Future-Proofing Interwar Suburbia - External Insulation Envelope on a 1930s semi

Pebbledash cement render came off this 1930s semi first. We then fixed mineral wool boards across the front, side and rear, including the bay window walls and the entrance porch, carrying the rear detail through to meet the extension roof insulation so no gap is left at the junction.

The finish is a highly breathable silicone render, with grey mosaic render over the plinth insulation and the ventilation grilles kept clear. We refitted the downpipes to the new wall line, put powder coated aluminium sills on the bay, and repainted the decorative timber.

Photograph External wall insulation to a 1930s semi detached house in Hemel Hempstead, Hertfordshire

02EWI with mineral wool, Hemel Hempstead

EWI with mineral wool, Hemel Hempstead

03Pebble dash cementitious render being taken down

Pebble dash cementitious render being taken down

04Insulation to rear elevation, detail showing the EWI joining the extension roof insulation to remove thermal gap

Insulation to rear elevation, detail showing the EWI joining the extension roof insulation to remove thermal gap

05Mineral wool boards being adhered to masonry wall

Mineral wool boards being adhered to masonry wall

06Mineral wool boards being mechanically fixed to side wall

Mineral wool boards being mechanically fixed to side wall

07Rockwool boards being mechanically fixed to front wall

Rockwool boards being mechanically fixed to front wall

08Rockwool boards mechanically fixed to bay window walls

Rockwool boards mechanically fixed to bay window walls

09Insulation boards fitted in entrance porch

Insulation boards fitted in entrance porch

10Downpipes being refitted to suit new wall level

Downpipes being refitted to suit new wall level

11Plinth insulation boards installed around bay window

Plinth insulation boards installed around bay window

12Highly breathable EWI Pro Silicone Render applied on rear wall

Highly breathable EWI Pro Silicone Render applied on rear wall

13Highly breathable EWI Pro Silicone Render applied on side wall

Highly breathable EWI Pro Silicone Render applied on side wall

14Bay window completed with powder coated aluminium windowsills

Bay window completed with powder coated aluminium windowsills

15Downpipes re-fitted to new wall level after external wall insulation installed

Downpipes re-fitted to new wall level after external wall insulation installed

16Grey mosaic render over plinth insulation with ventilation grilles

Grey mosaic render over plinth insulation with ventilation grilles

17Insulation & rendering completed on bay window walls with decorative timber re-painted

Insulation & rendering completed on bay window walls with decorative timber re-painted

18Insulation & rendering completed on porch walls

Insulation & rendering completed on porch walls