OS Holding is a Dublin building contractor specialising in attic conversions, home renovations and house extensions. Based in Greenogue Business Park, we work across Dublin city and county, from Lucan and Clondalkin to Swords, Tallaght and Dún Laoghaire. Our attic conversion service covers dormer, Velux and full-storey conversions, with structural work, stairs, insulation and fire regulations handled in-house. We also deliver kitchen renovations, bathroom renovations, garage and basement conversions, spray foam insulation and full house refurbishments to a builders finish or turnkey standard. Over a decade of experience, fully insured, with fixed-price quotes and one project manager from survey to handover. Book a free site survey today.