Frequently Asked Questions

Person sitting at desk on mobile phone with tape measure in hand


If you want to find out more about where we deliver, what colours our dry verge is available in or how much roof ventilation you need?  The answers to these and more can be found below.

If you can't find what you are looking for, please feel free to contact us and we'll be happy to help you.

1.    Delivery areas and timescales

Our standard delivery service to all UK Mainland addresses takes 2 to 3 working days (Monday to Friday) from the time the order has been processed. Alternative weekend, named day or next day delivery services may be available, depending on the delivery address and postcode. Please note that deliveries to the Scottish Highlands, Northern Ireland and British Islands can take an extra 2 to 3 working days. We do not deliver to the Scottish Islands or Isles of Scilly.

2.    Do you deliver direct to site?

We can deliver direct to site. Please give full address details when placing your order. We deliver Monday to Friday (excluding Bank Holidays). Please ensure someone is on site to receive the goods.  Our courier will deliver the goods as near as possible to the delivery address as far as a hard road permits. If we are unable to deliver goods an additional charge may be incurred.

3.    Do you offer next day delivery?

Next day delivery service is available on most of our products. Costs may vary depending on the day you choose. Next day delivery will be available if you order before 1pm but restrictions do apply.  For more information please contact our customer experience team.

4.    What do I do if my delivery hasn’t arrived?

We aim to deliver all items within the delivery window.  In the rare event of an item not arriving on time, please double check your order confirmation because if you have ordered multiple items, they may be delivered on different days.  If you still require assistance after checking please contact our customer experience team.  Please include your order number and full details of what hasn’t arrived so we can help you faster.

Manthorpe Building Products
Brittain Drive
Codnor Gate Business Park
Derbyshire, DE5 3ND

Reception: 01773 303000
Customer Experience Team:  01773 303030

1.    What is the length of a linear dry verge unit?

There are two crucial dimensions to consider, one is the products overall length:



The other dimension is the coverage length:

2.    What colour options are available for your dry verge?

Our dry verge products come in a selection of colour options, to suit a variety of roof coverings and roofline styles used by our customers.  When choosing dry verge, the choice is entirely yours but often a contrasting colour looks best, Slate Grey is our most popular colour.

3.    Due to the short lengths of the Linear Dry Verge does the dry verge look continuous once fitted?

The system has been cleverly designed to reduce inconvenience and installation time by decreasing the unit lengths, without damaging the aesthetic appeal of a continuous verge run.  Other than a few, discreet join grooves along the run, the verge skillfully gives the illusion of being continuous.

View our full range of Dry Verge products.

1.    Is GDRR suitable for a mono-ridge?

Our dry ridge products have been specifically desgined and vigorously tested for use on a duo pitched roof only.

2.    What length does GDRR come in?

The GDRR is available in both 6 metre and 3 metre packs to suit a longer or shorter ridge length.  An extra union is included in each pack to join multiple kits together for longer ridge runs.

3.    Can the GDRR be fitted with clay ridge tiles?

The GDRR has been specifically designed for use with the majority of concrete ridge tiles. Please see our new Ultra Ridge product, an alternative which is suitable for clay ridge tiles and when the GDRR is not suitable.

View our full range of Dry Verge Ridge products.

1.    How do I connect a flexi-pipe to my slate vent?

Our versatile GRPA Flexible Pipe can be efficiently used with any of our tile and slate ventilator range. With the Mini Castellated tile vent (GTV-MC) and Single Pantile vent (GTV-SP) the flexible pipe can be fitted to the tile vent directly. For use with all other Manthorpe tile vents you need to use the Mechanical Extraction Adaptor (GTV-AD).  For further guidance and help installing the product please click here.

2.    Can you connect an extractor pipe to your tile vents?

With our Mechanical Extraction Adaptor (GTV-AD) in place, a 4inch pipe can be easily secured to most products within our tile and slate ventilator range, with the exception of our new Universal Tile Vent CURV, Mini Castellated and Single Pantile vents which come complete with an adaptor (a round spigot).

View our full range of Tile & Slate Ventilation products.

1.    To meet the requirements from BS5250 how much roof ventilation do I need?

Understanding how much ventilation is required within a roofspace is not always straightforward.  However, here are a few useful tips and guidelines to get you started which will work in almost all common roofs;


Diagram for roof pitches of more than 15 degrees


For roof pitches of more than 15º

10,000mm²/m is needed at the eaves.  Pitches above 35° or with a span exceeding 10m, allow an additional 5,000mm²/m at the ridge.






For flat roofs and pitches of 15° or less

25,000mm²/m is required at the eaves or low level to ensure a cross flow of ventilation.







For warm roof details

25,000mm²/m is required at the eaves, with 5,000mm²/m at high level and a continuous 50mm gap between the insulation and membrane. Dormer windows, fire barriers and pitch changes etc., create separate voids within the roof space, ventilation must be maintained to these areas at high and low level.






Mono pitch roof details

5,000mm²/m ventilation gap at high level, with 10,000mm²/m or 25,000mm²/m at low level depending on the roof pitch.

(For further information on the ventilation requirements for the control of condensation in buildings, refer to BS 5250)

2.    How many Felt Lap Vents are required for my loft space and how far part should they be spaced?

Our Felt Lap Vent (G630) is a popular product for helping increase ventilation retrospectively within loft spaces that are suffering with condensation problems.

To get you started, we would recommend placing one ventilator into every other rafter bay down at low level. This should then be repeated on the opposing side. The vents will help to combat the problem of condensation build up in any roof space with a lapped felt / membrane construction.  Please be aware that the opening of felt laps on the property may adversely increase the wind uplift load on the tiles/slates and affect the driving rain resistance of the roofing felt, for more information see BS 5534:2003, 5.8.1 &

3.    What is the free airflow value of the G504 1.25m Roll Panel?

The product provides an unobstructed, continuous gap of 25mm, which equates to 25,000mm²/M.

4.    Can the G504 be trimmed to suit a shorter eaves length?

Yes, the product can be easily trimmed to suit the eaves detail using suitable cutting tools on site.

5.    Do the G504 panels need to be unclipped at the popper connectors?

No, the popper connectors are a crucial design feature, allowing Manthorpe to create the unique extended width of 1.25m.

6.    Can the G504 panels be overlapped to further increase the panel width?

Yes, if you have a detail that requires, the roll panel can be overlapped either with a second G504, or with another product within our roll panel range.

7.    How is the G504 roll panel fixed to the rafters?

The roll panel can be simply stapled or nailed to the top face of the rafters. The roofing underlay and battens should then be installed as soon as possible to prevent strong wind and sun light damage to the roll panel vent.

8.    Can the roll panel be used for a hipped roof detail?

Yes, the roll panel is also suitable for a hipped roof detail. Please see link below for step-by-step fitting instructions explaining how this can be easily achieved.

MBP1143d - G500, G502, G503 & G504 Roll Panel Vent Fitting Instructions (web).pdf (

9.    How many G504 Roll Panel vents are in a box?

The 6m G504 roll panel comes in boxes of 2

​10.    Can the G504 roll panel be used for a hipped roof detail?

Due to the versatile, castellated profile design, the roll panel can be rolled out and secured in place without the worry of uneven rafter centres.


If you need more information or advice on roof and eaves ventilation or any other aspect of a specific project, you can get in touch with us through our contact page webform or by email or phone, and we’ll be happy to help. 


1.    How many underfloor vents do I need?

At Manthorpe we understand the importance of following up-to-date building regulations and standards when making design decisions.  The number of vents required depends upon the floor area, or the perimeter of the floor.  For further guidance and confirmation on how many underfloor vents are needed within your property, please follow the links below:

2.    I'm building an extension with a solid floor.  How do I ventilate under the suspended floor of the original house?

This can be easily achieved using our Remote Void Ventilator (G962).  The G962 can either be connected directly to our G930 air brick or, to the back of both of our underfloor vents. A 4inch pipe of suitable length can then be slotted in place via the adapter exit point. Please click here for more information:

3.    How many extension sleeves do I need?

Each Extension Sleeve (G961) provides up to an extra two brick courses of height to either our Telescopic Underfloor Vent (G960) or Dual Extended Telescopic Underfloor Vent (G965).  The sleeve can also be fitted to the base of the underfloor vents providing an extra 150mm horizontal extension through wider cavities.

4.    Do you do a 9x6 or 9x9 air brick?

Yes, our Combination Air Brick (G930) 9x3 air brick can also be combined to easily create both an 9x6 and/or an 9x9  air brick.  Our air bricks are availble in a range of six colours: Terracotta, Buff, Brown, Blue/Black, White and Grey.

View our full range of Wall & Floor Ventilation products.

1.    Do you supply leaded trays?

Yes, we supply both unleaded and pre-fitted traditional lead or Performance lead replacement trays. All our cavity tray products can be supplied with either code 4 or code 5 lead flashings to suit a variety of design requirements.  Please note flashed trays are made to order, for more information please contact our customer experience team.

View our full range of Cavity Trays products.

1.    Can you paint over the GL250 ot GL250-03?

We would not advise painting over our GL250 loft door, due to the risk of seizing the mechanism.  However, painting over the GL250-03 would not be an issue.

2.    What is the U value for each door?

To make it easy for our customers, we offer a variety of loft access doors with differing Thermal Transmittance / U values.  Please see a simplified overview below of what each loft door offers in terms of U value:

  • GL250 = N/A
  • GL250-035-EPS = 0.35W/m2k
  • GL250-035-PU = 0.35W/m2k
  • GL250-015-PU = 0.15W/m2k

3.    What do the K, R and U values mean?

  • The K value / thermal conductivity value is a materials ability to conduct heat. The lower the thermal conductivity of a material, the better it is at preventing heat from easily passing through it. Therefore, the lower the K value the better. Measured in W/mK.
  • The R value / thermal resistance of a material refers to its ability to prevent heat transfer at a given material thickness. Therefore, the higher the R value the better. Measured in m2K/W.
  • The U value / thermal transmittance is a measurement of the rate of heat transfer through a material or detail. Therefore, the lower the U value of a material or detail the better. Measured in W/m2K.

4.    Do you supply fire rated access panels?

Yes, we can offer our customers a range of fire rated access panels of varying sizes.  Bespoke sizes are also available via contacting our customer experience team.

5.    Can you supply fire rated access panels with a cylinder lock?

Yes, all Manthorpe fire rated access panels are fitted as standard with a 'T' key lock.  However, all size versions are also available with a cylinder key lock.

View our full range of Loft & Access products.


From our first foray into the building industry through to our latest product innovations, Manthorpe Building Products has grown year on year thanks to a philosophy of continuous investment and development. 

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At Manthorpe we pride ourselves on our high quality standards, not just for the products that we produce; but for our design, manufacture, sales and delivery processes as well.

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Innovation has always been at the core of the company.  From new technology investment to in-house research and development, Manthorpe is constantly looking ahead to meet the needs of the industry.

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