Compare stair supports — Kosour and bowstring

March­ing struc­tures in hous­es are fixed with beams. The lat­ter refers to ele­ments that are called kosour or bow­string. Both devices serve as the basis for stair steps, but the tech­nol­o­gy for their instal­la­tion is dif­fer­ent. What is the pecu­liar­i­ty of each prod­uct and is there a dif­fer­ence between them? This will be dis­cussed fur­ther.

Staircase on a bowstring: manufacturing technology, features

Stairs cre­at­ed on bow­strings are dis­tin­guished by increased safe­ty, since a pro­file made of met­al or wood 5 cm thick is used for their man­u­fac­ture. If nec­es­sary, steps are addi­tion­al­ly strength­ened with wedges, screws, etc. and installed in var­i­ous ways.

On the inner parts of the bow­string, grooves are cut into which steps and ris­ers are insert­ed. The ends of the lat­ter are lubri­cat­ed with glue, which avoids an unpleas­ant creak dur­ing the oper­a­tion of the fin­ished struc­ture. The steps are attached to the string with the help of cor­ners made of met­al or wood. Those are stuffed from the inside of the bow­string. Steps are placed on top and fixed with self-tap­ping screws or screws. Pre-drilled spe­cial holes for the caps of the fas­ten­ers.

In the process of fin­ish­ing a semi-fin­ished stair­case, the vis­i­ble part of the fas­ten­ers, as a rule, is hid­den with spe­cial wood / met­al plugs or paint­ed over to match the steps. Instead of wood­en wedges or met­al cor­ners, ply­wood ribs can also be used. They will be the sup­port for the steps.

A lad­der fixed on a bow­string has a num­ber of unde­ni­able advan­tages:

1. High degree of reli­a­bil­i­ty;

2. Ease of use;

3. Safe­ty of the struc­ture (includ­ing for sig­nif­i­cant loads);

4. Long-term preser­va­tion of the steps in clean­li­ness;

5. Ele­gant appear­ance.

As a dis­ad­van­tage, one can sin­gle out, per­haps, only a sig­nif­i­cant width of the flight of stairs. How­ev­er, giv­en the thick­ness of the bow­string, a few “extra” cen­time­ters are already includ­ed in the design.

Ladder on the stringer: manufacturing technology, features

Stairs, for which the stringer was used as the basis, are very easy to man­u­fac­ture and require min­i­mal build­ing skills (as well as a min­i­mal set of tools for work). What is a kosour? In sim­ple words, this is a load-bear­ing beam that serves as a “foun­da­tion” for the steps of the stairs, fixed on top of it with a spe­cial comb.

Unlike stairs on a bow­string, struc­tures on a stringer can have one ele­ment as a basis, or maybe sev­er­al. When cre­at­ing such prod­ucts for the home, two main meth­ods are used:

Cutouts — are made direct­ly on the body of the beam and are most often made in a tri­an­gu­lar shape.

Fil­ly — spe­cial struc­tur­al ele­ments that are fixed direct­ly on the car­ri­er beam. The steps are direct­ly attached to the fil­ly. The ele­ments are tri­an­gu­lar in shape and are mount­ed on the top edge.

Stairs on the stringer have a num­ber of advan­tages:

1. With­stand sig­nif­i­cant loads;

2. Dif­fer in a com­pact design;

3. Suit­able for lim­it­ed space.

In the man­u­fac­ture of stringers, thick sheet steel, a chan­nel, T‑beams, a hol­low pro­file (rec­tan­gu­lar sec­tion) are used. Pre­vi­ous­ly, this type of design was very pop­u­lar. They are very easy to use and make. But, since they are most often made of met­al, they require good weld­ing skills.

Stringers are made of wood 7 cm thick and 30 cm wide. The most com­mon­ly used boards are made of beech, oak and oth­er hard­woods. It is note­wor­thy that only glued boards are used for work, since a sol­id beam can crack. Dur­ing the con­struc­tion of the stairs, boards 5 cm thick and 30 cm wide are used. In addi­tion to the work­ing mate­r­i­al, you will need a saw, drill, grinder for work.

ON A NOTE. Kosoura prod­ucts are great for com­pact spaces. The width of the steps varies between 0.8–1 m and coin­cides with the width of the stairs as a whole. In a design based on a bow­string, due to the pres­ence of two load-bear­ing beams, the width of the stairs will be much larg­er.

Comparative characteristics

Tra­di­tion­al sum­ming up — our experts com­pared the kosour and the bow­string. Here’s what they got.