Heat rises, and in a poorly insulated house a large share of it leaves through the top-floor ceilings. Laying insulation across the loft floor is one of the simplest ways to keep that warmth downstairs. Many older homes still have a thin, flattened layer put down decades ago, and some have none at all.
We install and top up loft insulation as part of our roofing work. Because we are roofers, we look at the whole roof space, not just the depth of the quilt. Insulation that blocks the eaves, buries electrical cables or leaves the water tank exposed to frost can cause more trouble than it solves, so we deal with those details as part of the job.
How much insulation does a loft need?
For a loft insulated at ceiling level, around 270mm of mineral wool is the depth commonly recommended today. Building regulations set the target as a U-value, and when existing insulation is being renewed or substantially added to, they expect a standard that in practice means roughly that sort of depth, depending on the product.
It is usually laid in two layers. The first fills the gaps between the ceiling joists, and the second is rolled out across the joists at right angles, covering the timber and closing the cold bridges they create. Topping up an existing layer is often possible if it is dry and in reasonable condition.
Coverage matters as much as depth. Small uncovered strips at the edges, around the hatch or behind the water tank let a surprising amount of heat escape, so we take as much care over the awkward corners as the open middle of the loft.
Materials and where each suits
- Glass or rock mineral wool rolls: the standard choice for open lofts, non-combustible and easy to lay between and over joists.
- Blown loose-fill: useful for lofts with very low headroom or awkward corners where rolls are hard to place.
- Sheep's wool and wood fibre: natural options that handle moisture well, popular in older properties, though usually thicker for the same performance.
- Rigid insulation boards: used between and under rafters when the roof slope itself needs insulating, for example in a room in the roof.
We explain the trade-offs of each for your loft, including how it will affect any storage plans you have.
Details that prevent problems later
Adding insulation makes the loft colder, which is the point, but it changes how the roof space behaves. To keep it healthy, we:
- Stop insulation short of the eaves, or fit rafter trays, so outside air can still flow in.
- Lift cables on top of the insulation where we can, and fit covers over recessed downlights designed for that purpose.
- Leave the area directly below the cold water tank uninsulated, so rising warmth helps protect it, and insulate the tank and pipework instead.
- Insulate and draught-seal the loft hatch, a common source of warm, moist air entering the loft.
- Keep a safe clearance around flues and chimney breasts as the manufacturer requires.
Older Tyneside homes and their lofts
Many Victorian and Edwardian houses across Newcastle have slate roofs laid straight onto battens, often with no felt at all. Those lofts tend to be well ventilated through the gaps between slates, which helps once insulation is added, but they can also let in wind-blown rain and snow, so we check the roof covering before laying anything new.
In a Tyneside flat, the loft usually sits above the upstairs flat and is often included in its lease. If you are the downstairs owner, insulating your own ceiling is a different job, so check your lease first. Topping up loft insulation on its own is not usually notifiable to building control, but we will tell you if your job is part of wider work where it is.
