'Chaining' a building

[le rouge]

I have an outbuilding which is basically a wash-house and a garage with a loft area that I am looking to convert into living accomodation. The building dates from 1909 and is reasonably sound but needs a new roof. I understand that the walls need to be chained before a new roof could be put on in order to strengthen it before the new weight is added.

Anyone know what is involved in this process and how much it is likely to cost? (guesstimate obviously but based on your experience). The end walls are 5m and the long walls 9m.

 

[Anton Redman II]

Broadly Chainage is a layer of U shaped cement blocks with triangular reinforcing inside wired together at the corners. It is not the weight of the roof that is the issue it is that the weight of the apex of the roof pushes the walls out wards via the roof timber.  The outward force can be counteracted by beams running across the roof and that is the route I would go rather than chainage unless I needed to have the roof off anyway.

Link below gives you the prices for rod and blocks. Problem is you need to take the roof off and either knocks off 20 cms of height or raise the building by 20 cms.

http://www.bricodepot.fr/bordeaux/search/node/chainage

Add € 100 for concrete and two man days.

[Gluestick]

Until the geometric realities of walls and buildings were properly understood, it was common for badly designed roof structures to push side walls out: the apex opened up its angle slowly and the load was then exerted via the sides of the apex and pushed the walls slowly and inexorably outwards.

That's why, eventually, the "A" Frame, with a robust bottom cross brace was invented. Once a good A frame is in situ, the load is a simple downforce owing to the sheer weight of the roof, on each outside and internal (Where load bearing) wall.

Since additional beefy sized cross supports can be heavy, (And impact upon free floor space) often, the solution is to "Tie" the bottoms of the main roof timbers laterally, using metal rods, flattened at each end and bolted securely through the trusses. This type of construction is commonly seen in France with new halls and similar: such as Salle de Fêtes.

Many "Builders" of the Bodgit and Legget variety have undertaken loft conversions in France and in order to promote head height, simply removed the cross beams and replaced these with a smaller section much higher up the truss........

With the expected result.

[Www]

[le rouge]

Thanks for your input. The roof definitely has to come off. The A frame is OK but the remaining timbers have to be replaced. Thanks also for the link.

[BIG MAC]

I may be tempted to weigh up the pros and cons particularly if it's a rubble building as the reinforced concrete does provide a uniform formation level for wall plates and can provide some lateral restraint (Paticularly if you continue the ring beam inside the gable either in rc concrete or using RSJs)

[Araucaria]

I'm waiting for a professional friend to help me put a chain round the top of this:

[IMG]http://i585.photobucket.com/albums/ss293/Vanman15/skeleton.jpg[/IMG]

This building will eventually have solar panels for a roof, which explains the wedge of cheese shape. But here it won't be "U" shaped blocks on top of the walls: we will be clamping shuttering to both sides of the walls, putting the reinforcing in, and shovelling in the concrete after that. The concrete goes down the hollow corners too at the same time, which also have reinforcing in them. The reinforcing in the corners will be tied to the reinforcing on top of the walls.

[BIG MAC]

Araucaria that's  what I was alluding to. Also if you place Polystyrene within the formwork you will be able to create a rebate which will allow the installation of stone or brick 'slips' if you wish to preserve appearances

[Gluestick]

Thinking on this further.............

This might be useful...........

[Www]

 

[IMG]http://i461.photobucket.com/albums/qq332/PercyPee/Anchor.jpg[/IMG]