Blog Archives

REPOINTING MORTAR JOINTS

Posted by on 17/ 11/ 15

Even materials as durable as brick and mortar break down in time, most commonly near the top of a wall or chimney, where masonry is most exposed to the elements. Often, the struc­ture wasn’t capped or flashed properly. If the bricks are loose, remove them till you reach bricks that are solidly attached. If joints are weathered but bricks remain firmly attached, repoint (or tuck-point) the joints by partially cutting back the mortar, adding new mortar, and shaping the joints. If the brick is painted, see "Stripping Painted Brick,” on p. 191.

Finally, if vertical or diagonal cracks run through several courses, there may be under­lying structural problems, which must be corrected before repointing. In this case, consult a structural engineer.

Raking old mortar...

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Estimation of Runoff by Peak Flow Equations

Posted by on 17/ 11/ 15

Where there are no or insufficient stream-gauging records available, peak-flow methods such as the “rational method” and the Natural Resources Conservation Service (NRCS) method may be used. The rational method is the most common procedure for determin­ing the quantity of flow for the design of minor hydraulic structures. Its use in the United States dates back to the late 1800s. One of the basic design assumptions for its use is that
the rainfall intensity is uniform throughout the watershed. This assumption limits its use to relatively small watershed areas (in the neighborhood of 200 to 300 acres, or 1 km2).

The rational method is based on the simple intensity-runoff equation

Q = KCiA (5.2)

where Q = design discharge, ft3/s (m3/s)

C = runoff coefficient

i = average rainfall intensit...

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Estimation of Runoff by Statistical Methods

Posted by on 17/ 11/ 15

Estimating the peak discharge for which highway drainage structures are to be designed is one of the most common problems and biggest challenges faced by the highway engineer. The problem may be separated into two categories: (1) watersheds for which historical runoff data are available, those with gauged sites, and (2) areas for which no data are available. Gauged sites lend themselves to analysis of runoff by statistical methods, whereas ungauged sites rely upon hydrologic equations based on the hydrologic and physiographic characteristics of the watershed.

The runoff data necessary to utilize statistical methods are available through the USGS, which is the primary collector of such data. Additional data sources are given in Chapter 3 of FHWA publication HDS 2 “Highway Hydrology...

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Flood Frequency

Posted by on 17/ 11/ 15

There are two accepted alternatives for determining the design flood frequency at a specific site: (1) by policy and (2) by economic assessment. An example of an estab­lishment of a design flood frequency by policy is the Code of Federal Regulations, which specifies that the design flood for encroachment onto through lanes of interstate highways shall not be less than the 50-year discharge. Most state and local agencies have established guidelines for policy requirements of design flood frequencies...

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. . Spreading the trusses

Posted by on 17/ 11/ 15

The temporary catwalk allows you to take a truss from a bundle and move it across the walls. Pull each truss, peak first, and spread it out near its layout mark. Each truss overlaps the previous one like a fallen domino.

STEP 2 INSTALL THE GABLE TRUSS

The first truss to be installed is the gable truss (also called an end truss or a rake truss) that rests on the top plate of an end wall. This truss is usually built differently from regular trusses. Instead of having angled web pieces, these end

. . Spreading the trussesRolling roof trusses. The first truss you should nail in place is the one for the gable end. Then it’s just a matter of rolling the remaining trusses in place, setting them on their layout marks, and nailing them down. You can do this while standing on the walls or by working off a ladder...

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Weatherstripping

Posted by on 17/ 11/ 15

Подпись: INSULATION■ BY MATTHEW TEAGUE

Подпись: Durability: Good Cost: 50Ф/П. to about $2/ft. Weatherstripping

Weatherstripping

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ver time, houses settle, doors sag, and weatherstripping wears out, creating small cracks around windows and doors. These leaks can account for 20% to 40% of a home’s heat loss. As warm air escapes in winter (and cool air in summer), the good money you’ve paid for heating (or air­conditioning) disappears, too.

Various contractors can bring in high – tech detectors to determine where your house is losing heat, but doing a close in­spection on your own reveals more trouble spots than you might imagine. Adding or replacing weatherstripping around windows and doors as well as sealing door bottoms are the obvious remedies to start with.

Many types of weatherstripping are avail­able at your local home center or hardware store...

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Roof Sheathing

Posted by on 17/ 11/ 15

Roof sheathing is placed on top of roof fram­ing members and under the roofing. As with exterior sheathing, exterior-grade plywood or OSB is most commonly used for this purpose. Unlike wall sheathing, roof sheathing will be exposed to high temperatures and will there­fore be subject to more intense outgassing. Roof sheathing usually has less time to air out in place since it is roofed over as soon as possi­ble to avoid water damage from precipitation. We therefore recommend that plywood, if used, be stickered and aired on site. We do not recommend OSB because it can develop mold and deteriorate more rapidly if it happens to get wet...

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CREATING EXTERIOR SOFFITS

Posted by on 17/ 11/ 15

In the dry Southwest, open, exposed rafter tails are preferred. But elsewhere—especially in cold, wet locations—soffits are more popular. Eave soffits are usually vented.

There are quite a few ways to frame soffits. The easiest way is to have the truss company extend the joist chord beyond the building line to form a level overhang. This is called a raised-heel truss.

If the trusses do not have a raised heel, you can still build a sof­fit easily by sheathing the underside of the sloped rafter tails. For a level soffit, nail a long 2x to the building and sheath between it and the gutter board or subfascia. If only a fascia board is used, cut a groove near the bottom edge to support the outer edge of the soffit board...

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Mortar Types (ASTM C 270-68)*,t

Posted by on 17/ 11/ 15

Подпись: TYPE PORTLAND CEMENT MASONRY CEMENT HYDRATED LIME or LIME PUTTY AGGREGATE* M 1 1 — Not Less than 21/ 1 — fir and not more than three times the sum S 1/2 1 — of the combined 1 — >/4-2 volumes of Lime and cement used N — 1 — 1 — >1/2-11/4 O — 1 — 1 — >11/4-21/2 K 1 — >21/2-4 Подпись: Adapted from the publications of the American Society for Testing and Materials, as are the compression figures given in the text. t Parts by volume. t Measured in a damp, loose condition. TWO WAYS TO CUT BRICK

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Using a mason’s hammer, score all the way around the brick, then strike the scored lines sharply.

Such cuts will be more accurate if you place the bricks on a bed of sand.

Подпись: Using a brick-cutting tool, slice small amounts of a brick to ensure a close fit. This tool is safer and quieter than using a diamond blade in a power saw.

Mortar will remain usable for about 2 hours, so mix only about two buckets at a time. If the batch seems to be drying out, “temper” it by sprinkling a little water on the batch and turning it over a few times with a trowel. As you seat each course of bricks in mortar, use the trowel to gen­tly scrape excess mortar from joints and throw it back into the pan or onto the mortarboard. Periodically turn that mortar back into the batch so it doesn’t dry out. Don’t reuse mortar that drops on the ground.

Trowel techniques...

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Mortar Types

Posted by on 17/ 11/ 15

Mortar is usually classified according to its strength and weatherability: The table at right describes the correct proportions of ingredients for each.

► Type M has the highest compressive strength, at least 2,500 pounds per square inch (psi). This durable mix is recommended for load-bearing walls, masonry below grade, and masonry that is not reinforced with steel.

► Type S has a relatively high compressive strength (1,800 psi) and the best tensile strength of any mortar listed here; so it best resists wind and soil movement.

► Type N offers medium compressive strength (800 psi) and is suitable for all above-grade uses, including those subject to heavy weathering, such as chimney mortar.

► Type O has a low compressive strength (325 psi) and is limited to non-load-bearing, interior uses...

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