Things to consider when choosing your sash window repairer is the check the level of repair that is being undertaken. We have viewed and come across many inadequate repair methods. This ranges from cheap 2 part polyester filler repairs, more commonly known as 2 pac which although sold as an exterior repair system is usually unsuitable for major exterior timber repair. The 2 part polyester fillers are the same compound as car body fillers, they are prone to cracking and breakdown when exposed to movement and moisture. We’ve all seen cracked blistering paint on old car wheel arches when they have been cheaply filled rather than had metal replaced. The same theory applies to timber windows, timber expands and contracts as it is exposed to temperature and moistures changes, 2 part fillers often crack and come away from the joining timber and allow moisture in behind which then accelerates the rate of deterioration. There is also evidence that the 2 part filler compound actually absorbs moisture once the paint seal is broken. 2 part fillers still have there place for minor or decorative repairs but for major timber repairs in the heavily weathered areas a much stronger system or repair is required. Another example we have come across is removing part sections of rotten timber such as the front nose of cills and glueing new pieces to the remaining timber. To explain the main issue here we need to realise that the original section of timber was jointed to the surround timber and continues into the sides of the sash box, often just removing part of the affected area means the rot is still present in the surrounding adjoining timber and will continue to deteriorate, often prematurely causing the new sections of timber to rot or brake the joining seal. For full professional repair complete sections need to be removed which often involves removing and replacing or refitting joining timber to ensure the rot has been removed.