services > frequently asked questions

Damp Proofing

Q1 - What is the difference between Aquagard DPC and Homegard DPC?

A1 - Although both products are manufactured from pitch polymer, Aquagard is 1.25mm thick and Homegard 0.9mm thick. This determines their different uses and applications, which are fully described on the relevant data sheets.


Q2 - Can I manufacture an Aquagard cloak on site?

A2 - Marley, supported by the Code of Practice, recommends that you do not manufacture Aquagard cloaks on site, due to the complex nature of the folding and bending required. However, Marley offer a full design and manufacturing service, which actually helps to reduce valuable construction time.

 
Q3 - What is the minimum lap requirement between a DPC and a DPM?

A3 - In accordance with the Code of Practice, there should be a 50mm minimum sealed overlap between the DPC and the DPM.

 
Q4 - I am never sure where to finish the cavity fill in relation to the ground level DPC?

A4 - Cavities should be filled to 150mm minimum and preferably 225mm, below the ground level DPC.

 
Q5 - What is the method for laying a ground level DPC?

A5 - Lay the DPC on a full fresh bed mortar, DPCs should always extend to the full width of the leaf. An additional bed of mortar is than laid on to the DPC followed by the appropriate brick coursing. It is inevitable that the bed thickness at DPC level will be greater than the standard 10mm joint.



Roofing

Q1 - What is the minimum finished fall for a flat roof?

A1 - The minimum finished fall is 1:80. However, to ensure that this fall is achieved, allowance should be made for construction inaccuracies. Generally, falls of twice the minimum finished fall should therefore be assumed for design purposes.

 
Q2 - What is a cold roof?

A2 - This is also known as cold deck. The thermal insulation is placed beneath the structural deck, and above the ceiling. To reduce the risk of condensation, cross ventilation should be provided above the insulation.

 
Q3 - What is a warm roof?

A3 - This is also known as warm deck as the thermal insulation is placed above the structural deck. This form of construction is the option most frequently used in the refurbishment and new build flat roofing markets as it eliminates need for ventilation. Additionally insulation may also be used to increase the thermal properties and/or supplied as a tapered scheme to enhance inadequate falls on an existing flat roof.

 
Q4 - What are Marley Taping Strips and where should they be used?

A4 - Marley Taping Strips are 16m x 0.1m wide strips of BS 747 Type 5U felt. They are used to cover the joints on plywood decks to prevent bitumen seeping through into the building. Additionally as they are only bonded to one side of the joint, they also allow for movement between the plywood panels.

 
Q5 - Do I have to worry about maintenance of my new roof?

A5 - Maintenance of a roof is extremely important, as it ensures the life expectancy of the roof is maximised. The roof should be inspected at least once a year and preferably twice. Once in March and secondly in November. Typical items for inspection include, clearing gutters and outlets of debris, checking the condition of upstands and flashings; checking for loose laps, edge trims and faulty penetrations and loss of surface protection.