Building a deck, dimensions ?

[Västerhaninge 17]

I have 30 cm between the patio door and the ground, so there will be a layer of joists.
What dimension should the joists be, and what should the center-to-center distance be? I will use 28*120 decking boards.
Where to place the piers/how many?

The deck will be built 4 m out from the house and 11 m wide.

 

[joflopp]

If we entertain the idea that you want three rows of plinths (or two if you attach the first support beam to the house), you will have a span of about 2 m for the floor joists. This means you should use 45x145 for the floor joists if they are placed at c/c 600. The dimension of the support beams depends on how closely you want to space the plinths. Let's say you take 6 plinths in each row, this gives you 2.2 m between each plinth and you can then end up at 45x170 (actually 2.15).

I have gathered some information about floor joist sizing here. Check the span table on the page so you can calculate other values.

Edit: All values are based on the wood being K18.

 

[bobbi91]

If we imagine that you want three rows of foundations (or two if you attach the first beam to the house) you will have a span of about 2 m on the floor joists. This means you should use 45x145 for the floor joists if placed at c/c 600. The dimension of the beams depends on how close you want the foundations to be to each other. If we say you take 6 foundations in each row, that gives you 2.2 m between each foundation and you can then end up with 45x170 (approx. 2.15).

I have gathered some information about floor framing dimensioning here. Check out the span table on the page to calculate other values.

Edit: All values are based on the wood being K18.

You seem to know a lot about dimensioning, I don't understand anything from the table you refer to.
But maybe you can help me
I'm going to build a deck that is 15.5 meters long and 4 meters deep. I was thinking of using 45x195 for beams and 45x145 for floor joists. The decking will be 28x120. I had in mind three rows of foundations.
How many foundations will it be, please help...........

 

[magnusss]

To complicate things even more
Here you can calculate how much timber you need.
http://www.gardinpersson.se/TIPS1.HTM

 

[MaZtoR]

You might want to consider that he only had 30 cm in height to the door. If he's going to use 195 + 145 + 28, he will have to dig the support beams into the ground.

 

[joflopp]

You might want to consider that he only had 30 cm in height for the door. If he uses 195 + 145 + 28, he'd have to dig the bärlinorna into the ground.

Oh well, minor details.
Completely missed this.

 

[joflopp]

You seem to know about sizing, I myself don't understand anything from the table you're referring to. But maybe you can help me I'm planning to build a deck that is 15.5 meters long and 4 meters deep. I thought of using 45x195 for the beams and 45x145 for the joists. The decking should be 28x120. I was thinking of having three rows of foundation piers. How many foundation piers will I need, please help...........

Will you attach the first beam to the house, or will all of them be on foundation piers? The reason I ask is because you need to know how many rows of beams there will be.

Let's assume you're not attaching to the house and instead have three rows of foundation piers, thus three beams. You’ll have 2 meters between them, making the span for the joists 2 meters. According to the table, you'll have some margin if you use 45x145 (up to 2.3 m).

If you use 45x195 for the beams, the foundation piers can be spaced a little over 2 meters apart, say 2.20. This is great for you as 8 piers with a spacing of 2.21 m would be 15.47 m.

You start by calculating how many rows of foundation piers you need. From this, you get the span of the joists. The lower table shows their dimensions. With the span in mind, you look in the upper table to see the distance you can have between the foundation piers depending on the beam's dimension (left side of the table).

But but but... These calculations assume you have wood of at least class K18 and place the joists on c/c 600 mm. I guess you'll have to order the wood from the lumberyard because they rarely have better than K12 in stock, and it usually consists only of "construction joists," i.e., wall joists in standard lengths of 2.5 meters.

 

[bobbi91]

Are you going to attach the first bearer to the house or will they all stand on plinths? The reason for my question is that you need to know how many rows of bearers there should be.

Let's imagine that you do not attach to the house but go with three rows of plinths and thus three bearers. Then you get 2 meters between them. Thus, the span for the floor joists is 2 meters. According to the table, you have some margin if you use 45x145 (up to 2.3 m).

If you use 45x195 as bearers, you can have the plinths just over 2 meters apart, say 2.20. This will be great for you since 8 plinths with a spacing of 2.21 m becomes 15.47 m.

You start by calculating how many rows of plinths you need. From that, you derive the span of the floor joists. The lower table shows their dimension. With the span in mind, you look at the upper table to see what distance you get between the plinths depending on the bearer's dimension (left side of the table).

But but but... These calculations apply if you have timber of at least class K18 and lay the floor joists at c/c 600 mm. I guess you have to order the timber from the lumberyard because they very rarely have better than K12 at home, and it's usually just "building studs," i.e., wall studs in finished lengths of 2.5 meters.

Thanks for the quick reply. I will not attach the bearer to the house facade but there will be a row of plinths there.
Regarding the K classification, what happens if you have K12 classified timber? The pressure-treated timber I plan to buy is classified as G4-3 ????

 

[joflopp]

If I understand this brochure correctly, G4-3 is an example of trade sorting and K18 (or C18 as it is called according to the standard, K is the old Swedish standard) is a class under strength grading.

With C14/K12 instead of C18/K18, you can decrease the spans by about 10%, or alternatively calculate with a lower uniform load than 250 kg per square meter before the floor starts to sag.

Edit: If you find G4-0-G4-2, it's classified as C14/K12.
In the lowest strength class for structural timber, C14/K12, in addition to sort T0 according to SS 23 01 20, trade sorted timber in sort G4-2 according to SS-EN 1611-1 or according to the "Blue book," sort B, is included.

 

[Danne_83]

You might want to consider that he only had 30 cm in height to the door. If he's going to use 195 + 145 + 28, he'll have to dig down the support beams into the ground.

Or use joist hangers.

 

[Västerhaninge 17]

The pressure-treated timber I saw at Bauhus 45*170 was classified as K24, according to the staff
Isn't K24 usually marked with that, those are the beams in my house.

I need to attach the first main beam to the house