Frequently Asked Questions

Call or email us for a quote or simply order online. We only need the finished weathered external kerb size, the type of Rooflight and the glass specification required to process an order.

The Rooflight will be delivered on a flatbed vehicle and it will need to be unloaded by you or your builder on site.

Please ask at quote stage how heavy the unit is likely to be. It should be unwrapped and inspected as soon as it is delivered, as any defects or damage should be reported to us within 24 hours of delivery.

All you really need is an idea of what you are looking for. Our knowledgeable staff can walk you through the order process, step by step. Ideally though, if you have the external kerb dimensions to hand this will speed up the process.

The answer to this question is not simple. A fixed Flatglass Rooflight will simply let light in while keeping the elements out. A hinged Flatglass Rooflight will also let in light but in addition, when opened it will let in air or allow for access through the Rooflight. You will need to assess your needs then discuss the various options that are available with our team of experts.

We have various types of opening Flatglass Rooflights, both electric or manual:

An electric for ventilation will open via a chain link actuator connected to a wall switch. There are various options that can be applied to the switch such as a remote control, wind sensor, temperature sensor and rain sensor.

We can also offer a manual version that is operated by a winding pole, so no need for an electrician.

An access hatch that is used for occasional access to the roof can either be electric or manual. The lids of these Rooflights open to approx. 80°. There are also manual and electric sliding versions of the access hatch.

The units for ventilation are comparable in price, so the choice seems to be between having electrics installed or not and what you are happy with in terms of controlling the Rooflight.

The electric access hatch is a bit more expensive, so please feel free to call us to discuss all the options prior to ordering.

Flatglass Rooflights are designed to be installed on a kerb up-stand. Two rows of Butyl weather sealing tape are delivered with the Rooflight and these are placed on top of the kerb. The Rooflight is bedded onto the weather seals and fixing screws are then driven into the kerb through the fixing flange that hangs down and flashes the kerb. The fixings are also delivered with the Rooflight.

Our Flatglass Rooflights are designed to be installed onto a kerb up-stand. This kerb should be a minimum of 150mm high to negate water ingress and should be level in one plane. The top of the kerb should be an angled plane to provide a pitch in order to help shed water from the glass and the kerb needs to be weathered.

The kerbs can be made of any suitable material but in our experience, timber is the most commonly used. A typical make up would be 47mm x 47mm sawn softwood carcassing of sole plate, head plate and studs, with 50mm insulation between the studs. The carcass should be sheathed to the outside with 18mm marine ply. This gives 65mm overall structural thickness. We would suggest you allow 10mm for the roof finish weathering, giving 75mm overall. The roof finish should be lapped up the outer face of the kerb and onto the top of the kerb. Add plasterboard to the inside of the kerb and decorate as required. Finish any exposed kerb top as necessary with window board, white PVC trim or paint. There is a standard drawing showing a typical kerb available here.

Generally, we recommend that the kerbs be at least 75mm thick. This is in order to properly support the rooflight frame and to adequately hide the frame from view from below. The aesthetic principle is that when you look up, all you see is glass. Thicker kerbs are fine, but the thinner the kerb the more frame you are likely see from below. Always get the suitability of the kerb accessed by a building professional before installing the rooflight; it must be robust enough to easily take the weight of the rooflight as well as any other loads imposed by wind or snow, for example.

The short answer is no, the tolerance is built into the rooflight not the kerb. For example, if you provide us with the finished weathered kerb dimensions, let’s say 1000mm down the slope by 2000mm long, we will fabricate a rooflight that’s 1046mm x 2046mm. This means that the rooflight lower flashing will slide easily over the kerb and bed the frame correctly onto the kerb top, like a box lid.

We provide two types of Flatglass rooflight; stock Flatglass rooflight sizes and a fully bespoke Flatglass service. The bespoke sizes can be any size to the nearest millimetre.

Glass is considered a rigid material but like all rigid materials it will still deflect under load. However, the more rigid the material the less it will deflect. Glass rigidity and therefore deflection is dependent upon glass pane size. The bigger the unit the less rigid it is, and the more deflection will occur, starting at the centre of the pane. When installed in the horizontal plane this means that the glass will start to dip or dish in the centre. This deflection is due to the self-weight of the material called the dead load and also to live loads like wind pressure or snow loads. Obviously, if a liquid like water were to be placed upon the glass, it will fill the dish and create a pooling or ponding effect.

To negate this, Roofglaze recommend that Flatglass rooflights are installed onto a kerb with at least a 5° fall, to help shed any water that may pool on the deflecting glass. In some instances, we may recommend more of a pitch depending upon rooflight size but ultimately the final extent of pitch is determined by the Client. That said, if a Flatglass unit were to be installed at 0° pitch this would not be to the detriment to the weathering or integrity of the IGU unit, other than water pooling on the top glass surface.

If water pooling is to be eliminated completely, the thickness of the outer skin of glass must be increased to such a point that deflection is reduced to almost zero. However, to make the rooflights safer, we heat soak toughen the glass to make it stronger, but unfortunately, this can have a detrimental effect on the glass itself by introducing a bow in the glass. This bow can cause the exact issue the thicker stronger glass was designed to eliminate. Unless it is truly excessive, the toughing bow is totally within manufacturing and industry standard tolerances and the kerb pitch will have to be increased to allow for this. One last thing to consider, water will even cling to a vertical pane of glass, via capillary action, so water can never be totally removed by simply pitching the kerb a bit.

The short answer is no. If time is short and you need the Rooflight in a hurry, just agree a finished weathered kerb size with us and we will start manufacture based upon this agreed size. The only potential drawback with this is that you may encounter difficulties during construction and be forced to change the agreed kerb sizes. If we haven’t started manufacture and this happens then it’s not a problem, but if we have started fabrication there may be additional costs involved for us to alter the Rooflight size at this stage. If time allows, it is always better to build and weather the kerb, then measure it and give us the exact dimensions.

Lead times for stock units can be as short as next day delivery. Lead times for bespoke units range from 2-3 weeks to 3-6 weeks, depending upon Rooflight type, glass spec and quantity required. To be 100% sure, please feel free to give us a call to discuss your project requirements