London Guarantee

Exterior Construction Details for Single Family Homes

In order to assist our Builders, London Guarantee has prepared this series of exterior details that address the most common problem areas on a single family home.

In the case of multi-family projects, or non-typical single family homes, the services of a building Envelope Professional should be retained.

London Guarantee’s goal is to provide unparalleled technical services to our Builders.

These details are provided to our builders as a guide only. It is the Builder’s responsibility to ensure their adequacy/completeness. The use of these details by anyone other than London Guarantee’s Registered Builders is strictly prohibited.

Window Sill Detail

Illustration Points:

1) The critical junction is the corner of the opening. The use of a prefabricated corner piece may help. The waterproofing membrane should not extend up the sides of the opening more then 6”.
2) Building paper lapping (4” minimum, shingled laps)
If peel & stick is used as the waterproofing membrane it should have minimal contact with the wood.
3) Ensure that all framing members are protected from the weather, and that the moisture content is below 19% prior to insulating and installing the vapor barrier.

This detail creates the ability for the window opening to deal with incidental water which may enter due to a window leak.

Window Head Flashing Detail

Illustration Points:

1) Flashings should extend beyond the flange of the window. One way of achieving this is to run the flashing the full width of the trim board. In areas where no trim board is present, the flashing should extend beyond the window flange by a minimum 1”.
2) End-dams at the end of the flashing can be created by bending up the ends of the flashing, or applying a small bead of caulking.
3) The main body of the building paper should always overlap the flange of the flashing

Window Head Flashing Detail

Illustration Points:

1) Building Paper Lapping (4” minimum, shingled laps)
2) Flashing Slope (20 degrees minimum).
3) Gap Between Cladding & Flashing (1/4” minimum) above and below.
4) Do not use Vinyl drip flashings, because they are manufactured without a positive slope. Use only adequately sized and sloped (20 degrees minimum) metal drip flashings.
5) All types of building paper and house wraps should always be installed in a shingled fashion, the upper sheet should always overlap the lower sheet a minimum of 4”.
6) Never relay on any self adhering membranes (red tape, peel and stick) in lieu of properly shingled laps.
7) In areas where wood frame building settlement/shrinkage is exepected (box joists, headers, etc.), the minimum gap between the flashing and the cladding should be incresed to 1/2”.

The above noted detail can also apply to other flashing details such as barge boards, exterior vents, etc.

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