Thread: Router vs circular saw vs Concrete Chaser - log cabin build

Originally Posted by rustynail

Sorry, you did ask for sizes.. The splines are cut to approx 100mm. This width allows them to reach through the sap wood of the logs and into the true wood. This is important as, with time, the sap wood will degrade and compromise the seal. If your logs have more than 25mm of sap wood, increase your spline width to allow 25mm penetration into true wood.

What is the thickness of the flat gal sheet metal? Is it blade thickness?

Olly

Olly, The thickness of spline is not that important as I like to bed them into a bead of caulking sealer. The groove in the next log is filled with sealer also, the log is then rolled so the filled groove is down and lowered on to the waiting spline and so on up the wall.
The thicker the spline the better, as it cuts down on caulking compound and also helps to keep the spline straight ready for the next log.
I worry about the idea of allowing the top beam to descend with the shrinkage of the drop logs. This renders the structure to be no different to a normal log construction with notched ends, in that everything goes down as the logs shrink except the windows and door heads and sills. If you design so that all openings are framed by post and beam with the afore mentioned internal and external fascia attached to the top beam your roof will remain stable as to will the gable ends. Roof movement should be avoided where ever possible as shrinkage doesnt happen evenly round the building. Of course the logs below the windows will still want to head south, but this will be considerably less as it would only be half the number of logs, or less, than whats in a full height wall.
Shrinkage is going to be your major consideration as your logs are going to still be carrying a lot of moisture. Drying of sawn hardwood requires a year per inch thickness. And thats for sawn boards. A log can and probably will take years to dry. This is not a problem provided its factored in.

Originally Posted by rustynail

Olly, The thickness of spline is not that important as I like to bed them into a bead of caulking sealer. The groove in the next log is filled with sealer also, the log is then rolled so the filled groove is down and lowered on to the waiting spline and so on up the wall.
The thicker the spline the better, as it cuts down on caulking compound and also helps to keep the spline straight ready for the next log.
I worry about the idea of allowing the top beam to descend with the shrinkage of the drop logs. This renders the structure to be no different to a normal log construction with notched ends, in that everything goes down as the logs shrink except the windows and door heads and sills. If you design so that all openings are framed by post and beam with the afore mentioned internal and external fascia attached to the top beam your roof will remain stable as to will the gable ends. Roof movement should be avoided where ever possible as shrinkage doesnt happen evenly round the building. Of course the logs below the windows will still want to head south, but this will be considerably less as it would only be half the number of logs, or less, than whats in a full height wall.
Shrinkage is going to be your major consideration as your logs are going to still be carrying a lot of moisture. Drying of sawn hardwood requires a year per inch thickness. And thats for sawn boards. A log can and probably will take years to dry. This is not a problem provided its factored in.

Rustynails, Many thanks once again. I will follow your advice.

As you mentioned "

Originally Posted by rustynail

Personally, I prefer to allow the logs to move down the posts as they decrease in diameter, as this means a lot less maintenance"

I chose to allow my logs to move down the posts. I am also planning to use ply glued into the post. The thickness I am looking at using is 20mm ply and set into logs and posts by 35mm. Is that sufficient as they will be structurally holding the panel logs into place. What method, material and sizes to you use for this?

(In addition I had included cyclone rods from bearer to beam holding the panels into place and to enable me to tighten horizontal logs, but engineer said I was going overboard and removed them).

Can you recommend the caulking sealer you use? I do not have confidence in local hardware knowledge. It's always been a 50/50 result on recommended products only to find out over time its good or c**p and I can't afford it with this build.

Thanks again for sharing so much.

owe you one or two

Olly, The caulking compound we use is boat caulk or deck caulk. There is a commercial log home compound available but I haven't used it. What you use is probably not all that critical for spline bedding.
For log to post joint we run two or more parallel saw cuts down the post wide enough to take a mortising adze, so about 50 to 75mm depending on the available adze. I dont recommend adzes to the untrained, so if you are not familiar, a good solid firmer chisel will do the same job. Just use the chisel bevel down and put plenty of longitudinal saw cuts into the post. Now here is the interesting bit; some years ago, when working on huts in the national parks with my father and uncle, Dad pointed out to me how rectangular grooves in end posts where inclined to split away. Where as square grooves retained their integrity. Therefore, when grooving the posts with a 50mm wide groove we go 50mm deep and for a 75mm groove we go 75mm deep. I guess the stresses placed on the drying timber tend to want to peel the sides of the groove out, so the deeper the groove the greater the stress on the groove sides. The drop logs are then shaped at the ends with a chainsaw the same as you would do rails in a post and rail fence. This is a quick and easy process, with only the grooves in the post being a bit laborious. I dont think your ply splines will be as quick to do.

Originally Posted by rustynail

I dont think your ply splines will be as quick to do.

Somehow, I tend to agree with you, or do I mean "somewhat"

Thanks

I will discuss with building certifier about making changes to my horizontal log attachments and material.