Here is a selection of Frequently Asked Questions (FAQ’s) from some of our customers, if the answer is not here then please contact us.

Sound Isolation

Q Can you supply sound proof fire rated doors for auditorium halls?

We can provide horizontal sound proof sliding doors and vertical sliding doors up to STC60 and 90 minutes fire rating. These doors are designed without floor track for easy movement of equipment in and out of the auditorium.

Q. The client requests a door opening comparison regarding which door type will transmit the most/least sound and why?

We need more information about what is to be compared. For example if your client requires STC70 this can be achieved with combination doors. A single leaf door will achieve up to STC60, the same door in a double leaf will be @ 3dB lower. Generally the higher the acoustic attenuation of the door, the less sound will be transmitted; STC 50 door: very loud sounds such as musical instruments or a stereo can be faintly heard by 99% of population: STC 60 gives Superior soundproofing with most sounds inaudible. However it depends upon the noise frequencies you wish to attenuate. If you send us your 1/3 Octave band requirements we can match our acoustic test reports and recommend the best door.

Q What is a suitable STC rating for a cinema?

Many factors will influence the choice of STC rating: sound travels through walls, floors, ceilings and structural supports so it will depend
on where the building is located and what the application is. For example: is the cinema adjacent to a busy highway? Do you require the
acoustic door to be ADA compliant? Our STC50 door is ADA compliant. The highest STC rating is STC60, however these doors are very heavy and are not suitable for busy pedestrian areas. To determine the correct STC ratings for your building we recommend consulting an acoustician.

Q I have a small hotel and we have problems as our guests rooms are very noisy from the talking in the reception and restaurant.  Most of the noise seems to be coming through the door which is very thin.  Can you supply acoustic doors to stop the noise going into the rooms? 

We can supply acoustic doors, however sound travels through walls, floors, ceilings and structural supports so changing the doors alone may not give you the outcome you desire. We recommend consulting an acoustician, they can measure the sound leakage and advise the attenuation of door you will require to isolate the unwanted noise.

Fire Rating

Q. Are your fire door products certified in the USA?

Yes, our doors are tested to UL10c and NFPA252 

Q. I'm an architect working on a Performing Arts Center. We have a stage house loading corridor and we a looking for fire rated doors that can allow a 12' clear opening with a 45 min rating. Might you have some solutions?

The door would be custom manufactured to your requirements, our doors are fire rated up to 90 minutes.

Q What is the difference between a Fire rated door and a Fire Exit Door?

A fire rated swing door is always a part of a door set and comes complete with frame, suitable hardware (a door closer is essential to ensure the door always remains closed) and a fire label.

A fire rated sliding door must be power operated and linked to the building fire alarm system, the door will close on signal from the fire alarm.
A Fire rated doors is usually an internal door contained in a fire rated wall or a fire rated enclosure such as a stairwell. The purpose of the fire door is to create or protect an escape route through a building in a fire. Fire rating of the doors will be determined by the fire rating of the wall they are contained in. Generally they will remain closed. If they are held open (for example in a corridor) they must automatically close on signal from the building fire alarm system.

A Fire exit doors is usually an external door. Generally a fire exit door does not require a fire rating (unless under certain circumstances). The purpose of the fire exit door is to allow a quick and unhindered escape into a place of safety while stopping un-authorised access from the outside. Fire exits swing doors should be fitted with a panic or push bar if it is a security door that is usually kept locked but used by members of the public in an emergency situation. The door should open easily and wherever possible, in the direction of traffic flow. 

Door size

Q We are looking for a sliding door that is 8'-0" tall by 10'-0" wide. Would it be possible to make this size?

We have manufactured custom doors up to 65’ wide x 65’ tall, contact us for larger sizes.

Q. I am looking for an exterior telescopic horizontal sliding door, what is the maximum size you manufacture?

We are a solutions company always looking for new challenges.  We would want to understand as much as possible about the application to advise you the most economic solution to meet your design performance objectives.  In theory we can manufacture a door up to 65 feet wide.

Q. What is the maximum width of a Pivot Door 8’ high?

We can manufacture Pivot doors to approximately 10' wide when the height is 8'

Door Finishes

Q. What is Polyester Powder Coated Paint? What colours are available?

Powder coat is an electrostatic paint spray process, Polyester Powder Coat (PPC) is applied as a dry powder, unlike conventional paints, the powder, PPC does not require a solvent. The coating is applied to the doors then cured at high temperature to create a hard finish that is tougher than conventional paint. Suitable for use interior or exterior applications (please advise if marine coating required). We can color match to a RAL color of your choice.

Q. What is Plastisol Coating? What colours are available?

Plastisol Coating is a PVC based coating applied in thicknesses up to 200microns during manufacture of the steel sheeting, giving a very durable finish which is suitable for interior and exterior applications and does not fade or scratch easily. Guaranteed for 10 years. Plastisol
Color Chart will be included in your quotation, contact us for more information.

Q. Can a steel door have wood veneer or cladding on the outside?

Yes, we would prepare the door to receive a veneer or cladding, we would require details of the weight and thickness of the veneer and the preferred method of fixing prior to manufacture.


Q. Can you send me your price list?

Our doors are custom manufactured, we do not carry inventory of “standard size doors”. Please send us your door schedule and any related drawings and we will provide pricing. Otherwise contact us with the door specification and our estimating team will price.

Q Can you provide pricing for oversized horizontal sliding sound control door located in Boston, MA?

We would be pleased to provide pricing, we require STC rating and door sizes as price will vary according to attenuation and size of the door.

Technical Information

Q. I have limited headroom due to existing pipework in the way. I would prefer a sliding door if possible as I don't want to lose the floor space with a large swing door. Please can you advise the smallest headroom I can fit an acoustic door in?

A. If you send us the building layout drawing indicating clear opening height and width of door; indicate the amount of side, and potential headroom available we can advise you.  The size of the track will depend on the weight of the door – so the properties of sound insulation value in STC and Fire rating will need to be understood.  With the above information we can advise you an optimum solution to fit in your space.

Q. I am currently working on the development stages of a large scale project, is it possible to schedule a time for a representative of CDL to present your products to our office?

Yes, just let us know where you are located and one of our team will arrange a presentation for you.

Q I’m looking for large double swing doors that are close to airtight.  These would be for a nuclear application that requires exterior doors that can maintain a very low leakage rate as the space will be under negative pressure. Can you help?

Yes, we provide both sliding and swing doors for Nuclear facilities, contact us with the door sizes and your specification so we can provide a quote.

Q. Would it be possible using Clark Door products to have a rated assembly with a 3'or 4' man door?

We can provide acoustic doors or fire rated acoustic doors with a man door or a set of double doors, depending upon the overall size of your door.