, moisture from the water table can rise through the walls. Evaporation creates a pressure difference, drawing up more moisture and salts from the ground. This ongoing water intake leads to rising damp within the walls.
Masonry damage: high water tables mobilize soluble salts within the masonry which are carried up by rising damp into the wall fabric. These salts harm the building fabric, leading to deterioration. Additionally, a damp masonry can be subject to more frost damage, affecting the long-term integrity of walls, plastering and other structures.
Timber decay and corrosion: excessive moisture promotes timber decay and corrodes metal components within the building. Wooden beams, joists, and other structural elements become vulnerable to rot when constantly exposed to damp conditions.
Structural problems: the constant presence of moisture weakens building materials, affecting their integrity over time. Foundations, walls, and floors may suffer structural damage due to the saturated soil. Settlement issues, uneven settling, and compromised stability can occur on buildings situated on a high water table.
Reduced thermal efficiency: dampness in the wall fabric reduces the thermal efficiency of the building. Cold, damp walls are less effective at retaining heat, leading to radiating cold, discomfort for the occupants, unhealthy environment and potentially higher energy costs.
Health risks: mould growth due to damp conditions can pose health risks to occupants, especially those with respiratory issues.

In summary, a high water table can create significant challenges for old and listed buildings, impacting their condition, stability, longevity and habitability.

high-wt-core-conservation — High water table in an area

Solving High Water Table Problems in a Sympathetic Way

All the above problems can be addressed in a conservation-friendly sympathetic way, using building-friendly technologies and breathable, traditional materials. For starters, good drainage is essential to channel away as much liquid moisture as possible from the property.

Additionally, a combination of the following solutions have proven to be very effective in handling high water table related problems:

Magnetic DPC system: to reduce the amount of moisture present in the wall fabric, the magnetic DPC system is a good non-invasive choice. Instead of blocking the ascent of water by physical or chemical means, a magnetic DPC takes a completely different approach: it increases the breathability of the wall fabric, allowing moisture to evaporate from the wall fabric much easier - resulting in drier, warmer walls.
Lime replastering with special lime plasters: wall sections damaged by the excess moisture and salinity should be replastered with special lime plasters resistant to moisture and salts, such as the Rinzaffo MGN Roman base coat followed by a lime-cocciopesto second coat. For walls requiring some rebuilding, reinforcement or structural consolidation the Betoncino Consolidante MGN lime plaster is an excellent heritage-friendly choice.
Thermal plasters for improved thermal comfort: the thermal efficiency of damp walls in a high water table areas can be quite low as damp, evaporating walls are often radiating cold. To improve the thermal efficiency of old buildings in a building-friendly way, we have high-performance lime thermal insulation plasters, with or without aerogel. Low U-values of 0.5 or lower can be achieved with only a few centimetres of breathable lime thermal insulation. More information on the lime thermal insulation page.

Unlike modern cement-based tanking products, traditional lime plasters are also healthy materials that are naturally anti-bacterial. Some lime plasters such as Cocciopesto (a traditional Roman mix of lime and brick dust) or lime-hemp or lime-clay plasters are excellent humidity regulators creating a healthy, low-humidity environment.

Recommended Products

Here are the typical recommended materials / products for this solution. Other product variations are possible as we have different types of plasters and paints, depending on your needs or application. Please get in touch to discuss additional options.

Rinzaffo

Roman Salt-Resistant Waterproof Lime Plaster

Base

Waterproofing

cocciopesto-deumificante-banner5-core-conservation

Cocciopesto Deumidificante

Humidity Regulating Cocciopesto Lime Plaster for Cellars

Non-invasive Rising Damp Remedy

Damp Proof Course

Work Specifications

Here are the recommended work specifications for this solution.

Base, Waterproofing

Application Guide

Rinzaffo Controspinta MGN

[15-20 mm] ABOVE GROUND: Lime base coat, applied as:

█ [5-10 mm] Levelling / Repair: level, repair and point uneven walls first. The material consumption here can vary, depending on substrate condition. Very uneven walls (e.g. after cement plaster removal) can take up more material.
█ [10 mm] Protective base coat: apply a 10 mm coat.

[25-30 mm] UNDER GROUND: Lime waterproofing coat or for very damp wall sections, applied as:

█ [5-10 mm] Levelling / Repair: level, repair and point uneven walls first. The material consumption here can vary, depending on substrate condition. Very uneven walls (e.g. after cement plaster removal) can take up more material.
█ [10 mm] Waterproofing coat 1: apply a first 10 mm coat.

▒ [Mesh] Fibreglass mesh (10 x 10 mm): embed a mesh into the plaster for added flexibility.

█ [10 mm] Waterproofing coat 2: apply a second 10 mm coat to complete the waterproofing.

Second coat

Cocciopesto Deumidificante MGN

[15-20 mm] Lime second coat, with 15 mm for internal, and 20 mm for external walls. Applied usually in 2 coats as:

█ [8-10 mm] Second coat, first half, for vapour control.
█ [8-10 mm] Second coat, second half, for vapour control.

Finishing

Calcina Fine MGN

[4 mm] Lime finish applied as:

█ [2 mm] First half of the finish.
▒ [Mesh] Fibreglass fine mesh (4 x 4 mm): embed a mesh into the finish for added flexibility.
█ [2 mm] Second half of the finish.

Lime paint

Tinta Chiara Smooth Lime Paint

░ [Paint] Apply 1 coat of Lime Base Paint (Primer).
░ [Paint] Apply 2 or 3 coats of smooth or textured breathable lime paint.

Plaster Application

Here are some key application points about the application of each plaster, as well as links to the full application guides. Please have your plasterer read / watch the application instructions below before applying the products. If any questions, please contact us, happy to help.

Base, Waterproofing

Application Guide

Rinzaffo

VERY IMPORTANT POINTS

Here are a few very important points, highlighted in red, that MUST be respected for the correct application of this plaster.

Coat thickness: the thickness of the base coat MUST be adapted to the (damp) condition of the wall fabric. Moderately damp walls need less, very damp walls need more thickness. The correct coat thickness can be achieved the easiest the following way:
- Repair, point and level (dub out) the walls first with the Rinzaffo MGN to have a more or less level wall surface. This might take 5-10 or more mm material, depending on the condition of the fabric. Let it dry, then:
- Apply a min 10 mm (in 1 coat) for above ground level walls. Apply min 20 mm thickness (in 2 coats) for underground or extremely damp or salty walls. embedding a 10 x 10 mm fibreglass mesh between the coats – a standard practice in the industry.

Close all pores, no matter how small. Treat and apply this plaster as a tanking-grade material, NOT as a parge coat. Cover the whole wall surface thoroughly leaving no holes or gaps behind, no matter how small. Smoothen the surface, then give it a light key with a damp brush. Do not cut into the material.

Watch for dark patches after drying: damp underlying wall sections evaporate out a lot of moisture, which result in dark areas or patches as a result of surface condensation. Reinforce dark areas with extra material by applying an extra coat over these darker areas only. You can carry on with the next coat right away.

– – – – –

Clean the masonry: the plaster must be applied on a cleaned and uniformly wet substrate. All crumbling and loose parts must be removed by brushing so the masonry is free of dust, salts and oils. If possible, also wash the walls with a pressure washer; this will clean and wet the walls in one go. Close larger holes with lime mortar and pieces of bricks.

Must be the first coat: the Rinzaffo MGN plaster must be the first coat on any wall. It should not be applied on top of other parge coats or plasters because when those fail the performance of the Roman base coat will also likely to be affected.

Cement backgrounds: the Rinzaffo MGN base coat can be applied and will bond well to cementicios backgrounds. The removal of cement plasters is recommended for the vast majority of cases to restore the breathability of the wall fabric. However, in some (rare) cases, when the removal of cement would be too invasive, too costly or would not beneficial the underlying masonry, if the cement backing is stable, the Rinzaffo MGN can be applied over it for waterproofing purposes (e.g. to waterproof cement floor bases).

Salt-inhibitors or PVA bonding agents are NOT needed and should not be used before the application of this plaster. This natural lime plaster bonds very well on its own.

Masonry paints should be removed (which occasionally can be challenging) so the plaster can firmly adhere to the underlying stones or bricks. Remove at least 50% of the existing paint – the more is removed, the better.

Mixing: mix the material with clean tap water only without adding anything else (no other material or additive), until a homogenous, creamy-consistency mix is obtained.
IMPORTANT: Dry to wet mixing: plasters with hydraulic ingredients should always be mixed from dry to wet (workable) state. Add your powder to a bit of water, start mixing and gradually add more water till the right consistency is reached. This is the right way. Mixing the other way – wet to dry mixing – by starting with lots of water then gradually adding powder to the right consistency, is incorrect. Reason: excessive wetting weakens the plaster, alters its hydraulic set resulting in less performant, more friable and shorter lasting plasters.

Wet the wall fabric abundantly before applying the plaster, as well as in-between each subsequent coat. Lime plasters need moisture as they set slowly in a damp environment. If the walls are already damp, there is no need to wait to become drier, you can proceed with the application of this plaster.

Level uneven surface first: very uneven walls (e.g. stone walls or crumbling old brick walls) are recommended to be patched up and levelled first before the application of a continuous coat, to ensure the consistency and required thickness of the base coat.

Application: apply the plaster in 10 mm coats.

Light key: give the plaster a light key using a wet brush. Do not cut into the material with the edge of a trowel.

Additional coats can be applied in further 10 mm increments. Use an embedded fibreglass mesh for extra reinforcement over the recommended thickness.

Drying time: the plaster dries quite quickly, typically in 1-2 days, depending on ambient conditions. Once it has hardened, the next coat can be applied.

Application conditions: ambient and wall temperatures must be between +5 to +30°C during application. Surfaces should be protected from rain and humidity until they have completely dried (approx. 3 – 10 days depending on weather conditions).

Second coat

Cocciopesto Deumidificante

Clean the masonry: the plaster must be applied on a cleaned and uniformly wet substrate. All crumbling and loose parts must be removed by brushing so the masonry is free of dust, salts and oils. If possible, also wash the walls with a pressure washer; this will clean and wet the walls in one go. Close larger holes with lime mortar and pieces of bricks.

Mixing: mix the material with clean tap water only without adding anything else (no other material or additive), until a homogenous, creamy-consistency mix is obtained.
IMPORTANT: Dry to wet mixing: plasters with hydraulic ingredients should always be mixed from dry to wet (workable) state. Add your powder to a bit of water, start mixing and gradually add more water till the right consistency is reached. This is the right way. Mixing the other way – wet to dry mixing – by starting with lots of water then gradually adding powder to the right consistency, is incorrect. Reason: excessive wetting weakens the plaster, alters its hydraulic set resulting in less performant, more friable and shorter lasting plasters.

Application: apply the plaster in 10 mm coats.

Additional coats can be applied in further 10 mm increments. Use an embedded fibreglass mesh for extra reinforcement over the recommended thickness.

Drying time: the plaster dries quite quickly, typically in 1-2 days, depending on ambient conditions. Once it has hardened, the next coat can be applied.

Finish options: main lime coats can be optionally left without finishing. To have a finished surface any MGN finish can be applied: Calcina Fine MGN (white lime finish), Intonachino Arenino MGN (coloured lime finish) or Marmorino MGN (Venetian Marmorino finish).

Application conditions: ambient and wall temperatures must be between +5 to +30°C during application. Surfaces should be protected from rain and humidity until they have completely dried (approx. 3 – 10 days depending on weather conditions).

Finishing

Calcina Fine

Mixing: mix the material with clean tap water only without adding anything else (no other material or additive), until a homogenous, creamy-consistency mix is obtained.
IMPORTANT: Dry to wet mixing: plasters with hydraulic ingredients should always be mixed from dry to wet (workable) state. Add your powder to a bit of water, start mixing and gradually add more water till the right consistency is reached. This is the right way. Mixing the other way – wet to dry mixing – by starting with lots of water then gradually adding powder to the right consistency, is incorrect. Reason: excessive wetting weakens the plaster, alters its hydraulic set resulting in less performant, more friable and shorter lasting plasters.

Recommended thickness of the finish: 3-4 mm. For best results, the finish should be applied in two “half-coats” of 2 mm each, with a fine 3-4 mm fibreglass mesh embedded in-between. The mesh makes the finish more flexible, minimizing the appearance of fine cracks.

Various textured finishes can be achieved, depending on the finishing technique used:
- Coarse finish: by finishing the surface with a sponge or wooden trowel.
- Smooth finish: by using a stainless steel trowel, compressing and smoothing the semi-dry surface, the sand granules are pushed into the material, resulting in a smooth finish.
- Washed finish: by finishing the surface with a sponge trowel. After the surface has hardened, the surface is washed with water and blotted with a sponge to bring out the aggregate, its specific texture and colour.

Painting: as this is a breathable lime plaster, wall surfaces should be painted with a breathable mineral paint. Wallpapers and modern emulsion petrol-based paints, with no or limited breathability, should be avoided.

Application conditions: ambient and wall temperatures must be between +5 to +30°C during application. Surfaces should be protected from rain and humidity until they have completely dried (approx. 3 – 10 days depending on weather conditions).

Base, Waterproofing

Application Guide

Rinzaffo

VERY IMPORTANT POINTS

Here are a few very important points, highlighted in red, that MUST be respected for the correct application of this plaster.

Coat thickness: the thickness of the base coat MUST be adapted to the (damp) condition of the wall fabric. Moderately damp walls need less, very damp walls need more thickness. The correct coat thickness can be achieved the easiest the following way:
- Repair, point and level (dub out) the walls first with the Rinzaffo MGN to have a more or less level wall surface. This might take 5-10 or more mm material, depending on the condition of the fabric. Let it dry, then:
- Apply a min 10 mm (in 1 coat) for above ground level walls. Apply min 20 mm thickness (in 2 coats) for underground or extremely damp or salty walls. embedding a 10 x 10 mm fibreglass mesh between the coats – a standard practice in the industry.

Close all pores, no matter how small. Treat and apply this plaster as a tanking-grade material, NOT as a parge coat. Cover the whole wall surface thoroughly leaving no holes or gaps behind, no matter how small. Smoothen the surface, then give it a light key with a damp brush. Do not cut into the material.

Watch for dark patches after drying: damp underlying wall sections evaporate out a lot of moisture, which result in dark areas or patches as a result of surface condensation. Reinforce dark areas with extra material by applying an extra coat over these darker areas only. You can carry on with the next coat right away.

– – – – –

Clean the masonry: the plaster must be applied on a cleaned and uniformly wet substrate. All crumbling and loose parts must be removed by brushing so the masonry is free of dust, salts and oils. If possible, also wash the walls with a pressure washer; this will clean and wet the walls in one go. Close larger holes with lime mortar and pieces of bricks.

Must be the first coat: the Rinzaffo MGN plaster must be the first coat on any wall. It should not be applied on top of other parge coats or plasters because when those fail the performance of the Roman base coat will also likely to be affected.

Cement backgrounds: the Rinzaffo MGN base coat can be applied and will bond well to cementicios backgrounds. The removal of cement plasters is recommended for the vast majority of cases to restore the breathability of the wall fabric. However, in some (rare) cases, when the removal of cement would be too invasive, too costly or would not beneficial the underlying masonry, if the cement backing is stable, the Rinzaffo MGN can be applied over it for waterproofing purposes (e.g. to waterproof cement floor bases).

Salt-inhibitors or PVA bonding agents are NOT needed and should not be used before the application of this plaster. This natural lime plaster bonds very well on its own.

Masonry paints should be removed (which occasionally can be challenging) so the plaster can firmly adhere to the underlying stones or bricks. Remove at least 50% of the existing paint – the more is removed, the better.

Mixing: mix the material with clean tap water only without adding anything else (no other material or additive), until a homogenous, creamy-consistency mix is obtained.
IMPORTANT: Dry to wet mixing: plasters with hydraulic ingredients should always be mixed from dry to wet (workable) state. Add your powder to a bit of water, start mixing and gradually add more water till the right consistency is reached. This is the right way. Mixing the other way – wet to dry mixing – by starting with lots of water then gradually adding powder to the right consistency, is incorrect. Reason: excessive wetting weakens the plaster, alters its hydraulic set resulting in less performant, more friable and shorter lasting plasters.

Wet the wall fabric abundantly before applying the plaster, as well as in-between each subsequent coat. Lime plasters need moisture as they set slowly in a damp environment. If the walls are already damp, there is no need to wait to become drier, you can proceed with the application of this plaster.

Level uneven surface first: very uneven walls (e.g. stone walls or crumbling old brick walls) are recommended to be patched up and levelled first before the application of a continuous coat, to ensure the consistency and required thickness of the base coat.

Application: apply the plaster in 10 mm coats.

Light key: give the plaster a light key using a wet brush. Do not cut into the material with the edge of a trowel.

Additional coats can be applied in further 10 mm increments. Use an embedded fibreglass mesh for extra reinforcement over the recommended thickness.

Drying time: the plaster dries quite quickly, typically in 1-2 days, depending on ambient conditions. Once it has hardened, the next coat can be applied.

Application conditions: ambient and wall temperatures must be between +5 to +30°C during application. Surfaces should be protected from rain and humidity until they have completely dried (approx. 3 – 10 days depending on weather conditions).

Second coat

Cocciopesto Deumidificante

Clean the masonry: the plaster must be applied on a cleaned and uniformly wet substrate. All crumbling and loose parts must be removed by brushing so the masonry is free of dust, salts and oils. If possible, also wash the walls with a pressure washer; this will clean and wet the walls in one go. Close larger holes with lime mortar and pieces of bricks.

Mixing: mix the material with clean tap water only without adding anything else (no other material or additive), until a homogenous, creamy-consistency mix is obtained.
IMPORTANT: Dry to wet mixing: plasters with hydraulic ingredients should always be mixed from dry to wet (workable) state. Add your powder to a bit of water, start mixing and gradually add more water till the right consistency is reached. This is the right way. Mixing the other way – wet to dry mixing – by starting with lots of water then gradually adding powder to the right consistency, is incorrect. Reason: excessive wetting weakens the plaster, alters its hydraulic set resulting in less performant, more friable and shorter lasting plasters.

Application: apply the plaster in 10 mm coats.

Additional coats can be applied in further 10 mm increments. Use an embedded fibreglass mesh for extra reinforcement over the recommended thickness.

Drying time: the plaster dries quite quickly, typically in 1-2 days, depending on ambient conditions. Once it has hardened, the next coat can be applied.

Finish options: main lime coats can be optionally left without finishing. To have a finished surface any MGN finish can be applied: Calcina Fine MGN (white lime finish), Intonachino Arenino MGN (coloured lime finish) or Marmorino MGN (Venetian Marmorino finish).

Application conditions: ambient and wall temperatures must be between +5 to +30°C during application. Surfaces should be protected from rain and humidity until they have completely dried (approx. 3 – 10 days depending on weather conditions).

Finishing

Calcina Fine

Mixing: mix the material with clean tap water only without adding anything else (no other material or additive), until a homogenous, creamy-consistency mix is obtained.
IMPORTANT: Dry to wet mixing: plasters with hydraulic ingredients should always be mixed from dry to wet (workable) state. Add your powder to a bit of water, start mixing and gradually add more water till the right consistency is reached. This is the right way. Mixing the other way – wet to dry mixing – by starting with lots of water then gradually adding powder to the right consistency, is incorrect. Reason: excessive wetting weakens the plaster, alters its hydraulic set resulting in less performant, more friable and shorter lasting plasters.

Recommended thickness of the finish: 3-4 mm. For best results, the finish should be applied in two “half-coats” of 2 mm each, with a fine 3-4 mm fibreglass mesh embedded in-between. The mesh makes the finish more flexible, minimizing the appearance of fine cracks.

Various textured finishes can be achieved, depending on the finishing technique used:
- Coarse finish: by finishing the surface with a sponge or wooden trowel.
- Smooth finish: by using a stainless steel trowel, compressing and smoothing the semi-dry surface, the sand granules are pushed into the material, resulting in a smooth finish.
- Washed finish: by finishing the surface with a sponge trowel. After the surface has hardened, the surface is washed with water and blotted with a sponge to bring out the aggregate, its specific texture and colour.

Painting: as this is a breathable lime plaster, wall surfaces should be painted with a breathable mineral paint. Wallpapers and modern emulsion petrol-based paints, with no or limited breathability, should be avoided.

Application conditions: ambient and wall temperatures must be between +5 to +30°C during application. Surfaces should be protected from rain and humidity until they have completely dried (approx. 3 – 10 days depending on weather conditions).

Completed Projects

Here are some of our projects using this solution:

Solving Damp Problems due to High Water Table

Old Farm House Ongoing Dampness Problems

Residential

Photo Galleries

Here are some photos demonstrating this solution. Click on any image to open the photo gallery.

Flood Proofing a Flooded Extension

This old cottage has been extended a few years ago, receiving a new extension. During flooding the waterproofing of the newbuilt extension did not hold, resulting in the flooding of the building. Using the Roman lime materials the waterproofing has been reinforced, preventing future flooding.