How Much Loft Insulation Do I Need? (Clear, Local, No Nonsense)

If you live anywhere in Stockport, Heaton Moor, Cheadle, Burnage, Didsbury, Reddish or nearby, the correct depth for loft insulation is simple:

100mm between the joists + 200mm across the top = 300mm total

This matches modern UK standards (around 270mm), but gives better real-world performance — especially in older homes.

The problem?

Most Stockport homes have 50–120mm in total.

That’s why bedrooms feel cold, the heating is on longer, and energy bills climb every winter.

This guide explains exactly what depth you need, why it matters, and how to upgrade it safely.

The Correct Loft Insulation Depth (Explained Without the Jargon)

The UK recommended depth for mineral wool insulation (which is what 95 percent of homes use) is 270mm.

Here’s the layout:

1. 100mm Base Layer

Installed between the joists.
This stops heat from escaping directly through the ceiling below.

2. 200mm Top-Up Layer

Laid across the joists.
This gives full coverage, eliminates cold patches, and creates the “blanket effect” that actually keeps heat inside the home.

Total:

100mm + 200mm = 300mm
(We go slightly above recommended to account for settling over time.)

We always install KNAUF insulation — the industry standard.

Why 300mm Is Needed in Stockport Homes

Most houses in the Heatons, Cheadle, Burnage and Reddish were built long before insulation standards existed.

The problems we see weekly:

• Old yellow insulation (around 80–100mm)

• Thin patches from DIY boarding

• Damp corners

• Missing insulation near eaves

• Cold spots where heat escapes quickly

Even newer builds often don’t meet the full depth if storage boarding was added incorrectly.

Upgrading to a full 300mm system can:

• Reduce heat loss by up to 25 percent

• Shorten heating runtimes

• Improve bedroom temperatures

• Reduce condensation risk

• Make loft boarding safe and effective

How to Check Your Loft Insulation Depth

If you want to check yourself, here’s how:

1. Lift a section of existing insulation

2. Measure the thickness

3. Look for:

   • Cold spots

   • Thin edges

   • Wet sections

   • Crushed areas under old boards

4. Check if there’s a full second layer on top of the joists

5. Look in corners and around the hatch

But for a proper reading, we recommend the £29 Loft Health Survey — which measures depth in multiple areas and checks moisture, airflow and boarding suitability.

Learn more:
https://hiclimited.co.uk/loft-insulation-boarding-stockport

Signs You Don’t Have Enough Loft Insulation

Stockport homeowners most often report:

• Cold bedrooms in the morning

• Heating staying on longer

• Condensation in the loft

• Musty smells or damp insulation

• Drafty loft hatch

• High energy bills

• Mould on rafters

• Old yellow insulation visible

If you see two or more, your insulation depth is almost always insufficient.

What It Costs to Reach the Correct Depth

Here’s what Stockport homes typically pay:

100mm KNAUF base layer

From £15 per m²

200mm KNAUF top-up

From £15 per m²

Full 300mm system

Most homes land between £20–£30 per m²

If old insulation needs removing:

Add £10 per m² for safe bagging & disposal.

Optional:

• LAP vents (to prevent condensation): £8–£12 each

• Loft hatch insulation: £100–£150

• Raised loft boarding: £20–£30 per m²

Final quote provided after the Loft Health Survey.
Survey fee is waived if you book the work.

Why the Correct Depth Isn’t Enough on Its Own

Even perfect insulation fails if:

• There’s no ventilation

• The loft hatch leaks warm air

• DIY boarding compresses the insulation

• Damp has already formed in the corners

This is why the Loft Health Survey checks the entire system, not just depth.

Raised loft boarding options →
https://hiclimited.co.uk/loft-insulation-boarding-stockport

Can You Over-Insulate a Loft?

No — not with mineral wool.

What causes problems is:

• Blocking airflow

• Compression

• Damp

• Incorrect boarding

So more depth is never the issue.
Airflow is.

And that’s why we fit LAP vents when needed.

If you’re unsure whether your insulation meets the correct depth, book the £29 Loft Health Survey.

You’ll get:

• Depth measurements

• Damp/condensation analysis

• Ventilation checks

• Photo evidence

• Clear recommendations

• No-pressure quote

Survey fee is waived if you book the work.

Call 07441 356128 or message to book.

Home Improvement Contractors Ltd
Also trading as: Heatons Handyman

Address : Heaton Moor, SK4 4NS

📍Serving Manchester | Reddish | Heaton Moor | Heaton Chapel | Edgley | Stockport | Denton | Hyde | Didsbury | Heaton Norris | Cheadle | Cheadle Hulme | Bramhall

Phone: 07441 356128

Monday–Saturday: 8:30 AM – 4:00 PM
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