Connecting extension to external wall insulation

Question

Hi, I currently have external wall insulation around my whole house and I want to add a kitchen extension, how do I connect the extension to the house, especially the wall plate for the lean to roof. All advice is greatly appreciated.

Richard · Answer

Cut through the insulation in line to where the new extension is going so you can fix your extension walls back to the original solid house whether it’s timber frame or masonry

Simon · Answer

Connecting an extension to a house with external wall insulation (EWI) involves careful planning to ensure structural integrity, weatherproofing, and thermal performance. Here's how you can approach this:

1. Determine the Existing EWI System Details
Thickness: Identify the thickness and type of insulation (e.g., EPS, PIR, or mineral wool).

Fixing Method: Understand how the insulation is attached (e.g., mechanical fixings, adhesive) and if there is a render layer.

2. Create a Structural Connection for the Wall Plate
Strip Back Insulation: Remove a section of the EWI where the extension wall will join. This exposes the original brick or blockwork to provide a secure base.
Anchor the Wall Plate: Fix the wall plate for the lean-to roof directly to the exposed brick/blockwork. Use appropriate heavy-duty fixings such as resin anchors or frame fixings.
Thermal Bridging: Minimize thermal bridging at the connection point by using insulation-compatible fixings or by adding thermal breaks.

3. Sealing and Reinsulating
Seal the Joint: After the extension is connected, seal all gaps between the EWI and the new structure to maintain airtightness.
Reapply Insulation: Extend the external insulation over the exposed areas around the joint to ensure continuity. Match the insulation type and thickness to avoid cold spots.
Blend Renders: Apply a compatible render over the reinstalled insulation to match the original finish.

4. Roof Integration
Ensure the lean-to roof integrates with the house wall above the EWI line. Flashing should extend over the insulation layer to prevent water ingress.

5. Building Regulations
Consult with a structural engineer or builder to ensure compliance with local building regulations, particularly regarding load-bearing walls, thermal performance, and fire safety.

6. Professional Assistance
For complex connections like this, it’s recommended to work with a builder or specialist familiar with EWI systems to ensure the best results.
Proper planning and execution will help maintain the benefits of your EWI while creating a robust connection for the extension.

Steve · Answer

Hi, you will just cut a void in the insulation to make it continuous or cut the insulation back and join to the existing brickwork.

Mark · Answer

After the foundations have been concreted and brickwork up to damp level, then an item called a 'firfix' which is a stainless steel flat plate with connectors which is screwed to the building. Then slide the connectors in at every 3 course of brickwork/every course of blockwork. join as many as required to get to the top of your walls. Fix on both inner and outer leaves of structure.Wall ties bridging both leaves at every block course.
Years ago builders would 'tooth' out the old and stitch in the new, but as foundations moved fractionally the tended to crack along the join.

The roof, if it is a lean-to style, would have a timber fixed to your house with bolts secured with a chemical fix resin. Then joist hangers would be nailed along at required lengths to accept the roof rafters which in turn are secured on the wall plate(4''x 2'') with truss clips nailed with twist nails. plate straps hold the plate down the wall at 2 meter maximum gaps .
If a gable style then the first rafter can be fixed but usually roof trusses are self supporting. If a hand cut roof is used then a concrete pad-stone is inserted into the wall and the ridge beam sits on this.
I hope this gives you a better understanding.

Robert · Answer

Hi it rob clarks property services the answer from the last tradesmen is correct the installation will have to be cut back so you can fix the wall plate tight on to the brickwork. Hope this can answer your question

Paul · Answer

You will have to get hight of wall plate pluss go 200 mm above for lead. Work and cut the insulation to suit

Aaron · Answer

The builder that does the work will tell you what's best.  If you are doing it yourself ask a builder to come and have a look as after market product are different.  And give them a drink for the advice

Ross · Answer

Connecting a kitchen extension to a house with external wall insulation requires careful planning to ensure a seamless integration. Here's a general guide on how to connect the extension to the house, specifically focusing on the wall plate for the lean-to roof:

1. **Assessment and Planning:**
   - Evaluate the existing external wall insulation and determine the best way to connect the extension without compromising the insulation's effectiveness.
   - Plan the extension layout, ensuring it aligns with the existing structure and accounts for any potential challenges posed by the insulation.

2. **Wall Plate Connection:**
   - Install a ledger board to the existing house wall to support the roof of the extension. This ledger board will act as the connection point for the wall plate of the lean-to roof.
   - Ensure the ledger board is securely attached to the house wall, taking into account the external wall insulation. Proper flashing and sealing should be applied to prevent water intrusion.

3. **Wall Plate Installation:**
   - Attach the wall plate of the lean-to roof to the ledger board using appropriate fasteners. Make sure the connection is structurally sound and weatherproof.
   - Consider using spacer blocks if needed to accommodate the thickness of the external wall insulation and maintain a secure connection.

4. **Roof Integration:**
   - Once the wall plate is securely in place, proceed with constructing the roof of the extension, ensuring it integrates smoothly with the existing house structure.
   - Properly insulate and seal the junction between the extension roof and the house wall to maintain energy efficiency and prevent water penetration.

By following these steps and potentially seeking guidance from a qualified contractor or structural engineer, you can effectively connect your kitchen extension to a house with external wall insulation while ensuring structural integrity and weather resistance.

Connecting extension to external wall insulation

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