Strengthening of existing steelwork is often necessary where a change of use or geometric modifications are made. In the case of floor beams, it is particularly common to introduce web openings to accommodate services such as air conditioning etc. The use of carbon fibre reinforced polymer composites (CFRP) overcomes several of the difficulties associated with the use of traditional strengthening techniques with welded steel plate. CFRP has a superior strength to weight ratio than steel and has excellent corrosion resistance. In comparison to welded plate, CFRP is generally easier to handle and apply. Currently there is a scarcity of research on the application of CFRP to steel beams with web openings and the work that does exist is limited to relatively small-scale beams. In the present work a numerical model validated against experimental work by the authors is used investigate the application of CFRP to floor beams common in everyday practice. The results show that practical and efficient layouts of CFRP can be used to achieve similar or greater strengthening effect in comparison to traditional steel plate methods.