The house should be constructed so that doors and windows fit snugly in their frames and the frames are set tightly in the walls. It is better to initially construct the house well rather than patch it up later with sealants.
Sealing gaps in the construction
Caulking compounds, such as silicone, latex or butyl based fillers, can be used to seal cracks between skirting boards and floors, where pipes or ducts penetrate walls, and at the junction between different construction materials. Care should be taken to locate the cause of the crack before sealing it. Some cracks are caused by movement of clay foundation soils which swell when wet and shrink when dry. Such recurrent movement would tend to open and close the cracks.
Only weather resistant products should be used in exposed areas. Sealants are available in cartridge form which is applied in a caulking gun, or in small tubs, applied with a putty knife.