When planning a garden room, one of the most critical decisions is choosing the right wall construction. Two of the most common options are CLS stud walls and SIP (Structural Insulated Panel) walls. But which one is better for insulation, cost, and DIY installation? Let’s break it down.

1. Understanding Wall Construction

A garden room's performance depends on more than just insulation thickness—it’s about the full wall structure. Here’s how each method is built:

CLS Stud Wall Construction

• External Cladding: Timber or metal cladding

• Sheathing: 11mm OSB

• Framing: 89mm CLS timber studs at 400mm centers

• Insulation: 75mm PIR insulation between studs

• Sheathing (Internal): 11mm OSB

• Batten Framing: 25mm batten for plasterboard fixing

• Internal Finish: 12mm plasterboard

SIP Panel Construction

• External Cladding: Timber or metal cladding

• Sheathing: 11mm OSB

• Insulation: 75mm PIR or 75mm EPS (depending on the panel type)

• Sheathing (Internal): 11mm OSB

• Batten Framing: 25mm batten for plasterboard fixing

• Internal Finish: 12mm plasterboard

By including all components, this ensures a fair comparison of wall performance.

2. Thermal Performance: Which Keeps You Warmer for Less?

The U-value measures how much heat a wall loses—the lower, the better. Here’s how each wall type performs:

What Does This Mean?

• PIR insulation performs significantly better than EPS. If you choose SIP panels, opting for PIR over EPS will save you money on heating and cooling.

• Both CLS stud walls and SIPs with PIR offer similar insulation performance. The difference lies in cost and installation method.

Want to see real-world heating costs? Try our U-Value & Heating Cost Calculator to compare different wall constructions instantly!

3. Cost Breakdown: CLS vs. SIP Panels

Which One Is More Affordable?

We compared the cost of both options for a 4m x 3m garden room, including materials and labor:

✅ Building with SIP panels was £2500 + VAT more expensive than using CLS stud walls.

While SIPs allow for a quicker build, their higher material cost makes CLS frames the more budget-friendly option.

4. DIY or Professional Build: Which Is Easier?

If you’re a DIY enthusiast, your choice matters. Here’s why:

• CLS stud walls can be built by a single person with basic carpentry skills. The process is straightforward—cut timber, assemble the frame, insulate, and finish.

• SIP panels require at least two people and specialized tools for cutting and fitting. The panels are heavy, and any mistakes can be costly to fix.

If you plan to self-build your garden room, CLS is the more manageable choice.

5. The Verdict: Which One Should You Choose?

Choose CLS stud walls if:

✔️ You’re looking for a more affordable option

✔️ You want to DIY your garden room

✔️ You like flexibility in design

Choose SIP panels if:

✔️ You prefer a faster build time

✔️ You’re happy to pay more for prefabrication

✔️ You have help with installation

Both options offer great insulation performance—but if cost and DIY-friendliness are priorities, CLS stud walls are the better choice.

Final Thought: Don’t Overpay for Inferior Insulation

Many budget garden room companies use EPS insulation in SIP panels to cut costs, but as we’ve seen, this significantly increases heating and cooling costs. If you’re paying for a premium garden room, make sure you’re getting PIR insulation!