When considering having a loft conversion to your home, the first thing to establish is if the existing height within your roof is tall enough. The general rule of thumb measurement is 2.2m from the top of the existing joists to the underside of the ridge (the point in the middle).
If your roof is lower than 2.2m it generally means a legal loft conversion is not possible as the finished height within the loft would be under 2m. However, as an alternative, to create the necessary height required to achieve a liveable loft space, your existing ceilings to your upstairs rooms can be removed and the new structural floor can be constructed at a lower level than the original ceiling. This operation, although slightly eats into the original height of your upstairs rooms, creates the height required for a loft room. The downside to this process is that you will have to vacate your home while this element of the work is carried out. The duration of this operation is normally 2 weeks and comes at the very beginning of the build.
The majority of all loft conversions will have a flat roof constructed to them. The covering which makes them water tight can be achieved using various products, with 2 standing out as the industries norm. The first being a 3 layer felt systems and second GRP (glass reinforced plastic).
Three Layer Felt System
Three Layer Felt Systems have come a long way from the early days. They are no longer laid with hot bitumen and have stone chippings put on top. They had a stereotypical belief they were only good enough for your shed or garage. The products used today are a 3 layer membrane system, applied with the use of a gas gun. These felts come with a 20 to 30 year manufactures’ guarantee and have the ability to heal themselves with sunlight. Even if they are constantly submerged in water, this will not affect their performance. This application is favoured on a loft conversion as the product is fully bonded to the building and has a sound deadening property, which is essential with rainfall.
GRP roofing has been on the market for a number of years, but seems to have become fashionable in recently, not only due to the product price falling below the cost of the 3 layer system, but more importantly the ease of application. It has become so easy to install it could be classed as a DIY product. This product, if fitted correctly, will also carry a 20 to 30 year guarantee. The product is essentially a fibre class skin laid over a thin fibre membrane, with purpose made corners and drips that are stuck together. Although this can be used on a loft conversion, the biggest downside is the noise it generates when it rains. As 99% of lofts conversions are bedrooms, we would not advise the use of GRP. Furthermore, as this product is not fixed but laid on the roof decking, it is also prone to lifting in high winds.
Based on past experience the three layer felt system out performs the GRP on multiple levels.
It require’s a trained BRP professional for installation
It’s less noisy and more secure in heavy rain / wind
This is a common question asked when placing an order for a loft conversion. We can only share our many years of experience on the use of both these products. Whilst wooden French doors may look more in keeping with your house, they have fundamental flaws which do not lend themselves to being a good choice for a loft conversion.
Traditionally, wooden exterior doors are designed to open outwards (excluding front doors). The reason they open out is due to the weathering between the door and frame. Rain water cannot ingress past the frame and into the building as the door will seal against the frame on the inside and send any water outwards. When you reverse this process, once rain water gets round the door, then there is nothing within the frame on the inside to re direct the water and so a leak will occur. French doors have to open inwardly on a loft conversion due to the local authority regulations. Wooden doors and windows also need a lot of maintenance as the effects from the elements greatly increase with a loft conversion. Our experience has seen lots of these doors falling within a matter of 12 months due to either rotting or shrinkage and it is also worth noting that this product came become draughty. For these reasons loft companies generally exclude these from whatever guarantee they issue.
UPVC comes maintenance free, leak free and draught free. This is achieved simply by the nature and design of the doors. They will have specially designed drainage points and pull in handle systems to seal out any draughts. Now that UPVC comes in many colours and wood effect graining, it is hard to tell that they are even made from UPVC looking up at them from the ground floor.