How to Elevate a House
– Principle of raising a house: increasing the living space from above
– Regulations for raising a house
– Raising a house: the hydraulic method
– Raising a house by covering the roof
– Reinforcing the attic floor
– Installing a timber frame when raising a house
– The importance of insulation in house building
The space requirements of a family change as they grow: rather than selling and buying back a property, many owners choose to extend their home, either by using the attic space where possible or by selecting a side extension or elevating the house.
The principle of the extension: increasing the living space from above
Sometimes, the development of the attic is impossible:
– when the land use coefficient is reached;
– when the attic is too low.
In these cases, raising the height is the ideal solution, even if it is rather complicated: the weight brought in must be calculated to support the whole load-bearing walls. In the case of conventional buildings, the walls are often strong enough, which is rarely the case for a steel or timber frame house.
The old framework is then removed, and a new one is installed on the previously raised walls. The insulation is then reinforced and brought up to current standards.
Regulations for raising a house
A building permit is required if the house is larger than 150 m². Below 150 m², it is necessary to make:
– a declaration of works to the town hall;
– a tax declaration (you are creating useful space, which is subject to specific taxes).
It should be noted that some communes limit the height of buildings: ask your local council for information.
Concerning thermal standards, the work will be subject to the requirements of the thermal renovation regulations of the building code.
Raising a house: the hydraulic method.
Only a specialised company can install this efficient system, but it is highly dependent on technical studies. A professional will also offer you the necessary insurance for this project.
Hydraulically raising the roof consists of placing jacks under a steel belt that has been previously put in place at the periphery of the top. The jacks are placed:
– sufficient number calculated according to the load to be carried;
– at the precise locations determined by:
◦ the weight to be lifted;
◦ the shape of the roof;
◦ the type of roof structure.
Once the roof is at the desired height, the roof is shored up, and the walls are raised:
– in conventional masonry;
– in reinforced concrete; or
– in timber frame.
Raising a house by covering the roof.
When the house is inhabited during the work, the roof must be kept:
– only the first few rows of tiles are removed;
– The floor is then reinforced, and the walls are raised to accommodate the new roof structure;
– once the new roof is installed, the old one is removed.
Remember, only professionals can do this for you.
Reinforcing the attic floor
When the trusses are removed, the floor is also removed and must be recreated. To do this, the workers install load-bearing beams parallel to the trusses to create a new joist. Various criteria are studied for this installation:
– the distance between beams;
– the span of the beams;
– reinforcement of the hopper;
– connections and masonry, etc.
Installing a timber frame when raising a building
Today, wood is making a comeback. In the case of a building extension, it is now possible to “lay” a timber frame house on top of your own home. The advantage of this method lies first of all in its possibilities: where masonry walls and a conventional framework would be too heavy, a timber frame can be suitable.
However, this type of elevation looks like a cube added to the original house, with a very modern appearance, which may put off some owners, as well as seduce them…
The work consists of:
– removing the existing roof;
– creating a slab-floor;
– attaching glued laminated beams to it;
– creating the belt of the platform thus designed;
– filling the spaces between the beams with insulation and fixing a floor (chipboard, etc.);
– Assemble the timber frame walls;
– attaching the rafters to create the roof, with rain screen and batten lining;
– applying zinc sheets to the flat roof;
– insulating the room.
The importance of insulation in house building
When extending a house, it is essential to insulate the roof and the newly created walls.
Therefore, it is important to ensure that the original walls are correctly joined to the extension: a waterproofing test can be useful to check the continuity of the insulation.
– External insulation can be chosen in the case of an extension: this method is very effective and will avoid losing a few square metres.