Wall insulation in Iwerne Minster

Working out what you have. Cob is usually rendered so you cannot see it, but the wall thickness gives it away, often 500mm or more, along with deep reveals and slightly uneven faces. Flint and rubble walls look similar and behave similarly. Later brick extensions and post-war houses may have a proper cavity, and that gets the borescope treatment: width, whether it is clear, and whether an old fill has slumped or the cavity is wet.

Cob, and why sealing it is fatal. Earth walls in Iwerne Minster hold and release moisture constantly. Put an impermeable lining or a cement render on one and the water that gets in through the top, the base or a failed gutter has nowhere to go. It collects at the back of the barrier, the earth loses its strength and the timbers built into the wall rot. This is not a slow inconvenience, it is how cob walls fail.

What cob is lined with. In Iwerne Minster, wood fibre board bedded in lime and finished in lime plaster, or a lime based insulating plaster where the wall is too uneven to take a board. It gives less thermal performance per millimetre than a rigid foam, so it goes on thicker, and that is the correct trade. The dew point moves into a build up that can dry rather than one that cannot.

The hat and the boots first. On any earth or rubble wall in Iwerne Minster the roof overhang and the base do more for it than insulation ever will. Gutters running, downpipes discharging clear, ground level dropped away from the wall, cement render and cement pointing removed where it is trapping water. We will not line a wall that is still getting wet, and we will say so.

Cavity fill where there is a cavity. On the later Iwerne Minster houses, bonded bead for a narrow, obstructed or exposed brick and block wall and blown mineral wool for a wide, clean, sheltered one. Drilled from outside, filled, holes pointed to match. One day, and Part L sets what the finished wall should reach.

Where a rigid board is right. On a sound modern Iwerne Minster wall or a later extension, insulated plasterboard or PIR such as Celotex or Kingspan on a batten or stud frame with taped joints and a continuous vapour control layer is the correct build up. Different walls want different answers, and the mistake is to use one specification on a whole house.

External systems. EWI with a mineral or lime render carrier can be done breathably and it keeps the whole wall warm and dry, but on a cob cottage in this village the appearance is controlled and the answer is usually no. It is worth asking about on a rear elevation or a later extension.

Junctions and air. Reveals, thresholds, the floor junction, the eaves and the joist ends built into the wall are the cold bridges and the rot risks together. Shallow reveals take an aerogel laminate. And an old cottage that has been tightened up needs trickle vents, working extract fans and air bricks kept clear, to Approved Document F.

Before anything is priced, Thomas finds out what your walls are made of. In Iwerne Minster that runs from cob, and flint and brick, in the older houses to post-war cavity walls.

Where there might be a cavity, he drills one small hole and looks with a borescope to see whether it is empty, dry and wide enough. His written quote then lists that survey, the insulation chosen and how thick it is, the making good at windows and doors, any extra ventilation, and the waste.

Cavity fill is injected from outside, working off a ladder, a tower for a bungalow or scaffold for a taller gable, and the holes are filled to match. Lining a solid wall is done one room at a time: furniture moved, the wall prepared, breathable boards fixed, then plasterboard or lime plaster, with the reveals returned neatly. Any cavity fill should come from a registered installer with a CIGA certificate, and the waste goes each day. If we find damp or rot, we photograph it and price the repair before a board goes up.

Internal lining needs no planning permission, per the Planning Portal's insulation guidance. The exception is a listed cottage, where consent reaches internal work too under section 7 of the 1990 Act; you can look up whether yours is on the list through Dorset Council's listed building pages. Insulating outside alters the face of the wall and is a planning question, and the Iwerne Minster Conservation Area covers the village. Building control comes in under regulation 23 once more than half a wall is renovated.

Ring rather than use the form if damp or mould has turned up on an outside wall since it was insulated. With cavity fill, it can mean rain is crossing the cavity on the fill itself.

On a lined solid wall, it is more often warm indoor air meeting a cold spot at a corner or reveal. We work out which it is before removing anything, because each has a different cure. Tell us what the outside of the wall is finished in, as hard cement render on an old wall is a common culprit. Scheduled work runs Monday to Friday, 8am to 6pm. A missed call gets returned as soon as we can.

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Iwerne Minster has plenty of homes built before 1919, and where a cottage turns out to be cob under lime render, it needs its own approach. A cob wall is not weak, it is moisture dependent. Dry, it will outlast most of the brick around it. Wet, it turns back into the field it came from.

That gives a clear order of work, and insulation is not first on it. Keep water off the top and away from the bottom: roof overhang, gutters, downpipes, ground level. Take off cement render or pointing that is holding water in. Only then think about warmth, and use lime and wood fibre when you do.

The honest advice is often that the walls are not where the money should go at all. Loft insulation to full depth, draughts sealed round doors, floors and unused chimneys, and secondary glazing will cut more of the heat loss you actually feel than lining a cob wall, and none of them risk the fabric. If somebody quotes you for wall insulation on a cob cottage without asking what is above your head or what the gutters are doing, be careful.

Nearby places we also cover for wall insulation, with straight-line distances from Iwerne Minster, and the other trades we offer in Iwerne Minster itself.

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