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We had the pleasure of working with these clay blocks by Wienerberger; they certainly make for an interesting and warm build. They can be used for solid wall construction with appropriate render/plaster; however, the extension we built was a 50mm cavity with handmade bricks on the outer leaf. Porotherm T7 - 425 MW The external blocks have insulation built in to avoid the need for insulation in the cavity; this also means there's nothing that can potentially breach the cavity. The blocks we used for an internal wall have air gaps that will act similarly when heated and keep the walls warm. Being made from clay, they already feel far warmer than concrete blocks, It is possible to achieve low U-values and retain heat better with a higher thermal mass. The Porotherm blocks are laid using a roller with a 1mm bed joint, This may seem difficult at first but is actually far easier once you have the first course set out perfectly; long straight runs can be run in amazingly quickly. Cuts are done using an alligator saw due to the width and softness of the blocks; a disc cutter will easily cut through the smaller blocks. Porotherm T7 - 425 MW The guys at PorothermUK (EH Smith) were extremely helpful with their site visits and initial questions; they are the exclusive distributors of these blocks in the UK. These blocks have been featured on Grand Designs and are likely to grow in popularity as a low-carbon alternative to the current industry-standard building methods. We think these blocks are great for new builds and sizeable extensions; however, we can really see them revolutionising the industry when it comes to building blocks of flats and commercial buildings due to the speed you can achieve with long, straight walls. Porotherm T7 - 425 MW

Masonry shouldn't be painted, certainly when it comes to solid-walled properties. The paint, often plastic-based, traps moisture in the walls. Damp specialists often refer to rising damp or penetrating damp when most of the time it's better being viewed as trapped moisture. Plastic paint on brickwork, partially removed. Moisture will always find a way into your walls, both internally and externally; it then takes the path of least resistance to escape. A fresh coat of paint on the external wall will likely push it out on the inside. Tanking is often the next attempt to stop it; this will then push the moisture up or out of the easiest coating to break through. Masonry that is kept damp for long periods of time will drastically decay; the bricks or stone will become soft and break apart. Painting your house could lead to massive costs in the long run; removing the paint is a specialist job, and DOFF is often the best course of action. Once the masonry has decayed past a certain extent, the paint will need removing, and it could either need rendering or limewashing to protect it. Aggressive and abrasive methods should be avoided; sandblasting will easily remove the face of the brick, leaving it more permeable so it acts like a sponge. DOFF paint removal. Many coatings are labelled as "breathable" and yet also claim to be water repellent; some of these companies will also try to back up their products with a low SD value; these are often false. Solid-walled properties need to allow moisture to move freely, so it's not possible for any water-repellent coating to be breathable in the necessary way. Traditional coating should be the only viable option; limewash and good-quality clay-based paints are the best options. A traditional limewash is the cheapest option, especially so when being made on the job. The paint used inside your home will also have similar effects, especially if lime plaster is still present. Breathing, cooking, and showering will release moisture into the air; ventilation is important, but the coatings on your plaster can fail if inappropriate. Again, it's worth remembering that paint is often mislabelled as being appropriate for use with heritage properties or labelled as conservation friendly, It's best to stick with materials that would have been used when the house was first built. Plastic paint peeling away after moisture breaking through inappropriate plaster.

The use of hot lime has widespread approval throughout the conservation industry. Non-hydraulic lime, not to be confused with natural hydraulic lime (NHL), is far more traditional while also being more breathable, flexible, and suitable for softer masonry. Hot lime mortars are made by mixing quicklime with aggregate and water. There are many methods to this, and it should only be attempted by a trained professional. Calcium hydroxide is the chemical name for quicklime; when slaked with water, a chemical reaction occurs, and it very quickly reaches temperatures above 250 degrees Celsius. Correct PPE must be used when slaking, mixing, and using lime mortars, as you could receive serious chemical burns. When working on listed buildings, it's important to match the original mortar in strength, structure, and colour. The best way to achieve a perfect match is to send a sample off for analysis. The choice of aggregate massively impacts how a mortar performs and looks; it might be that the original mortar had impurities in it, giving it a more hydraulic set. The use of pozzolans like brick dust and ash will show up when the mortar is analysed. If your property has soft bricks and is of traditional solid wall construction, you should probably be using a non-hydraulic mortar. A lot of so-called professionals will only recommend a lime mortar using NHL3.5 as the binder; this is usually completely unsuitable. Most modern-day bricklayers and builders will only recommend a cement-based mortar with hydrated lime in it. This is in no way a lime mortar; the hydrated lime purely acts as a plasticiser, making the mortar more fluffy and workable. Cement-based mortars should always be avoided when it comes to rebuilding and repointing traditional lime-built masonry. Hot-lime mortar