Roof Rennovation for my 100 years old Village Home In Gujarat, India

Hello - We are planning to renovate our old stone house in India. The current roof structure is all wood with manglore clay tiles. We are looking for some advice on best options to replace the entire roof with steel structure and insulated panels/tiles. We are concerned with the integrity of the new roof structure with existing walls. How should we design the new roof structure, tie the walls together as well as tie the new roof structure into the walls.

I’ve attached pictures to illustrate the condition of the house and roof structure.

Open to all advise here on what would you do if this was your house?

Your roof looks fine to me. The holes you see won't leak. Only if you stand right under it and can see the sky.
If it were my roof I'd take the tiles off, the lats(horizontals that hold tiles) bang all nails sticking out in. Change rafters that need changing. Then we put a sheet/cloth on it. It stops wind from entering you hold this with contra-lats on the rafter beams. Then re lat the whole roof. If there is a small leak then it will run off the undersheat. Just retile and insulate the underside. Or you could do it from the top, but then you're changing a lot and might not have enough tiles.
Having said all this, I'm pretty sure Indian roofing techniques require differing standards, so best to speak to differing local roofercompanies. Make sure you come across as kind of knowledgeable about roofs or you will pay more money. That's why asking here about it is a good thing. You ll learn roof talk... Good luck!

Hugo Morvan wrote:Your roof looks fine to me. The holes you see won't leak. Only if you stand right under it and can see the sky.
If it were my roof I'd take the tiles off, the lats(horizontals that hold tiles) bang all nails sticking out in. Change rafters that need changing. Then we put a sheet/cloth on it. It stops wind from entering you hold this with contra-lats on the rafter beams. Then re lat the whole roof. If there is a small leak then it will run off the undersheat. Just retile and insulate the underside. Or you could do it from the top, but then you're changing a lot and might not have enough tiles.
Having said all this, I'm pretty sure Indian roofing techniques require differing standards, so best to speak to differing local roofercompanies. Make sure you come across as kind of knowledgeable about roofs or you will pay more money. That's why asking here about it is a good thing. You ll learn roof talk... Good luck!

One more thing I forgot to mention is we have existing termite issue. We completed the treatment for it and believe it is good now however did not want to chance them returning back. With the wooden roof structure being very old, we were thinking to just replace the entire roof structure with steel. Thoughts?  

With the wooden roof structure being very old, we were thinking to just replace the entire roof structure with steel. Thoughts?  

Termites are an issue, I have a few questions.
- Have they got into the roof?
- Is termite resistant timber available?
- is that room becoming a habitable one?
-When you say steel, do you mean steel structure and steel roofing iron?

Hardik,

The rood structure looks quite pretty but for the house it's too leaky and I do not mean thermal insulation but entry point for insects.
You have two options:

-adapt what you have by adding ceiling planks and filling the void with some insulating material (sheep wool would be nice, breathing and natural)

-change it completely to a new roof, in this case you will need to pour a concrete bond beam on entire wall perimeter; 20-25 cm thick, properly reinforced (four 12 mm rebars with stirrups every 40 cm should be sufficient); you would encase anchors in the bond beam, so the future steel structure could be securely connected

I would prefer the first option - to preserve the traditional craftsmanship, but only if the walls are intact (not cracking) and if the termites never got to the roof structure.

1. Yes, termites have found thier way into all wood structure.
2. No, not locally and would prefer to remove wood from structure
3. Yes, however not for daily use. maybe on special occasions or once a year if that.
4. Yes. Steel rafters, ridge, purlins, etc.. whatever is necessary for new roof.

John C Daley wrote:

With the wooden roof structure being very old, we were thinking to just replace the entire roof structure with steel. Thoughts?  

Termites are an issue, I have a few questions.
- Have they got into the roof?
- Is termite resistant timber available?
- is that room becoming a habitable one?
-When you say steel, do you mean steel structure and steel roofing iron?

Unfortunately due to termite issues, we will have to proceed with completely new roof design/structure.

Thank you for sharing your insights with concrete bond beam. Can you think of any other alternatives to best anchor the new steel roof?

Also, The second house is built with mud walls ONLY. How should we anchore the new steel roof structure under that situation?

Cristobal Cristo wrote:Hardik,

The rood structure looks quite pretty but for the house it's too leaky and I do not mean thermal insulation but entry point for insects.
You have two options:

-adapt what you have by adding ceiling planks and filling the void with some insulating material (sheep wool would be nice, breathing and natural)

-change it completely to a new roof, in this case you will need to pour a concrete bond beam on entire wall perimeter; 20-25 cm thick, properly reinforced (four 12 mm rebars with stirrups every 40 cm should be sufficient); you would encase anchors in the bond beam, so the future steel structure could be securely connected

I would prefer the first option - to preserve the traditional craftsmanship, but only if the walls are intact (not cracking) and if the termites never got to the roof structure.

Hardik Dhaduk wrote:Hello - We are planning to renovate our old stone house in India. The current roof structure is all wood with manglore clay tiles. We are looking for some advice on best options to replace the entire roof with steel structure and insulated panels/tiles. We are concerned with the integrity of the new roof structure with existing walls. How should we design the new roof structure, tie the walls together as well as tie the new roof structure into the walls.

I’ve attached pictures to illustrate the condition of the house and roof structure.

Open to all advise here on what would you do if this was your house?

Also, The second house is built with mud walls ONLY. How should we anchore the new steel roof structure under that situation?

Traditionally walls of old building were thick and either they did not need bond baams and if they needed it was done by using heavy timbers or in case of ashlar stone building (temples) by pouring lead into chiselled grooves to connect the large stones.
You will not use wood due to termites.
Using large ashlar stones would be more expansive than the building.

Since you are already mixing new and old by wanting to replace the wood roof with metal then I would really recommend a proper concrete bond beam. It ties all walls together and loads them in an uniform way, preventing cracking and greatly helping during seismic event. It also helps to prevent lateral forces exerted by the roof structure, especially if it's planned to be heavy: steel or heavy timber with rooftiles or slate. It can be easily plastered to blend into the building. It also solves the problem of anchoring.

If anchoring into the stone itself you can use either drill directly and use for example Hilti or Sikadur epoxy and althread rods or by using regular concrete anchors (expanding). Althread rods would be better, because with relative short anchors there would be a greater chance that the anchor would land on a mortar joint in a wall built from irregular stones.

In case of anchoring directly to mud wall, it's much more difficult, as the cob does not want to hold metal by friction. I have tried to use expanding anchor - I have drilled a hole, inserted the anchor, set it (it exapnded0and then after screwing a bolt and unscrewing it, it became loose due to weak crumbling nature of the material. Eventually I have used the following approach:
-I have bought stainless allthread rods 5/8" and cut them to 100 mm pieces (for window frame installation) and 200 mm (for doors).
-I have drilled them 25 mm deep on a lathe and threaded them inside to form M10 thread
I had to buy a small used lathe, all tooling and study a little to accomplish it, but it was still cheaper than buying Hilti anchors of the same size (galvanized, not stainless). In India you would probably purchase them cheaply or someone would fabricate them for even less money.
-Then I used Sikadur epoxy to glue them into the wall. The hold so well that I would have to break the wall to remove them.
If I had to attach anything to the top of the mud wall, I would do the same. It would be better to attach a steel top plate first (some double T beam) and THEN bolt steel rafters to the beam. It would distribute the roof weight better over the length of the wall, instead of concentrating all the loads in the points of rafter attachment in a weak cob material. It would be good to do some basic calculations to determine the minimum number of bolts for the top plate, so the strength of the mud wall would not be compromised with too much point load. The beam would also work as a bond beam (if sufficiently large). And the same could be done for the stone wall.
In case of the mud wall, the concrete bond beam would distribute the loads much better. The heavy reinforced concrete structure would absorb all the static and dynamic roof load and the walls would just have to hold the concrete weight.

How thick are the stone and mud walls in those buildings?

Cristobal, I wonder about the merits of drilling into mud walls through the top, bursting of the wall may occur.
Steel straps running down the wall vertically with a couple of bars through the wall say, 2 feet and 3 ft down from the top would be better to hold the roof down.
Of course a top plate of either termite proof timber or a concrete beam to carry any truss is a good idea.
Are you going to use the same style of roof design, posts etc in the middle and a ridge beam,
or clear span trusses across the room and battens on top?

Thank you for this insight.

Stone Wall = 18" thick minimum... maximum 24".
Mud Wall = 18" thick minimum... maximum 24".

Cristobal Cristo wrote:Traditionally walls of old building were thick and either they did not need bond baams and if they needed it was done by using heavy timbers or in case of ashlar stone building (temples) by pouring lead into chiselled grooves to connect the large stones.
You will not use wood due to termites.
Using large ashlar stones would be more expansive than the building.

Since you are already mixing new and old by wanting to replace the wood roof with metal then I would really recommend a proper concrete bond beam. It ties all walls together and loads them in an uniform way, preventing cracking and greatly helping during seismic event. It also helps to prevent lateral forces exerted by the roof structure, especially if it's planned to be heavy: steel or heavy timber with rooftiles or slate. It can be easily plastered to blend into the building. It also solves the problem of anchoring.

If anchoring into the stone itself you can use either drill directly and use for example Hilti or Sikadur epoxy and althread rods or by using regular concrete anchors (expanding). Althread rods would be better, because with relative short anchors there would be a greater chance that the anchor would land on a mortar joint in a wall built from irregular stones.

In case of anchoring directly to mud wall, it's much more difficult, as the cob does not want to hold metal by friction. I have tried to use expanding anchor - I have drilled a hole, inserted the anchor, set it (it exapnded0and then after screwing a bolt and unscrewing it, it became loose due to weak crumbling nature of the material. Eventually I have used the following approach:
-I have bought stainless allthread rods 5/8" and cut them to 100 mm pieces (for window frame installation) and 200 mm (for doors).
-I have drilled them 25 mm deep on a lathe and threaded them inside to form M10 thread
I had to buy a small used lathe, all tooling and study a little to accomplish it, but it was still cheaper than buying Hilti anchors of the same size (galvanized, not stainless). In India you would probably purchase them cheaply or someone would fabricate them for even less money.
-Then I used Sikadur epoxy to glue them into the wall. The hold so well that I would have to break the wall to remove them.
If I had to attach anything to the top of the mud wall, I would do the same. It would be better to attach a steel top plate first (some double T beam) and THEN bolt steel rafters to the beam. It would distribute the roof weight better over the length of the wall, instead of concentrating all the loads in the points of rafter attachment in a weak cob material. It would be good to do some basic calculations to determine the minimum number of bolts for the top plate, so the strength of the mud wall would not be compromised with too much point load. The beam would also work as a bond beam (if sufficiently large). And the same could be done for the stone wall.
In case of the mud wall, the concrete bond beam would distribute the loads much better. The heavy reinforced concrete structure would absorb all the static and dynamic roof load and the walls would just have to hold the concrete weight.

How thick are the stone and mud walls in those buildings?

We are still trying to better understand the options for the roof design. Given the current conditions of the house and assuming concreate bond beam is used to anchor the roof; what would be your recommendation to account for any seismic events and lateral forces exerted by the roof?

John C Daley wrote:Cristobal, I wonder about the merits of drilling into mud walls through the top, bursting of the wall may occur.
Steel straps running down the wall vertically with a couple of bars through the wall say, 2 feet and 3 ft down from the top would be better to hold the roof down.
Of course a top plate of either termite proof timber or a concrete beam to carry any truss is a good idea.
Are you going to use the same style of roof design, posts etc in the middle and a ridge beam,
or clear span trusses across the room and battens on top?

Hardik Dhaduk wrote:what would be your recommendation to account for any seismic events and lateral forces exerted by the roof?

You should talk to a structural engineer in the area where the house is located.

Western Gujarat has highest seismicity in India. On the other hand, the house is still standing and seems fine (except the termite affected roof). Seismic retrofitting can be more or less intrusive. It would not make sense to surround an old house with concrete beams, but since you are already considering the roof replacement - a good concrete bond beam will help. It holds the walls together and resists expanding forces exerted by the gable/hip roof.
Since you want to convert the building to a livable house it would make sense to build walls inside in such a way that they will be perpendicular to the long walls and spaced 3-4 m apart. They will brace the long walls, reinforcing them. Then a continuous bond beam can be poured over all exterior and interior walls (I did it for my house). It's possible that the fact that the walls are 450-600 mm, helped to survive quakes in the past. Building with thick/low walls are more resistant than thin and tall.  Because of that I would recommend to build the interior walls at least 400 mm thick - they would look compatible with the old building and would also have comparable mass to the exterior walls.

Cristobal, what material would you recommend fot those interior walls?

John C Daley wrote:Cristobal, what material would you recommend fot those interior walls?

I was thinking about it.
For the mud walls I would use compressed earth blocks/adobe. I consider this building to be more seismic resistant than the one built from irregular stone.
For the stone building - to preserve its building system to some extent it would be nice also to use stone - of the same type, but I would opt for stone ashlars - at least with split faces (usually cheaper than sawn, but it depends on the supplier and the equipment they have). If not stone, then the second bet would be solid bricks.

I have seen work done with adobe in Peru where is is earthquake prone.
Bamboo slats were installed within the mud walls to slow down the collapse of them in an earth quake.